1. Human Anatomy and Physiology Immunology: Adaptive defenses

2. Overview System must be primed before it can take effect 1800 experiment Inject a bacteria into an animal It raises proteins (antibodies against the infection Serum containing antibodies protects other animals not previously exposed

3. Overview Characteristics of adaptive response Specific recognition of pathogens Response is systemic Response has memory (mounts a stronger attack on subsequent exposure) Injecting lymphocytes also offered protection

4. Types of immunity 1. Humoral Antibodies produced from lymphocytes present in body as ‘humor’ 2. Cellular Lymphocytes themselves defend the body

5. Antigens Substances provoking an immune response (i.e. any foreign cell) Not normally present in body, therefore ‘nonself’ Self recognition Major histocompatibility complex (MHC) class I proteins - all cells except RBCs MHC class II proteins (on APC cells)

6. Humoral immunity

7. Clonal selection- Steps B-cells clone themselves upon encountering an antigen (1° response, 3 - 6 days) Resulting plasma cells secrete antibodies into plasma Clone cells not differentiating into plasma cells become memory cells Re-infection produces a 2° response

8. B-cell cloning

9. Humoral responses

10. Antibody structure Immunoglobulins (Ig) 4 polypeptides 2H, 2 L (disulphide bonds) Antibody monomer, T or Y shaped 2 antigen binding sites C (constant) region V (variable) region

11. Antibody classes Classification based on C region in heavy chain IgD, IgG, IgE, IgA, and IgM pentamer dimer monomer

12. Antibody functions Antibodies inactivate antigens and tag them for destruction Strategies Neutralization Agglutination Precipitation Complement

13. Humoral immunity Active - natural vs. artificially acquisition, memory B cells Long term protection Passive - not challenged by antigens, no memory B cells Short term protection. From mother several months, gamma globulin (gG) weeks.

14. Cells of adaptive immunity 1. Lymphocytes (B cells, T cells) T cells (immunocompetent in thymus) B cells (immunocompetent in bone marrow)

15. Cells of adaptive immunity 2. Antigen-presenting cells (APC) Engulf antigens, present fragments to T c -cells to destroy e.g. CT - dendritic cells, skin - Langerhans’ cells, lymph - macrophages

16. Cell-mediated immunity 2 types of T-cells, CD4 (T H ) and CD8 (T C ) T-cells activate by double recognition V region binds to an antigen, also recognize self (MHC class I proteins)

17. Cell-mediated immunity Helper T Cells Bind to APC and help stimulate T cell and B cell proliferation using interleukin-2 (hormone)

18. Clinical connections 1. Organ transplants Tissue similarity so that Tc cells, NK cells and antibodies do not attack the new organ Immunosuppressive therapy Anti-inflammatory drugs Immunosuppressant drugs 2. Immunodeficiencies Immune cells, phagocytes, complement behave abnormally AIDS/HIV - helper T cells destroyed

19. Clinical connections 3. Autoimmune diseases - loss of ability to distinguish self from non-self. Body produces antibodies against its own cells MS: destroys white matter of brain and spinal cord Type-1 diabetes: destroys pancreatic ß cells 4. Allergies Anaphylaxis: basophils and mast cells become oversensitized to allergens, resulting in histamine release causing inflammation Anaphylactic shock