BIO 580 Medical Microbiology Unit 1 – The Adversaries 1
The Dynamic Nature of Infectious Disease
Lecture 1 Objectives:
Understand that infectious disease is dynamic; diseases emerge and disappear, and perhaps reemerge over time. The major diseases of our past may not be the major diseases of today. New
diseases will continue to emerge in the future. Understand the major factors that influence why a
new disease emerges, especially factors that can be influenced by human activity.
Overview of human history with infectious disease:
Year
1876
1885
191819
1928
1944
1952
1962
1967
1969
1975
1976
1977
June
1981
1983
1984
1990
1991
1993
1996
1997
1999
2002
2003
2009
Event
Koch proves that a specific microbe (Bacillus anthracis)
causes a specific disease (Anthrax)
Pasteur treats a boy post-exposure, with attenuated rabies
Pandemic of Influenza A H1N1 (Spanish Flu) kills
500,000 Americans, 50 million worldwide
Penicillium discovered to kill Staphylococcus
Penicillin introduced into general clinical practice
Staphylococcal strains demonstrate resistance to penicillin
Machupo emerges in Bolivia
Marburg terrorizes Germany
Emergence of Lassa in Nigeria
Global vaccination campaign eradicates smallpox
Emergence of Ebola in Zaire
Emergence of Lyme disease (Borrelia bergdorferi)
182 American Legionnaires get sick in Philadelphia, 29
die (Legionella pneumophilia)
Emergence of penicillin resistant Neisseria gonorrhoea
Gonorrhea triple antibiotic resistant
CDC’s Morbidity and Mortality Weekly Report describes
a curious new health problem in American homosexuals
1,000th official AIDS case documented
Causative agent of AIDS identified - HIV
Jim Henson is killed by a new stain of Streptococcus
Drug resistant tuberculosis surfaces in the US
4 children die of E. coli hemorrhagic syndrome
Sin Nombre emerges in the Four Corners area
Recognition of BSE and nvCJD
Vancomycin-resistant S. aureus reported in Japan
Vancomycin-resistant S. aureus reaches Michigan
“Bird flu”(Influenza A H5N1) in Hong Kong
West Nile seen in U.S. for first time
West Nile reaches west coast
SARS-CoV emerges
Influenza A (H1N1) – first Influenza pandemic in 40 yrs
Homework – ID microbial agent
of disease as virus (V), bacterium
(B), protozoa (P), Fungi (F)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 2
Preparation for next class meeting:
Write the take home message from today in a single sentence in the space below:
Read in the text – Introduction and Chapters 1, 2, and 3 (We will discuss the info in order
Ch. 1, 3, 2).
Terminology – Find definitions for these terms. You may use one of the on-line medical
dictionaries on our course web site
http://www.cst.cmich.edu/users/alm1ew/MM%20Index%20Page.html
Used in Lecture 1
Infectious disease - any change from a state of health in which part or all of the host body is not
capable of carrying on its normal functions due to the presence of a parasite or its products.
Parasite Attenuated –
Pandemic –
Eradicate -
BIO 580 Medical Microbiology Unit 1 – The Adversaries 3
UNIT ONE - THE ADVERSARIES
Unit One - Outline of Topics
I. Review of Microbes (viruses, bacteria, fungi, protozoa, helminths, arthropods, normal microbiota)
II. Host Defenses
A. Nonspecific Defenses
1. Defenses against entry
a. Physical
b. Chemical
c. Biological
2. Defenses of the interior
a. Complement cascade
b. Acute phase proteins
c. Interferons
d. Phagocytic cells
i. polymorphonuclear leukocytes
ii. monomorphonuclear leukocytes
e. Nonspecific cytolytic cells
B. Specific Defenses
1. T lymphocytes
a. Recognition of specific antigen (TCR and MHC)
b. Activation against a specific antigen (role of APC and TH)
c. Response to specific antigen
i. T helpers
ii. T cytotoxic
iii. T regs
2. B lymphocytes
a. Recognition of specific antigen (BCR)
b. Activation against a specific antigen (role of APC and TH)
c. Response to a specific antigen
i. Plasma cells
3. Memory cells (primary vs secondary response)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 4
Unit One - Background Terminology/Concepts – will not be covered in lecture
Obligatory Steps For Infectious Microbes:
Phenomenon
1. Entry
Step
attach and enter into body
2. Spread
local or general spread in
body
multiply
3.
Multiplication
4. Evasion
evade host defenses
5. Transmission
exit from body
6. Pathology
cause damage in host
How
evade host's natural protective and cleansing
mechanisms
evade natural barriers and immediate local
defenses
but many offspring will die in host
evade phagocytic and immune defenses long
enough for full cycle in host to be completed
leave body at a site and on a scale that ensures
spread to fresh host
not strictly necessary but often occurs
Pathogen - agent capable of causing disease
Pathogenicity – ability to cause disease
Frank pathogen= obligate pathogen– causes disease in a healthy host by direct interaction
Opportunistic pathogen- may cause disease under the right conditions
Virulence – degree or intensity of pathogenicity.
