1. The Body’s Defense Against Disease Unleashing the Fury of the Immune System
Cytotoxic T-Cell killing a cancer cell
Macrophage engulfing bacteria

2. Non Specific Defense Mechanisms Innate Immunity
The Skin and Mucus Membrane: External Defenses are Physical barriers
Perspiration, tears and saliva contain lysozyme, an enzyme that attacks the cell wall of bacteria
Gastric Acid destroys proteins in germs by low pH
Mucus traps germs

3. Phagocytes and Natural Killers Internal Defenses
Macrophages -long living cells which develop from monocytes and engulf cells which display antigens (foreign protein patterns)
Neutrophils -short living phagocytes which usually die after engulfing a germ
Natural Killers – type of cytotoxic T-cell that identifies and destroys infected body cells by lysing membranes

4. Macrophage attacking E. coli

5. Antimicrobial Proteins Internal Defenses
a) Interferon -inhibits the production of viral proteins
Makes cancer cells less likely to metastasize
Triggers inflammatory response
Attracts macrophages
b) Complements -group of about 30 proteins which facilitate phagocytosis and lysis of infected membranes

6. 4. Inflammatory Response
a) Basophils & Mast Cells release histamine which dilate and increase the permeability of blood vessels
Increase blood supply to infected area
Causes a leakage of plasma into area
Release of leukocytosis inducing factor which stimulates the release of WBC from the bone marrow
Chemical signals also attract phagocytes
Pyrogens -increase body temperature which facilitates phagocytosis and inhibits bacterial growth

10. B. The Immune Response Active Vs Passive Immunity
Active immunity -the body is stimulated to produce its own antibodies
Passive immunity -fetus gets antibodies from mother or antibodies are injected into a patient
Duality of the Immune System
Humoral immunity -the production of antibodies which circulate as soluble protein in the blood and attack free germs
Cell Mediated immunity produces cells which attack infected cells directly

12. C. The Humoral Immune Response
B lymphocytes or B cells are activated by antigens directly or by T lymphocytes
Activated B cell begin to produce two other types of cells
Memory Cells -survive for long periods of time and proliferate rapidly when exposed to the same antigen
Plasma Cells -begin producing as many as 2000 antibodies per second for 4 to 5 days

13. 3. One Method of B Cell Activation
T independent antigen (green triangle) binds to the B cell and activates the B cell
Activated B cell divides forming memory cell and plasma cells
Plasma cells begin production of antibodies
B cell
Plasma cell
Memory cell
Antibodies

14. 4. Antibodies constitute a group of proteins called Immunoglobulins Ig

15. a) Antibody Structure
Y shaped molecule composed of 4 polypeptide chains: 2 light (small), 2 heavy chain (larger)
All four chains have regions that are constant and regions that are variable
The variable regions function as binding sites and are specific to each antigen

16. b) Types of Immunoglobulins
Ig M: Five Y-shaped monomers arranged in a pentameter. Appear in initial antigen exposure and trigger agglutination.
Ig G: Y-shaped monomer. Most abundant. Readily crosses blood vessels. Binds to antigen and activates compliment

17. Ig A: Dimer of 2 Y-shaped monomers
Ig A: Dimer of 2 Y-shaped monomers. Abundant in mucus membrane, saliva & tears
Ig D: Y-shaped monomer bound to B cells. Used as a receptor for T independent antigens
Ig E: Y-shaped monomer on basophils and mast cells. Antigen binding stimulates release of histamines

18. c) How Antibodies Work:
Neutralization -block viral and bacterial binding sites

19. 2) Agglutination -attach and immobilize germs forming clumps which are then engulfed by macrophages
Antibodies
Germ

20. 3) Activate compliment proteins which lyse cell membranes

21. 5. Activation of B Cells by Macrophages
When a macrophage engulfs a germ, partially digest antigens are displayed on its membrane
The antigens are mounted of Major Histocompatability complexes (MHC): a series of glycoproteins which allow the body to recognize self from non-self

22. c) The macrophage is now an Antigen Presenting Cell or APC and it attracts specific Helper T Cells
d) Helper T Cells bind with the APC and are activated by il-1. TH cells then release il-2 which:
Causes TH cells to reproduce and stimulates Killer T cells
Activates B Cells

23. e) B cells attach to T cells and begin to make plasma cells (which produce antibodies) and memory cells
Activated B cell
Antibodies

24. 6. T dependent and T independent Antigens
T dependent antigens -only stimulate the production of antibodies with the help of T cell
T independent Antigens -can bind directly with Ig D appearing on the B cell and stimulate the B cell without T cells

25. C. Cell Mediated Responses
T cells cannot be activated by free antigens in the body fluid
MHC -antigen complexes on APCs attract T cell. T cells bind with the complex and trigger
Activation of B cells
The production of more Helper T cells
The production of Cytotoxic T cells (T killers)

26. 3. T Helper Cells are able to stimulate other lymphocytes by sending and receiving cytokines
When T Helpers bind to APCs, the APC releases interleukin 1
This causes the T Helper to release interleukin 2 which causes T Helpers to divide and helps activate B Cells and Cytotoxic T cell

27. 4. Cytotoxic T-Cells (T-Killers) are cells which destroy cells with antigens directly
Attach to cells with antigens
Release perforin, a protein which will lyse cell membranes
This kills the cell the cell and prevents it from reproducing new viruses

28. Cytotoxic T-Cell killing a cancer cell
Perforin vessicles
Ruptured membrane
Cytotoxic T cell