Chapter40
ImmuneResponse
Our book calls theseeffector B cells
Our book callsthese effectorcytotoxic T cells
The Immune Story
1.Pathogens, either bacteria or viruses, enter the body and begin toreproduce rapidly.
2.Some pathogens are engulfed by macrophages (large phagocyticcells)
3.As it engulfs the pathogen, the macrophage removes some of thepathogen’s antigens and displays them on its own surface along withits own antigens (antigen-MHC complex)
4.Among the millions of different types of helper T cells thatdeveloped in the thymus gland and then were released, a few havereceptors that make a perfect “fit” with the antigens displayed on themacrophage membrane.
5.Helper T cells couple with the macrophage causing the macrophageto produce a chemical, interleukin-1 (IL-1). IL-1 is a pyrogen(causes fever) and activates the helper T cells to produceinterleukin-2 (IL-2)
The Immune Story (cont’d)
6.IL-2 stimulates the growth and multiplication of vast numbers of identicalhelper and cytotoxic T cells. Eventually, the cytotoxic T cells are exposedto the antigens displayed by the macrophage. Cytotoxic T cells (“killer Tcells”) chemically puncture pathogens or infected cells.
7.Helper T cells secrete other chemicals that cause B cells to multiply anddifferentiate into memory B cells and effector B cells.
8.Effector B cells produce antibodies that have binding sites that match thepathogen’s antigens. Some antibodies “stick” to pathogens, slowing themdown so they can be easily engulfed by macrophages. Some antibodiescan actually help puncture the pathogen’s membrane.
9.As the battle is won, many T and B cells die out, but the memory cellscontinue to live. These cells circulate for years to prevent a futurepathogen of the same type from ever getting started, in other words,producing immunity.
2nd Exposure to a Pathogen