Dependent on:
1. Invasiveness – ability of organism to spread
2. Infectivity – ability of organism to leave point of entry
3. Pathogenic potential – degree pathogen causes damage
Virulence factors – individual characteristics of a specific strain of microbe that confer virulence
Colonization (esp. by bacteria/yeast) – establishment of a site of replication – dependent on
attachment
BIO 580 Medical Microbiology Unit 1 – The Adversaries 5
Symbiosis - an association of two different species of organisms.
Commensalism - one species uses the body of another species as a habitat and possibly as a
source of nutrition.
Mutualism - a reciprocal relationship between two species.
Parasitism - one species in a relationship benefits and the other does not.
------
Respiration - use electron transport chain with an external e- acceptor (like O2 or NO3) as the
terminal e- acceptor
Fermentation - no external e- acceptor, one of the substrates involved accepts the eFacultative fermenter – will respire in the presence of external electron acceptors and ferment in
their absence (Ex. Escherichia coli)
Obligate aerobe - must have O2 because only O2 can serve as the terminal e- acceptor (Ex. Bacillus
spp.)
Facultative anaerobe - will use O2 for aerobic respiration if it’s present but will switch to
fermentation or anaerobic respiration if no O2 (Ex. E. coli)
Aerotolerant anaerobe - can't use O2 as an external e- acceptor, but not killed by it.
Strict or obligate anaerobe - killed by exposure to O2 (Ex. Bacteroides fragilis)
Microaerophilic - grows optimally in presence of oxygen concentrations that are below
atmospheric concentrations (ex. the streptococci)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 6
UNIT ONE – THE ADVERSARIES
I. THE MICROBES
Objectives:
To Review:
1. important structural features of viruses
2. sequence of steps during viral infection
3. consequences of viral infections at a cellular level
4. important structural features of bacteria
5. key differences between Gram positive and Gram negative cell walls
6. clinical significance of LPS, capsules, flagella, fimbriae, and pili
7. important features of eukaryotic pathogens: fungi, protozoa, helminths, arthropods
8. distribution and significance of normal microbiota by way of clinical cases
A. VIRUSES - Obligate intracellular parasites
Common structural features
1. Genetic material - DNA or RNA, ss or ds
2. Outer coat - capsid - composed of subunits called
capsomers
Nucleic acid + capsid = nucleocapsid
Only nucleocapsid = naked
Nucleocapsid surrounded by a lipid and protein
envelope = enveloped
*Outer surfaces (capsids or envelopes) impt cause they 1st make contact w/ host
cells.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 7
Viral infection of host proceeds through several steps:
1. Entry into body of host - 4 routes
1) inhalation of droplets 2) ingestion 3) direct transfer 4) bites of arthropod vectors 2. Adsorption to target cell(s) in host – specific interaction between virus surface
molecules and receptors on target cells ***
3. Entry into target cell - 2 mechanisms
1) Fusion (enveloped)
2) Receptor-mediated endocytosis (RME)
(naked & enveloped)
Entry step ends with release of viral nucleic
acid inside host target cell.
4. Multiplication w/in the target cell (obligate
intracellular) – complex process
1) synthesis of viral mRNA
DNA viruses may use host RNA polymerase -- viral DNA viral mRNA
RNA viruses have to use viral RNA polymerases
2) translation of viral proteins in host cytoplasm using host
ribosomes – viral mRNA can displace host mRNA
3) replication of viral nucleic acid
4) assembly of nucleic acid & capsomers into new
nucleocapsids (= viral progeny)
5. Release from host cell (immediate or delayed) – 2
mechanisms
1) lysis 2) budding (acquisition of envelope) –
BIO 580 Medical Microbiology Unit 1 – The Adversaries 8
Pathology - effects of viral infection on the targeted cell
1) lysis –
2) persistence –
3) latency ( lytic) –
4) transformation –
BIO 580 Medical Microbiology Unit 1 – The Adversaries 9
CONCEPT CHECK - Viruses
In the space below, in your own words, describe in complete detail:
1) the significance of surface projection – target cell receptor interactions in
viral infections
2) the two mechanisms by which an enveloped virus may enter into a target host
cell
BIO 580 Medical Microbiology Unit 1 – The Adversaries 10
B. BACTERIA - prokaryotes
Common structural features
1. Genetic material – ds, circular DNA = “chromosome”
2. Ribosomes are only organelle – 70S (30S + 50S)
3. Cell membrane – site of many metabolic functions (e.g., respiration)
4. Cell wall – shape, rigidity, strength; impt in virulence and immunity
Compound responsible for strength of cell wall is peptidoglycan (hexose sugars +
amino acids) – unique to bacteria
BIO 580 Medical Microbiology Unit 1 – The Adversaries 11
Differences in cell wall structure - Gram positive vs. Gram negative
Gram positive
peptidoglycan layer is thick
 highly polar  hydrophilic surface
 Lipoteichoic acids = LTA
 resists activity of bile
 digested by lysozyme
 synthesis is disrupted by penicillin and cephalosporin antibiotics (more
in Unit 4)
Gram negative
peptidoglycan layer is thin, overlaid by outer membrane that contains
lipopolysaccharide and lipoprotein
 outer membrane is polar, but lipids are hydrophilic
 Lipopolysaccharide = LPS
o carbohydrates  antigenicity
o lipid A is toxic = endotoxin  induces fever, increases vascular
