BODY DEFENSE SYSTEM
animal/human must defend , against intruders;pathogen…??..bacteria, virus, fungi, pathogen from
air, water, food, environment….
Body defense system/immunity?
DEFINITION:
ability of an organism to recognize and defend itself
against pathogen
resisting the attack of many dangerous organisms.
IMMUNOLOGY
Chapter 1:
Body defense system
Chapter 2
Innate Host Defenses
Body defense
system
Adaptive /acquired
immunity
Innate immunity
Internal
External
Immune response
Physical
mechanical
Biological
Cellular
Molecular
* DEFINITION: Innate and Adaptive immunity
Host defenses that produce resistance against infection can be
adaptive or innate
* Innate defenses:
agent
those that act against any type of invading
* Adaptive defenses:
respond to particular agents called
antigens (e.g. viruses and pathogenic bacteria)
Only when our resistance fails do we become susceptible to
infection by pathogens
* Adaptive Defenses
* Respond to antigens by producing protein
antibodies
* Also involve the activation of the lymphocytes
* Lymphocytes:
specific cells of the body’s
immune system
* Antibody and cellular responses are more
effective against succeeding invasions by same
pathogen than against initial invasions
*Innate Defenses
1.
2.
3.
4.
5.
6.
7.
Physical barriers
Chemical barriers
Mechanical Barrier
Cellular Barrier
Inflammation
Fever
Molecular defenses
INNATE IMMUNITY
ADAPTIVE IMMUNITY
Non specific- acts against many
organism
Specific- respond to the specific
antigen
Present from birth
Acquired- usually by having disease/
vaccination
Heredity
not
Does not become more efficient
after more exposure
The immune system efficiency
increased and memorized after
exposure
Various types of defense mechanism
Involves mostly lymphocytes cell,
that produces B cell and T cell
1. Physical Barriers
* Skin and mucous membranes protect your body
and internal organs from injury and infectious
agents
* These two physical barriers are made of cells that
line body surfaces and secrete chemicals
* human beta-defensin-2 on human skin destroys
pathogens by poking holes in bacterial membranes
* Mucosa covers those tissues and organs of body
cavity exposed to exterior
2. Chemical Barriers
* High salt content of sweat inhibits bacteria from
growing
* Sweat and sebum produced by sebaceous glands
have low pH that inhibits growth of bacteria
* Acidic pH of stomach is a defense against intestinal
pathogens
* Lysozyme: present in tears, saliva, and mucus,
cleaves peptidoglycan linkage in bacterial cell wall
3. MECHANICAL BARRIER
FUNCTION:
- PREVENT/FLUSH INVADING MICROBES IN
DIFFERENT TYPE OF MECHANICAL WAY
• Hair and mucus- nasal, respirotary system
• Coughing and sneezing
• Urinary flow- remove microbes in urinary tract
• Tears and saliva – flush bacteria from eyes and
mouth
• Vomitting and diarrhea- flush bacteria from
digestive tract
4. Cellular Defenses – Defensive Cells
* Blood consists of about 60% liquid called plasma and 40%
formed elements (cells)
* Formed elements:
erthyrocytes, platelets, and leukocytes
* Leukocytes are defensive cells important to adaptive and
innate host defenses
Formed cellular elements of the blood
* Granulocytes
*
*
1.
2.
3.
4.
5.
Have granular cytoplasm and an irregularly shaped,
lobed nucleus
Include:
Mast cells: prevalent in connective tissue, release
histamine, and associated with allergies
Basophils: release histamine which helps initiate
inflammatory response
Eosinophils: present in large numbers during allergic
reactions
Neutrophils (polymorphonuclear leukocytes):
phagocytic cells that guard skin/mucous membranes
against infection
Dendritic cells: phagocytic cells that resemble nerve
cells
* Agranulocytes
*
Lack granular cytoplasm with round nuclei
*
1.
Include:
Monocytes: phagocytic cells derived from
myeloid stem cells
Lymphocytes: derived from lymphoid stem
cells and contribute to adaptive host
immunity
2.
*
Lymphocytes circulate in blood and are
found in lymph nodes, spleen, thymus and
tonsils
* Phagocytes
* Cells that literally eat or engulf materials
* Monocytes, dendritic cell, neutrophils,
eosinophils,
* Patrol, or circulate through body, destroying
dead cells and cellular debris
* Guard the skin/mucous membranes against
invasion by microorganisms
* Macrophages(formed from monocytes): “big
eaters” that destroy not only microorganisms
but also larger particles
* The Process of Phagocytosis
*
Phagocytes digest and destroy invading microbes and
foreign particles by a process called phagocytosis
*
Phagocytic cells must:
Find
Adhere to
Ingest
Digest the microorganisms
Phagocytosis of two bacterial cells by a neutrophil
* Chemotaxis
*Phagocytes in tissues first must recognize invading
microorganisms
*pattern recognition receptors (PRRs) on the phagocytic
cells recognize molecular patterns unique to pathogen
*Phagocytes release cytokines that have specific roles in
host defenses
*Chemokines:
-A class of cytokines that attract additional phagocytes
to site of infection
* Adherence and Ingestion
* The ability of the phagocyte cell membrane to bind to
specific molecules on the surface of the microbe is
called adherence
* Antiphagocytic capsule:
the most common means by
which bacteria avoid phagocytosis
* Complement system:
coat microbes with antibodies to
aid phagocyte in adherence
* Phagosome:
pseudopodia fuse and enclose
microorganism within this cytoplasmic vacuole
* Digestion
*
Phagocytic cells have several mechanisms
for digesting and destroying ingested
microbes
*
Phagolysosome: lysosomes with digestive
enzymes fuse with phagosome membrane
*
Macrophages use other metabolic products
to kill ingested microbes:
Oxygen to form hydrogen peroxide
Nitric oxide and superoxide ions
1.
2.
* What if the intruder is larger than the
Macrophage/neutrophils?
The killing need to be done extracellularlly by…
Eosinophils- excreting toxic enzymes (MBP) –kill worm
Natural killer cell- secrete cytotoxic proteins that kill
intracellular
*Extracellular killing
* Complement
*
Refers to a set of more than 20 large
regulatory proteins that play a key role in
host defense
*
General functions of the complement system
are:
Enhance phagocytosis
Lyse pathogens directly
Generate peptide fragments that regulate
inflammation and immune responses
1.
2.
3.
*
Works as a cascade: a set of reactions that
amplify some effect
5. Inflammation
*
The body’s defensive response to tissue
damage from microbial infection
*
1.
2.
3.
4.
Characterized by signs:
an increase in temperature
redness
swelling
pain at infected or injured site
Steps in the
process of
inflammation and
subsequent
healing
6. Fever
•
The elevation of body temperature to kill invading
agents and/or inactivate their toxic products
HOW?
Raises temperature above opt. temp. of pathogens
Microbial enzymes or toxins is inactivated
Increase immune response
Phagocytosis is enhanced
Antiviral interferon production is increased
Fever makes patient lie to rest..
Increased breakdown of lysosomes causing death of
infected cell and microbes.
7. Molecular Defenses
*Involve the action of interferon and
complement
*Interferon:
interfered with viral replication in
other cells
*Humans have three groups of interferon
(alpha, beta, and gamma)
*Antiviral enzymes
The mechanism by which interferons alpha and beta act
A Summary of the body’s nonspecific defenses