Phagocytes
Killer T-cells
Macrophages
Natural Killer Cells
Immune system
 Function = destroy & remove
all “non-self”
(pathogens/invaders)
 Often considered part of the Circulatory
System
 2 Types of Body defenses =
1. Non-specific
2. Specific
I.
Non-Specific Body Defenses
 Effective against all infections
A. First line of defense – Skin
1. Physical barrier
prevents entry of pathogens
(micro-organisms)
2. Must be unbroken to be effective
3. Skin is acidic, plus oil & sweat
glands
inhibit bacterial growth
Non-Specific Body Defenses
B. Mucus Membranes
1. Location:
respiratory,
digestive,
urinary,
& reproductive tracts
2. F(x) = trap pathogens & debris
Non-Specific Body Defenses
C. Hairs (nasal passages)
F(x) = trap pathogens & debris
Nose hairs
Non-Specific Body Defenses
D. Cilia
- throat
(upper respiratory tract)
- trap pathogens & debris
Non-Specific Body Defenses
E. Cellular & Chemical defenses

Activated when
outer defenses
are breached
1. Phagocytes
a. Cells that recognize “non-self”, i.e. foreign
particles or invaders
Phagocyte eating dying cells
1. Phagocytes
b. E.g. White Blood Cells
(WBCs) such as
neutrophils &
macrophages
c. Travel to infection site via
circulatory system
(bloodstream) or
lymphatic system
d. Can squeeze through
intercellular spaces
1. Phagocytes
d. Engulf (“eat”) invaders / foreign debris
e. Release lysosomes to dissolve invaders /
foreign debris
Phagocytes &
yersinia pestis
2. Natural Killer Cells (NK cells)
a. WBCs – police the blood
& lymph
b. Bind to membrane of
invader,
release
chemicals,
lyse cell
3. Inflammatory Response
a. Inflammation = heat, redness, swelling due
to fluid build-up, pain
b. Localized response at site of tissue
damage
c. Prevents spread of damaging agent
Inflammatory Response
Inflammatory Response
4. Fever
a. Systemic response to infection
b. Stimulates phagocytes (WBCs) to work
c. Heat kills many pathogens
5. Interferon
a. Secreted by virus-infected cells
b. Stimulates non-infected cells to make
proteins that block viral protein synthesis
c. Slows infection to allow specific defenses to
begin working
d. Activates macrophages to “eat” (non-self)
viral invaders
II Specific Body Defenses
(against a specific pathogen)
 General Information



Create Immunity = highly specific
resistance to disease
Particular invader recognized, switches
on immune response
Specific Invader is remembered so that
future invasions can be immediately
fought
II Specific Body Defenses
B. Antigen
1. Irritant or pathogen
2. Stimulates formation of antibody
C. Antibody
1. Forms due to exposure to a specific antigen
2. Produced by B-cells

i.e. Bone marrow  makes B-cells,
which make specific
antibodies
3. Binds to antigen to mark it for
destruction by
macrophages
C. Antibody
4. Found in plasma & all body
secretions
5. Once present, allows immediate
immune response to pathogens
6. (memory B cells remember
pathogen, so next exposure brings
rapid response)
Antigen Antibody Response
Antibodies
Antigens
D. Macrophages
- destroy cells marked by antigen-antibody
complex
E. Helper T-cells
 Activate other T-cells
 Attract Killer T cells
& macrophages to an
antigen
F. Killer T-cells
 – directly attack & kill pathogens, release
cytotoxic chemicals to lyse cells
G. Suppressor T-cells
 - stop immune response when antigen
is successfully overcome
Notice !
Non-specific
and
Specific Defenses
work together
to protect the body
from disease-producing
pathogens
Origins of cells
B
cells mature in bone tissue
T cells mature in thymus
tissue
Types of Immunity (3)
– vaccinated against or
recovered from the disease
(immunity permanent or
long-lasting)
1. Active
Types of Immunity (3)
2. Passive –
antibodies
produced by another organism
injected into body
(temporary protection
against the disease)
Types of Immunity (3)
3. Cell Mediated – killer T-cells
attack any cell not marked with
a special protein
(i.e. cells that are “non-self”)
Cell-mediated Immunity
Immune system
Vaccine= living or inactivated organism
used to induce specific immunity
 Can be made from antibodies, or cause
antibodies to be made
Immunization= process that increases
an organism’s rxn to antigen & therefore
improves its ability to resist or overcome
infection