permeability, may result in shock. etc. (more Units 2 & 3)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 12
5. Structures exterior to the cell wall in some bacteria (more common in pathogens)
a. Capsule – high molecular weight polysaccharides  slimy and sticky
clinically relevant for 2 reasons
1) attach to a wide variety of surfaces *
2) more resistant to engulfment by host defense cells **
b. Flagella
1) allow bacteria to move
2) proteins are strongly antigenic/immune stimulating
c. Fimbriae (aka “common pili”, esp. in the Neisseria)
1) attachment (fimbriae adhesins to target cell membranes)
d. Pili (aka “sex pili”)
1) exchange of genetic info, incl. antibiotic resistance (more in Unit 4)
Bacterial infection of host proceeds through several steps:
1. Entry into body of host – 3 routes
1) direct contact
2) ingestion
3) fomites (inanimate objects)
2. Adhere to, colonize, (and possibly invade) host tissues or cells (infection may be
extracellular or intracellular)
3. Evasion of host defenses (more in Unit 2)
4. Multiplication in the host (extracellular or intracellular)
5. Pathology (more in Units 2 and 3)
1) toxins
2) host immune response
6. Transmission to new hosts – usually passive in body fluids
BIO 580 Medical Microbiology Unit 1 – The Adversaries 13
EUKARYOTIC PATHOGENS
C. FUNGI
1. Morphology


cell wall contains chitin; plasma membrane contains ergosterol
yeast vs
mold
hyphae
mycelium
Dimorphic - 2 forms – yeast and mold
2. Reproduction
mold vs
yeast
spores
division
budding
3 types of fungal infections = mycoses
1) superficial –
2) subcutaneous –
3) systemic or deep Infections are most serious in immunocompromised.
D. PROTOZOA
1. Infection
may be extracellular or intracellular
2. Evasion of host defenses
3. Reproduction
asexual in humans, sexual absent or in insect vector.
4. Transmission
bites of insects
ingestion
sexually transmitted
BIO 580 Medical Microbiology Unit 1 – The Adversaries 14
E. HELMINTHS – multicellular worms
1. Exs. tapeworms, flukes, nematodes
2. Have complex life cycles
3. Transmission
fecal-oral
ingestion of larvae in tissues
active penetration by larvae
bites of insects
F. ARTHROPODS
1. Exs. mosquitoes, biting flies, fleas, ticks, lice
2. increases potential for infection with viruses and protozoa
NORMAL MICROBIOTA = Indigenous microbiota (= Normal flora)

1012 eukaryotic cells in adult human - 1013 prokaryotic
Clinical significance
1. common contaminants of clinical specimens
Fig 8.1 and Fig 8.2
2. opportunistic pathogens
In class mini clinical cases
BIO 580 Medical Microbiology Unit 1 – The Adversaries 15
II. HOST DEFENSES
Objectives:
1. understand the multiple lines of defenses against microbial infection
2. recognize the signs of acute inflammation when presented in a clinical
context and describe how each sign of acute inflammation is generated at a
cellular/tissue level
3. compare and contrast PMNs and macrophages
4. understand the importance of direct cell-cell contact in phagocytosis and the
relationships between capsules, opsonins, and phagocytosis
5. know why/how the alternate complement cascade is activated, what the
important molecules formed are, what their function is, and what the
consequences of complement activation are
6. understand how complement and phagocytosis are integrated processes
Terminology: Use a medical dictionary to find definitions
Inflammation –
Acute inflammation –
Edema –
Erythema –
Opsonin - a molecule that attaches to cells, provides a bridge to receptors on
phagocytic cells, and enhances the rate of phagocytosis.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 1
Cells of the Immune System
(White Blood Cells = WBC = leukocytes)
Monocytes
Mononuclear
Macrophages (differentiated monocytes, found in tissues) leukocytes
(agranulocytes)
Phagocytes
Neutrophils
Eosinophils
Basophils
Mast cells (differentiated basophils, found in tissues)
Natural Killer (NK) cells
Killer (K) cells
Lymphocytes
Polymorphonuclear
leukocytes
(granulocytes)
Large Granular Lymphocytes (LGL)
Cytotoxic T cell (TC)
Helper T cell (TH)
Regulatory T cell (Tregs)
T lymphocytes (T cells)
Effector B cells/ Plasma cells
B lymphocytes (B cells)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 1
Origins of Cells of the Immune System
BIO 580 Medical Microbiology Unit 1 – The Adversaries 18
The immune system is composed of 2 arms
 innate = nonspecific – already in place, response is rapid, not as efficient
 adaptive = specific – must be induced, response is slower, highly efficient, enhances
nonspecific. Has “memory”
A. Nonspecific Defenses
1. Defenses against entry into the host (1st line defenses)
a. Physical defenses (examples)
1. epithelial cells
2. turbulence
3. shedding, scraping, flushing (saliva, urine)
4. muco-ciliary clearance (1-3 cm/hr)
b. Chemical defenses (exs)
1. acids (e.g. gastric, fatty acids)
2. enzymes (e.g. lysozyme in saliva, tears, perspiration, urine)
3. other microbicidal chemicals (e.g. zinc, dermicidin)
c. Biological defenses (exs)
1. normal microbiota – physical, competition, inhibitory substances
2. immune defense cells and molecules
2. Defenses of the interior of the host (2nd line defenses)
Inflammation
a. phagocytic cells
b. cytolytic cells
c. acute phase proteins
i. CRP
ii. interferon
iii.complement
BIO 580 Medical Microbiology Unit 1 – The Adversaries 19
Inflammation - a process that coordinates and regulates all aspects of non-specific interior
defense.
