hiv is deadly because it destroys the immune system

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Unformatted text preview: molecule that elicits a response from a lymphocyte is called an an.gen. ! Ager binding to an anDgen, a B cell can give rise to short- lived cells that secrete receptor- like molecules that circulate in the blood and lymph. Such a secreted molecule is called an an.body and is specific for that same anDgen. ! At first, an anDgen acDvates only a Dny number of lymphocytes with receptors specific to that anDgen. These “selected” cells then proliferate, forming a clone of cells (a populaDon of geneDcally idenDcal B cells or T cells) that are specific for the sDmulaDng anDgen—clonal selec.on. ! Short- lived cells that have an immediate effect against the anDgen that triggered their producDon are called effector cells. ! The first response to exposure of lymphocytes to an anDgen, called the primary immune response, takes several days to produce effector cells via clonal selecDon. ! Memory cells are long- lived cells that respond to subsequent exposures to the anDgen by giving rise to effector cells and also more memory cells. ! Memory cells can last in the body for decades. When the anDgen is encountered again, the memory cells that bind to it iniDate a faster and stronger response called the secondary immune response. ! Immunity is usually acquired by natural infecDon, but it can also be achieved by vaccina.on. In this procedure, the immune system is confronted with a vaccine composed of a harmless variant of a disease- causing microbe or one of its parts. ! The vaccine sDmulates the immune system to mount defenses against these anDgens. ! The secreDon of anDbodies into the blood and lymph by effector B cells is called the humoral immune response. ! This response, the humoral immune response, defends primarily against bacteria and viruses in body fluids. ! Cell- mediated immune response involves two main types of effector T cells: helper T cells and cytotoxic T cells. ! Helper T cells bind to other white blood cells that have previously encountered an anDgen. ! An acDvated helper T cell responds in several ways. It grows and divides, producing more acDvated helper T cells, as well as memory T cells. In addiDon, it sDmulates the acDvity of cytotoxic T cells and helps acDvate B cells, thus engaging the humoral response as well. ! Cytotoxic T cells are the only T cells that can actually kill other body cells. They idenDfy infected body cells in the same way that helper T cells idenDfy their targets:...
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This document was uploaded on 03/02/2014 for the course BIO 101 at University of Tennessee.

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