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TYPES OF T CELLS - Particularly if the pathogen is a virus...

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TYPES OF T CELLS C YTOTOXIC  T  CELLS  are able to destroy target cells on contact. Intracellular pathogens cannot be  attacked by antibodies. This includes all viruses, except during the time they are free in tissues or  fluids while preparing to invade a cell, and some bacteria.   (Most bacteria cause their harm from  outside the cell, but some go inside.)  The T cell operates as follows:       1) A cytotoxic T cell specific to the antigen binds to the MHC-antigen complex on the  surface of the infected cell       2) Cytotoxic T cell releases a chemical called perforin       3) Perforin forms a pore (opening) in the plasma membrane of the target cell       4) Cell contents leak out, causing lysis and death of the infected cell       5) Cytotoxic T cells also attack some cancerous cells in the same way Remember, once a cell has been invaded by the pathogen, that cell is generally doomed. 
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Unformatted text preview: Particularly if the pathogen is a virus, it will cause the death of the cell anyway. If the cell can be destroyed before a large number of new viruses are produced inside and released, that is to our advantage. 3. D ELAYED HYPERSENSITIVITY T CELLS —these are believed to be a mixture of helper T cells and a few cytotoxic T cells that are involved with certain allergic reactions, such as poison ivy, and with the rejection of transplanted tissue. 4. S UPPRESSOR T CELLS —these are not well understood. Many immunologists believe that these cells turn off the immune response when it is no longer needed. Others think they don’t even exist, and that T H cells and T C cells change and suppress the immune response at the appropriate time....
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