Acute inflammation is characterized by:
1. increased blood supply to the area
2. increased capillary permeability
3. accumulation of neutrophils
Signs of acute inflammation – 4 signs
1.
2.
3.
4.
Triggers of acute inflammation – 2 triggers
1. cell/tissue damage/injury  chemical “alarms”
2. cell wall components of bacteria (peptidoglycan, LTA, LPS)
How Signs of Acute Inflammation are Produced
1. release of Inflammatory Mediators (=IM; see table 9.3)
2. vaso-dilation &  blood flow 
2. endothelial cells of vessels contract 
3. plasma leaks out of vessels & into tissues = exudation 
4. swelling  pressure on nerve endings 
bradykinin 
***Increased blood flow & capillary permeability - a mechanism for white blood cells and
critical soluble factors to enter the tissues to combat microbial invaders.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 20
The Critical White Blood Cells (WBC = leukocytes)
a. Phagocytes – professional engulfing cells
2 main roles for phagocytes
1. engulf and destroy foreign matter
2. secrete chemicals (esp. cytokines)
Cytokines: (see table 11.2)
 small secreted proteins that mediate and regulate inflammation, immunity, and
hematopoiesis
 low conc., act over short distances, short duration
 receptor binding induces signal transduction and transcription and translation
2 main kinds of professional phagocytic cells
1. polymorphonuclear leukocytes (= PMN = polymorph = neutrophils) – are granulocytes 2. mononuclear leukocytes - monocytes & macrophages – are agranulocytes 1. polymorphonuclear leukocyte
 dominant cell type in early stages acute inflammatory response
 made in the bone marrow - 80 mil/min
 dominant WBC, ~5,000/ul of blood - ↑15,000-20,000/ul
 live for 2-3 days - function in anaerobic environments
 abundant cytoplasmic granules contain loads of antimicrobial enzymes and chemicals,
esp. lysozyme
 best with extracellular pathogens, esp. bacteria
2. mononuclear leukocyte
 majors players later in inflammatory process
 made in bone marrow
 in the blood - monocytes (~600/ul); in tissues - macrophages (~60,000)
 conc. in lung, liver, lymph nodes, spleen
 live for months-years
 fewer granules (acid hydrolases, peroxidase)
 one of the antigen presenting cells
 secrete lots of different proteins (incl. lysozyme, nitric oxide, cytokines, complement factors)
 best with intracellular pathogens
BIO 580 Medical Microbiology Unit 1 – The Adversaries 21
BIO 580 Medical Microbiology Unit 1 – The Adversaries 22
Process of Phagocytosis – 6 steps
1. Activation – phagocytes are circulating with the bloodstream, need to move to the site of inflammation.
a. margination
b. pavementing
c. diapedesis
2. Migration via chemotaxis – phagocytes have receptors for chemoattractant molecules, will
track a concentration gradient of these molecules to the site where they are being produced.
3-6. – illustrated in diagram
3. Attachment – phagocytosis cannot happen until the phagocyte makes direct contact with the
surface of the microbe. That direct contact is mediated by receptors on the surface of the
phagocyte.
Pathogen-Associated Molecular Patterns
Microbe - PAMP to PRR – phagocyte
Pattern Recognition Receptors
PAMP incl. LTA & LPS (table 9.2)
After PAMP-PRR interaction, macrophages secrete pro-inflammatory cytokines (TNF, IL-1)
 enhance antigen-presentation  leads to activation of Th1. We’ll talk about this later.
4. Engulfment
5. Phagosome-lysosome fusion and intracellular killing
6. Expulsion of debris
Phagocytosis - Diagram
BIO 580 Medical Microbiology Unit 1 – The Adversaries 23
Role of Opsonins in Process of Phagocytosis - Diagram
(review definition of opsonin from p. 15)
Microbe
+phagocyte
Opsonin
none
present
Interaction
Rate of Phagocytosis
BIO 580 Medical Microbiology Unit 1 – The Adversaries 24
Phagocyte Intracellular Killing Mechanisms
1. Oxygen-dependent killing (see box 9.2, p. 83) – PMN and macrophages
“oxidative burst”
Reduction
O2
NADPH
NADP
superoxide anion
hydrogen peroxide
singlet oxygen
hydroxyl radicals
O2H2O2
1
O2
OH
Reactive Oxygen
Intermediates (ROI)
Other reactive intermediates
 reactive nitrogen (nitric oxide = NO)
(macrophages)
 reactive chlorine (OCl) + myeloperoxidase
(PMN)
