1. External and Internal Defenses
Immune System
External and Internal
Defenses

2. * Items described in last slide

3. External Defenses 1) Skin…waterproof layer dead cells
2) Linings of body tubes/cavities
a) sticky mucus w/ lysozyme enzymes
b) ciliated cells in resp. tract
c) stomach acid & bile salts
d) urine & vaginal low pH
3) Neutral/beneficial bacteria population

4. Internal Defenses II innate immunity =
present at birth, always present
II aquired/adaptive immunity =
activated by microbes
a) Require self-recognition
(membrane proteins)
b) only present in Verts

5. I. Innate Immunity A) Phagocytic Cells B) antimicrobial proteins
C) inflammatory response
D) Systemic response

6. A) Types of Phagocytic cells
1) neutrophils – most abundant (1st responders)
2) macrophages – largest
3) eosinophils – poison multi-cellular parasites
4) dentritic cells – activate acquired immunity
a) digest pathogen into pieces
b) bind pathogen pieces to MHC receptors*
c) display pathogen on cell membrane
d) attract helper T cells*
e) helper T cells activate aquired imm. resp.

8. B) Antimicrobial Proteins
1) interferon ά and β
secreted by virus-infected cells
help neighboring cells inhibit viral reproduction
2) complement system = 30 serum proteins
microbe presence triggers cascade
cascade activates complement system
system causes microbe to lyse
also trigger inflammation
(may also be activated by antibodies*)

9. C) Inflammation Triggered by chemical signals like histamine
Complement system, allergen, antigen or injury cause mast cells to release histamine
Histamine dilates capillaries, lets out more clotting elements, anti-microbial proteins
Chemokines released by capillary attract phagocytes
Clotting blocks spread of microbes

11. D) Systemic Response Widespread response Increased WBC production
Fever – facilitates phagocytosis
Septic shock – bacterial infection causes high fever low bp may cause death

12. II aquired/adaptive immunity
A) Humoral Response =
B cells make anitbodies
B) Cell Mediated Response =
Cytotoxic T cells defends against:
infected cells
Cancer cells
Transplanted cells

14. Phagocytic Cells = cells that engulf & digest antigens
Antigens =any foreign molecule recognized by a
lymphocyte (B or T cell)
a) most are proteins or polysaccharides
b) may protrude from microbe membrane
c) eptiope = tiny part the lymphocyte binds

15. MHC = major histocompatibility complex
Set of genes that code for MHC molecules
All are cell surface proteins
Class I MHC display foreign peptides synthesized within the cell (cancer/virus)
found on most body cells
Class II MHC display peptides broken off of microbes during phagocytosis
found on phagocytic cells & B cells

16. Helper–T cells
Type of T cell that binds to antigens displayed by phagocytic cells or B-cells
(Class II MHC molecules)
Helps promote aquired immune response
Promote Humoral (B-cell) response by secreting cytokines
Promote cell mediated-response (cytotoxic-T cells)

17. Antibodies Proteins secreted by differentiated B-cells (plasma cells)
Bind to specific antigen
Also called Immunoglobulins (Ig)
1) IgG – give passive immunity to fetus
2) IgA – in secretions, sweat, milk, tears
3) IgE – triggers histamines/ allergic rxns