1. Adaptive Immunity Substances recognized as foreign that provoke an immune response are called antigens (Ag). Adaptive immunity describes the ability of the body to adapt defenses against the antigens of specific bacteria, viruses, foreign tissues… even toxins (think of the snake handler who becomes immune to the venom of snake bites).

2. Adaptive Immunity Two properties distinguish between adaptive immunity and innate immunity: 1.Specificity for foreign molecules which act as Ag this involves distinguishing self-molecules (normal, not antigenic) from nonself molecules 2.Memory forpreviously encountered Ag

3. Not all foreign substances are antigenic: We don’t make antibodies to glass, for example. Molecules, or parts of molecules tend to be antigenic if they are: Foreign – not ourselves Organic Structurally complex (proteins are usually complex and form many of the most potent antigens) Large (high molecular weight) Adaptive Immunity

4. Antigens can have multiple antigenic determinants called epitopes. Each epitope is capable of producing an immune response. Entire microbes may act as an antigen, but typically just certain small parts (epitopes) of a large antigen complex triggers a response. Antigens can have multiple antigenic determinants called epitopes. Each epitope is capable of producing an immune response. Adaptive Immunity

5. The adaptive immune response cannot get started without the aid of the nonspecific phagocytosis that occurs in the innate immune response. The phagocytic cells that initiate the process are called antigen presenting cells.

6. Antigen-presenting cells (APCs) are mostly dendritic cells and macrophages, and they link the innate immune system and the adaptive immune system. – Dendritic cells are usually found in tissues in contact with the external environment, and they are the most potent of the antigen-presenting cell types. Dendritic cells grow branched projections called dendrites that give the cell its name. However, these do not have any special relation with neurons which possess similar appendages Adaptive Immunity

7. As an antigen-presenting cell engulfs and destroys a foreign invader, it isolates the antigens those cells “display”. The APC then presents the foreign Ag to a specific T lymphocyte called a helper T cell (also known as a CD4 cell). Processed Ag is presented

8. Adaptive Immunity Once stimulated by antigen presentation, helper T cells become activated. Activated helper T cells are capable of activating other lymphocytes to become T cytotoxic cells (CD8 cells) which directly kill foreign invaders and B cells (which make antibodies that kill or helps kill foreign invaders).

9. Adaptive Immunity Activated B and T cells form the two arms of the adaptive immune response: Antibody-mediated immunity and Cell-mediated immunity. Helper T cells aid in both types, and both types work together to form specific bodily defenses. The Innate and Adaptive Immune systems are depicted

10. Adaptive Immunity Cell-mediated immunity involves the production of cytotoxic T cells that directly attack invading pathogens (foreign invaders with Ag harmful to us – particularly intracellular pathogens and some cancer cells). Suppressor and memory T cells are also produced. Antibody-mediated immunity involves the production of B cells that transform into antibody making plasma cells. Antibodies (Ab) circulate in extracellular fluids. B memory cells are also produced.

11. Adaptive Immunity B-cells can be activated by direct recognition of antigen through B-cell receptors or through T-helper cell activation. Activated B-cells undergo clonal selection to become antibody producing plasma cells.

12. Adaptive Immunity