phagosome
membrane
2. Oxygen-independent killing compounds contained in cytoplasmic granules (see Table 14.2, p.
153)
 acid hydrolases (PMN)
 cathepsin G (PMN)
 cationic proteins (PMN, eosinophils)
 defensins (PMN)
 lactoferrin (PMN)  lysozyme (PMN, macrophage) –
 peroxidase (eosinophils)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 25
b. Cytolytic Cells
1. natural killer cells (NK) (LGL)
target - intracellular pathogens, primarily viruses
attach – by way of receptors to glycoproteins on infected cells
release - perforins (membrane channels) granzyme (apoptosis)
also secrete TNF
also – secrete -IFN, impt early source, can activate macrophages
2. basophils and mast cells
target – parasites
can be triggered to discharge cytoplasmic granules
release histamine, heparin, anaphylactic factors
3. eosinophils
target - large parasites (e.g. helminthes)
can be triggered to discharge cytoplasmic granules
release basic proteins, perforins, ROI  chemical burns
BIO 580 Medical Microbiology Unit 1 – The Adversaries 26
CONCEPT CHECK – Nonspecific defenses
Bubble Map
Characteristics unique to PMN
PMN
Shared characteristics
Characteristics unique to macrophages
Macrophage
BIO 580 Medical Microbiology Unit 1 – The Adversaries 27
c. The Critical Soluble Factors
Acute Phase Proteins
 Plasma proteins – proteins that increase in concentration 2-100X during the acute phase of
an infection, in response to cytokines (IL-1, TNF).
i.. C-reactive protein (CRP) – produced by liver - uses pattern recognition to bind to bacteria
 acts as an opsonin
 activates complement cascade
 often used to monitor inflammation
ii. Interferons
Interferons – first recognized because they interfere w/ viral replication
3 classes of Interferons:
1.  - produced by leukocytes (WBC) – anti-viral - prod w/in 24h
2.  - produced by fibroblasts and other cells – anti-viral - prod w/in 24 h
3.  - produced by NK and esp. T lymphocytes – anti-viral and involved in cell-cell
communication.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 28
iii. Complement - activation of the alternate cascade (= properdin pathway) - A group of 20
serum proteins – form an enzymatic cascade
C3 (most abundant, prod. by liver cells)
C3a
C3b
Factor B
C3bB
Factor D
--------------------------------------------------------------------------------------------------------------------C3bBb = C3 convertase
C3
C3a
C3
C3b
C3a
C3b
C3bBb3b = C5 convertase
C5 (prod by macrophages)
C5a
C5b
C5b67
C5b678 multiple 9
cell lysis
Microbe
+phagocyte
Opsonin
none
C3b
CRP
Interaction
Rate of Phagocytosis
BIO 580 Medical Microbiology Unit 1 – The Adversaries 29
Integration of Nonspecific Defenses
1. Stimulus
a. cell/tissue injury
inflammatory mediators released
b. microbial surface polysaccharides
2. Within seconds to minutes
a. acute inflammation begins
 vaso-dilation of capillaries  increases blood flow to/volume at the site
 increased vascular permeability  exudation of plasma, cells, and proteins
b. acute phase proteins increase in concentration
c. alternate complement cascade is activated
 C3a and C5a  mast cell degranulation
maintains vaso-dilation/vascular permeability
 C5a attracts phagocytes from vasculature
 C3b and C5b bind to cell surfaces
 C3b opsonin
3. Minutes to hours
a. PMNs arrive in huge number and encounter cells opsonized by C3b and CRP 
phagocytosis is enhanced.
4. Hours to days
a.
Interferons are produced
b. NK arrive
c.
Macrophages arrive
BIO 580 Medical Microbiology Unit 1 – The Adversaries 30
SUMMARIZE – Nonspecific Defenses
List the Nonspecific Interior Defenses important against Bacteria
List the Nonspecific Interior Defenses important against Viruses
CONCEPT CHECK – Nonspecific defenses
Draw a concept map that illustrates the integration of complement and phagocytosis
BIO 580 Medical Microbiology Unit 1 – The Adversaries 31
CONCEPT CHECK - Nonspecific Host Defenses
Steve, a college student, was backpacking in a remote wilderness region with some friends.
While pitching a tent, he tripped and fell. In an attempt to break his fall, he extended his arms
and sustained a puncture wound to his right palm. Although the wound was painful and bled for
a short time, it didn’t appear to be serious, and Steve fell asleep that night unconcerned.
By the next morning, however, Steve noticed that the tissues immediately surrounding his wound
were red, swollen, and warm. A round area about 1 inch in diameter really looked abnormal
compared to the rest of his hand. The affected area was also painful, especially when he touched
it or bumped it. After hiking all day, the sore hand was even more painful, and a thick yellow
discharge oozed from the open wound. Steve felt unusually tired, his body ached, and a brief
chill made him aware that he was getting a fever. His friends helped him elevate his arm and
applied warm compresses to his palm, hoping that he would feel better in the morning.
1. List the nonspecific defenses against entry that are relevant to skin.
2. How were Steve’s skins defenses against entry overcome?
3. List the nonspecific interior defenses that would become activated in this case of bacterial
invasion.
4. What are the signs in the case history that Steve is experiencing an inflammatory process? List
them.
5. Describe the mechanisms at the cellular/tissue level that cause each of the signs of
inflammation listed in 4 above?
BIO 580 Medical Microbiology Unit 1 – The Adversaries 32
Supplemental information FYI
Blood (modified from Wikipedia)
Blood accounts for 8% of the human body weight. The average adult has a blood volume of
roughly 5 liters (1.3 gal), composed of plasma and several kinds of cells; these formed elements
of the blood are erythrocytes (red blood cells; RBC), leukoytes (white blood cells; WBC), and
thrombocytes (platelets). By volume, the red blood cells constitute about 45% of whole blood,
the plasma about 54.3%, and white cells about 0.7%.
