Immune Memory and Vaccines B-cell activation and Memory B-cells Acquired Immunity –“natural” after infection or disease –“artificial” through vaccine Vaccines

When B-cells activate…

B-cell clones Of B-cells in body (remember that each has a gene combination for a specific antibody), most will never encounter an antigen that their antibody or BCR “recognize” or that causes them to activate For those who do, they begin undergoing mitosis, forming clones or cells that have the exact same antibody (or BCR) gene combination The clone cells become either: –Plasma cells that make antibodies or immunoglobulins that are released into the blood stream –Memory B-cells…

Have BCR that recognizes antigen that caused original “mother cell” activation Thousands (millions?) are made so body is ready for next exposure to that antigen Thus, secondary response (when body is again exposed to same antigen) is much faster than primary response Memory B-cells

Memory T-cells Virtually same process happens with T-cells

Acquired Immunity Presence of Memory B-cells and Memory T-cells provides acquired immunity to the disease- causing microbe that originally introduced the antigens that caused the “mother cells” to activate. Two ways to acquire this kind of active immunity* (active because the body actively produces antibodies to trigger a quick secondary response) –Naturally acquired active immunity: example— common cold viruses –“Artificially” acquired active immunity: Vaccines… *Passive immunity: Antibodies come from outside source—body does not produce them from activated B-cells. Source can be “natural (from mother’s blood across placenta in fetus or mother’s milk during nursing in infant) or “artificial” as in antibody injections, frequently used against venoms (“antivenom) or for temporary immune protection (“antiserum” made of antibodies harvested from cell cultures of cells with antibody that respond to antigen associated with disease-causing agent)

What is vaccine? Edward Jenner and small pox vaccine (1796) Vaccines can come from: –Similar disease (cow pox/small pox) –Living, “attenuated” virus (polio) –Dead virus (most vaccines) –Antigens from disease-causing organism— usually case with bacterial vaccines

How do vaccines work? (and why do they work with some diseases and not others?) Disease-causing organism must have antigens that immune system can “see” Disease-causing organism must not mutate too rapidly (AIDS) or have too many different strains or causative-agents (common cold) “Herd” vaccination is probably more important than individual protection Flu vaccine example:

Vaccine Development and Production