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Cellular Immunity

Cellular Immunity - lymphocytes which bind to and destroy...

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Cellular Immunity One half of specific immunity is the activity of T-lymphocytes which attack and destroy diseased, damaged or infected host cells. After activation and proliferation , T-lymphocytes differentiate into either cytotoxic (killer) T-lymphocytes, helper T-lymphocytes, regulatory (or suppressor) T-lymphocytes, and memory T-lymphocytes. Virgin T-lymphocytes circulate in the blood or colonize the lymph nodes. T-lymphocytes have unique T-cell receptors on their surface that can recognize specific antigens. Upon activation by exposure to an antigen that matches its TCR, the virgin T-lymphocyte proliferates and differentiates. Each daughter cell is essentially a clone of the original cell; therefore, the daughter cells recognize and respond to the same antigen. This clonal selection explains the specificity of acquired immunity. The majority of mature T-lymphocytes will differentiate into cytotoxic T-
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Unformatted text preview: lymphocytes which bind to and destroy host cells that are infected by bacteria or viruses, or otherwise damaged (i.e., cancerous cell). (See Figure 5) Figure 5 Helper T-cells are essential in an efficient immune response. When activated by an APC , they secrete stimulatory chemicals that stimulate innate immunity, B-lymphocytes and other T-lymphocytes. These are the cells that are destroyed in HIV infection. (See Figure 6) Figure 6 A minority of T-lymphocytes will differentiate into memory T-lymphocytes which circulate in the blood for weeks, months, years, or decades. These cells respond aggressively and quickly to exposure to the antigen that stimulated the initial immune system response. The presence of memory cells explains the long duration of acquired immunity after exposure to an antigen....
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