Cells:
One microliter of blood contains:
 4.7 to 6.1 million (male), 4.2 to 5.4 million (female) erythrocytes. The proportion of blood
occupied by red blood cells is referred to as the hematocrit, and is normally about 45%.
 4,000–11,000 leukocytes. White blood cells are part of the immune system; they destroy and
remove old or aberrant cells and cellular debris, as well as attack infectious agents and
foreign substances.
 200,000–500,000 thrombocytes: Platelets are responsible for blood clotting (coagulation).
They change fibrinogen into fibrin. This fibrin creates a mesh onto which red blood cells
collect and clot, which then stops more blood from leaving the body and also helps to prevent
bacteria from entering the body.
Plasma:
About 55% of whole blood is blood plasma, a fluid that is the blood's liquid medium, which by
itself is straw-yellow in color. The blood plasma volume totals of 2.7–3.0 liters (2.8–3.2 quarts)
in an average human. It is an aqueous solution containing 92% water, 8% blood plasma proteins,
and trace amounts of other materials. Plasma circulates dissolved nutrients, such as glucose,
amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins), and removes
waste products, such as carbon dioxide, urea, and lactic acid.
Other important components include:
 Serum albumin
 Blood-clotting factors (to facilitate coagulation)
 Immunoglobulins (antibodies)
 lipoprotein particles
 Various other proteins
 Various electrolytes (mainly sodium and chloride)
The term serum refers to plasma from which the clotting proteins have been removed. Most of
the proteins remaining are albumin and immunoglobulins.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 33
Constitution of normal blood
Parameter
Value
hematocrit
45 ± 7 (38–52%) for males
42 ± 5 (37–47%) for females
pH
7.35–7.45
base excess
−3 to +3
PO2
10–13 kPa (80–100 mm Hg)
PCO2
4.8–5.8 kPa (35–45 mm Hg)
HCO3
21–27 mM
oxygen saturation Oxygenated: 98–99%
Deoxygenated: 75%
Saliva (modified from Wikipedia) - Produced in salivary glands, human saliva is 98% water, but
it contains many important substances, including electrolytes, mucus, antibacterial compounds
and various enzymes
It is a fluid containing:
 Water
 Electrolytes: (sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, iodine)
 Mucus. Mucus in saliva mainly consists of mucopolysaccharides and glycoproteins;
 Antibacterial compounds (thiocyanate, hydrogen peroxide, and secretory IgA)
 Epidermal growth factor or EGF
 Various enzymes. There are three major enzymes found in saliva.
o α-amylase - starts the digestion of starch and lipase fat.
o lingual lipase
o Antimicrobials that kill bacteria: **
 Lysozyme
 Salivary lactoperoxidase
 Lactoferrin
o Proline-rich proteins (function in enamel formation, Ca2+-binding, microbe killing and
lubrication)
o Minor enzymes
 Cells: Possibly as much as 8 million human and 500 million bacterial cells per mL. The
presence of bacterial products (small organic acids, amines, and thiols) causes saliva to
sometimes exhibit foul odor.
 Opiorphin, a newly researched pain-killing substance found in human saliva.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 34
Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are a family of
enzymes that damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between
N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between Nacetyl-D-glucosamine residues in chitodextrins. Lysozyme is abundant in a number of
secretions, such as tears, saliva, human milk, and mucus. It is also present in cytoplasmic
granules of the polymorphonuclear neutrophils
(PMN).
Urine is approximately 95% water. The other components of normal urine are the solutes that
are dissolved in the water component of the urine. These solutes can be divided into two
categories according to their chemical structure (e.g. size and electrical charge).
Organic molecules. These include:
 Urea – Makes up 2% of urine. Urea is an organic compound derived from ammonia and
produced by the deamination of amino acids. The amount of urea in urine is related to
quantity of dietary protein.
 Creatinine - Creatinine is a normal constituent of blood. It is produced mainly as a result of
the breakdown of creatine phosphate in muscle tissue. It is usually produced by the body at a
fairly constant rate (which depends on the muscle mass of the body).
 Uric acid - Due to its insolubility, uric acid has a tendency to crystallize, and is a common
part of kidney stones.
 Other substances/molecules - Example of other substances that may be found in small
amounts in normal urine include carbohydrates, enzymes, fatty acids, hormones, pigments,
and mucins (a group of large, heavily glycosylated proteins found in the body).
