Humorial & Cell-related immunity defend against different types of threats.

1. Humorial & Cell-related immunity defend against different types of threats. ^Is this even English!?^ book chapter 43.3… mostly.

2. To understand what the heck we’re talking about, you need some background. • Early immunization theory: • When early scientists transferred fluids like plasma and lymph (archaic term: “Humors”, therefore “humoral” in the first slide) from one animal to another, the second animal gained an immunity to microbes the first animal had been exposed to. • They found that certain immunities could only exist if T-cellswere also transferred.

3. But what does that mean? • Therefore, there are two kinds of immunity: • Humoral immune response refers to the activation of B cells to produce Antibodies that are circulated in the blood and lymph systems. • Defends against pathogens and toxins in extracellular fluid. • Cell-mediated immune response activates cytotoxic T cells, which directly attack and destroy target cells. • Defends against infected cells, cancer cells, and transplanted tissues. • The whole process is initiated by Helper T cells, which identify the antigen and stimulate the two immune responses accordingly. • HTCs use a surface protein called CD4 to bind to Class II MHC sites on antigen-presenting cells in order to identify the antigen. • Once the antigen is identified, the HTC activates either the B Cells or the cytotoxic T cells. http://www.youtube.com/watch?v=aSpRpf1Ny9A

4. More than you ever wanted to know about Cytotoxic T Cells… Cytotoxic T Cells target MISBEHAVING cells. They bind to class I MHC molecules using CD8. Recall: Class II MHC/CD4 and Helper T Cells. They destroy infected and/or cancerous cells, which it identifies because tumor cells carry antigens not normally found on body cells. Certain cancers and viruses such as Epstein-Barr (Mono) reduce the class I MHC sites on the cell, rendering CTCs less effective. Natural Killer cells can take care of these no problem, though.

5. …And about B Cells When a B cell encounters a specific antigen, it triggers a humoral response. Usually this is just to bacteria or incompatible transplanted tissues/transfused blood. In some people, however, pollen, bee venom, etc can induce a hypersensitive reaction. This is an allergy. Helper T cells secrete cytokines that differentiate the B cell into clone groups, one of antibody-secreting plasma cells, and one of memory B cells. B cells are specifically effective against the one antigen they can bind to. Each separate antigen results in a different cadre of B cells. Some antigens only trigger an immune response in the presence of Helper T cells. They are T-Dependent Antigents. Other antigens, like bacterial capsules and flagella trigger antibodies without Helpter T cells. They are T-Independent antigens.

6. IB Wants us to talk to you about HIV/AIDS. • HIV (Human Immunodeficiency Virus) works by attacking Helper T Cells. • This leads to a reduction of the number of active lymphocytes and a loss of the ability to produce antibodies. • The effects of HIV as defined by the IB syllabus is limited specifically to the above. • AIDS (Acquired Immune Deficiency Syndrome) is defined by the presence of one or more opportunistic infections (ie, Kaposi's Sarcoma) due to advanced HIV infection. • HIV is transmitted via exchange of bodily fluid via sexual contact, intravenous drug use, from mother to child, or transplant and/or transfusion of infected organs and blood.

7. CLASS DISCUSSION TIME! • IB wants us to connect to TOK here. • From the syllabus: • 6.3.8 Discuss the cause, transmission and social implications of AIDS. • Aim 8: The social implications of AIDS are well known. Cases of AIDS are not evenly distributed in the world, and consideration could be given to the severe problems in southern Africa. Cultural and economic reasons for differences in the prevalence of AIDS could be considered. The moral obligation of those with the technology and the wealth to help others lacking these things could be discussed. • TOK: The different methods of transmission of HIV each carry their own risk. The extent to which individuals in different societies can minimize or eliminate each of these risks could be considered.

8. Monoclonal antibodies & diagnosis • B Cells fuse to tumors and other antigens, resulting in a proliferation of antibodies. • Detection of these antibodies is indicative of exposure to the antigen. • Presence of HIV antibodies is use to diagnose an HIV infection. • Drugs can be attached to monoclonal antibodies to treat certain cancers.

9. Types of immunity as defined by antibodies. • Active: Immunity due to exposure to antigens and production of antibodies. • IE: You had chicken pox as a child, and now you are immune. • Vaccination is also considered to be “active” immunity. • Passive: Immunity due to acquisition of antibodies from another source. • IE: Across the placenta, via Colustrum (mother’s milk), and through injection of antibodies. • Passive immunity is temporary but allows the body time to develop active immunity without falling under undefended attack.

10. Can you….? • Define ‘Pathogens’? • Explain why antibiotics work on bacteria but not viruses? • Distinguish between antibodiesand antigens? • Explain antibody production? • Outline the effects of HIV on the immune system? • Explain the production of monoclonal antibodies and give one example of diagnosis and one treatment? • Explain the difference between active and passive immunity?