Ions These include:
 Sodium
 Magnesium
 Sulfates
 Potassium
 Calcium
 Phosphates


Chloride
Ammonium
BIO 580 Medical Microbiology Unit 1 – The Adversaries 35
B. Specific Defenses
Objectives:
1. understand how the appropriate lymphocytes are selected and activated and amplified
2. understand how immune cells “talk” with each other via cytokines
3. compare and contrast activation and response of T and B lymphocytes
4. compare and contrast the activation and response of Th1, Th2, and TC
5. understand the interactions between nonspecific and specific host defenses
6. understand how the specific immune response focuses the nonspecific response
7. understand the power of the secondary (anamnestic) immune response




= adaptive = acquired
3rd line of defense – only one with antigenic memory
based on lymphocytes
feedback into the nonspecific defenses – enhance the effectiveness of the non-specific
defenses
Specific immune system has to:
1. recognize
2. activate
3. respond
1. Overview
a. Recognition of antigen
A specific interaction between an antigen and a receptor
Anti gen
Antigens incl:
***proteins (incl. proteins + carbos or lipids) (T and B)
***complex polysaccharides (B only)
***nucleic acids (B only)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 36
Full activation of the specific defenses involves several different types of immune cells working
in concert:
 non-specific cells (antigen-presenting cells)
 specific cells (lymphocytes)
Antigen-Presenting Cell (APC)
Specialized cells that present microbial peptides (antigenic determinants) in a way that can be
recognized by lymphocyte receptors.
Most significant: dendritic cells (tissues) > macrophages > B cells
Antigenic determinant (= epitope) – a certain stretch of peptides from a larger microbial antigen
 linear or conformational
 small in size
2 main types of Lymphocytes
 T lymphocytes (T cells)
 B lymphocytes (B cells
Lymphocyte receptors (R)
 constant region – transmembrane
 variable region – interacts with microbial peptide
General Overview of Antigen Presentation - Diagram
Presentation of antigenic determinant by an APC to a lymphocyte occurs in draining lymph
nodes (surfaces, tissues) or spleen (blood)
Initiates a chain of events that transforms a small, resting, naïve lymphocyte into a highly active,
functional lymphocyte (more later)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 37
b. Activation – from all the antigen naïve lymphocytes,
selection of lymphocytes with complementary receptor that matches
specific microbial antigenic determinant
1. receive and secrete cytokines
2. undergo proliferation = clonal expansion
1104 – 105 - occurs in lymphoid organs
Results in an expanded population of immature effector
lymphocytes
3. differentiate into functional sub-types
effectors – fight this time
memory – reserves, to be deployed in the future
c. Response – of activated effector sub-types
activated (= primed) effector T lymphocytes either:
1. kill infected cells
2. coordinate and regulate immune response
activated effector B lymphocytes (called plasma cells)
secrete antibodies
BIO 580 Medical Microbiology Unit 1 – The Adversaries 38
2. Add in specifics
T Lymphocytes
2 categories of T cells by surface marker called Cluster Determinant
1. CD4 - 2 functional types
1) T helper cells = TH - regulate the immune system by increasing the response ( by
activating other immune cells).
a) Subset Th1
b) Subset Th2
2) T regulatory cells (=Tregs) - regulate the immune system by the response
2. CD8 =T cytotoxic cells =TC = CTL- kill cells infected w/ intracellular pathogens
a. Antigen Recognition by Antigen-Naïve, Resting T lymphocytes
*T cell receptor interacts with microbial (foreign) antigenic determinant complexed with a self
antigen
Self antigens – Major Histocompatibility Complex (MHC) proteins – protein molecules on the
surface of cells that mark them as “cells”.
2 classes of MHC
Class I - on the surface of all nucleated host cells
Class II – on the surface of APC
THR - recog. antigenic determinant complexed w/ Class II MHC + co-stimulatory interactions
(depend on who the APC is)
TCR - recog. antigenic determinant complexed w/ Class I MHC + co-stimulatory interactions
b. Activation of T lymphocytes – 3 steps
1. Receive cytokines from APC
ex. IL-1 from macrophage
2. ↑ # of IL-2R and secrete/receive IL-2  proliferation
Results in an expanded set of immature effector lymphocytes,
all with same receptor for antigenic determinant complexed
to MHC II (will all recognize the same microbial threat)
3. Differentiation into effector and memory T cells
Tc, and NK
BIO 580 Medical Microbiology Unit 1 – The Adversaries 39
c. Response of Effector T Lymphocytes
Each category of effector T cell has a unique response:
regulating the immune response = immunoregulation
 enhance response - TH
subset Th1 – secretes IL-2 – stimulates Tc proliferation & maturation. Secretes -IFN – activates
effector TC , activates macrophages and NK to kill their intracellular pathogens;
(down regulates Th2)
subset Th2 – secretes IL-4 – stimulates B cell proliferation & differentiation into plasma
cells; (down regulates Th1)
 suppress response - Tregs
OR
direct cell killing = cytotoxicity – TC
secrete perforin  transmembrane channels
secrete granzyme  apoptosis
also secrete TNF
also secrete -IFN (activates NK and macrophages)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 40
Integration via Lymphocyte Recognition, Activation, and Response - Diagram
BIO 580 Medical Microbiology Unit 1 – The Adversaries 41
B Lymphocytes
a. Antigen Recognition by B Lymphocytes
Receptor interacts with microbial (foreign) antigen alone – receptor does not interact with MHC.
Can present antigen to Th2
b. Activation of B Lymphocytes
1.IL-2 from subset Th2  clonal expansion (= proliferation)
2.IL-4 from subset Th2  differentiation into effector (= plasma) and memory B cells
c. Response of Effector B lymphocytes (=Plasma Cells)
Secrete Antibody (Ab) at the rate of 1,000 molecules/min.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 42
Antibody Structure - Diagram
BIO 580 Medical Microbiology Unit 1 – The Adversaries 43
Actions of Antibody Molecules – focus the non-specific
1. bind to microbial antigen – interfere with receptor interaction for any microbe that uses specific
attachment sites = neutralizing
***2linking a bacterium to a phagocyte = opsonization (followed by phagocytosis)
Microbe
+phagocyte
Opsonin
none
C3b
CRP
Ab
C3b + Ab
Rate of Phagocytosis
-/+
+
+
3. linking many small antigens together = agglutination (followed by phagocytosis)
4. complement activation - classical pathway (followed by either opsonization and phagocytosis
or lysis) (notes p.45)
5. ADCC - antibody dependent cellular cytotoxicity (notes p. 47)
BIO 580 Medical Microbiology Unit 1 – The Adversaries 44
Activation of Classical Complement Cascade - Diagram
C4
C4a
C1
C4b
C2
C2a
C2b
C4b2a = C3 convertase
C3
C3a
C3
C3b
C3a
C3b
C4b2a3b = C5 convertase
C5
C5a
C5b
C5b67
C5b678 multiple C9
Fill in:
Triggers –
Important molecules –
Consequences Timing –
Complement activation enhances phagocytosis and inflammation and leads to cell lysis.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 45
Classes of Antibody Molecules
Antibody = Immunoglobulin (Ig) – proteins found in fluids in the body
5 Classes:
Class
Structure
%
IgG
monomer
75-80
IgA
15-21
IgM
monomer
dimer
pentamer
IgD
monomer
<1
IgE
monomer
0.01
6-7
Location
serum, extra vascular
spaces, crosses placenta
serum, tears, saliva, mucus,
colostrum
serum, 1st made by virgin
B cells, 1st made by fetus
low levels in serum
B cell surface
skin
RT fluid
Roles
fix complement
opsonin
neutralizing
fix complement
agglutinating
? regulate clonal
expansion?
bind to mast cells &
basophils
Feedback into the non-specific defenses; esp. complement, phagocytosis
Function of Memory Lymphocytes – the reserves - stronger response on secondary exposure to
antigen
1. are more memory cells then there were naive cells at the beginning of the primary response
2. were primed to antigen during primary response so are able to bind more strongly to APC
3. antigen-primed memory B cells differentiate into plasma cells more quickly
4. memory is usually long-lasting, years
Primary versus Secondary (= anamnestic) Response
BIO 580 Medical Microbiology Unit 1 – The Adversaries 46
Misc.
Killer (K) cells
Rely on antigen specific antibodies BUT interact with antibody in a nonspecific way, by way of
the Fc. Participate in the non-specific interior defenses:
K cells include:
NK
macrophage
eosinophil
All K cells have receptors for Fc of antibody molecules
K cells bring about lysis of the antibody-coated cell in a process called antibody-dependent
cellular cytotoxicity (ADCC); for pathogens that are too big to phagocytize.
BIO 580 Medical Microbiology Unit 1 – The Adversaries 47
SUMMARIZE – Specific Defenses
Fill in table
Cytokine or proinflammatory
mediator
IL-1
IL-2
IL-4
IFN 
IFN 
IFN 
TNF
Complete:
TH
function –
recognition –
activation –
response – Th1 -- Th2 –
TC
function –
recognition activation –
response –
Treg
function –
recognition activation –
response –
B Lymphocyte
recognition –
activation –
response –
Secreted by:
Acts on:
Functions to:
BIO 580 Medical Microbiology Unit 1 – The Adversaries 48
SUMMARIZE – Specific Defenses
List the Specific Interior Defenses important against Bacteria
List the Specific Interior Defenses important against Viruses
CONCEPT CHECK – Specific defenses
Concept Map
Draw a concept map that illustrates the connections between the specific and nonspecific
immune responses
BIO 580 Medical Microbiology Unit 1 – The Adversaries 49
CONCEPT CHECK – Specific Defenses
Continuation of the Case of Steve
When Steve. awoke on the second morning, his condition was clearly deteriorating. The first
thing he noticed was that the small area of redness and swelling had extended to include his
entire hand, with the margin of redness now visible just above his wrist. Faint red streaks had
appeared along the inner part of his arm and tender lumps were noticeable below his elbow and
under his arm. His fever seemed higher than the night before, and he felt too weak to walk.
Steve was too sick to travel, and his friends figured that it would take several days to return with
medical help. They decided to stay in camp and let Steve rest. Over the next couple of days
Steve and his friends were relieved to find him gradually improving. The red area did not
advance past his forearm. Although the hand remained painful and swollen, he felt less tired and
the fever was gone. Four days after the first presentation of inflammation, when he was a little
better, they headed back and took Steve to the nearest emergency room.
The doctor diagnosed a presumed bacterial infection and prescribed a broad-spectrum antibiotic
that was likely to be effective against the unknown infecting bacterium. The medication was
taken orally, and Steve was sent home. The redness and swelling of the hand subsided gradually
over the next two weeks.
1. What were the tender swellings that Steve noticed behind his elbow and under his arm and
why were they swollen?
2. Steve began to improve within 4-5 days of initial infection. How could antibody have played
a role in resolving Steve’s symptoms within this time frame?
3. What functions did these antibodies play in the immune response to Steve’s bacterial
infection?