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Unformatted text preview: T CELLS AND CELL-MEDIATED IMMUNITY This is based on the activity of certain specialized T cells. This type of immunity is not transferred across the placenta, and occurs mostly in response to intracellular pathogens. T cells (T lymphocytes) are the key to cell-mediated immunity. They develop in the bone marrow, but leave it while still in an immature form and migrate to the thymus gland. There, influenced by thymic hormones, they reach maturity. They then migrate to lymphoid organs of the body. Like B cells, each T cell is programmed to respond only to one certain antigen because it has antigen receptors on its surface only for that particular antigen. When activated by contact with its antigen, the T cell also proliferates and differentiates. This is also known as clonal selection. Also like B cells, some of the activated T cells become memory cells, able to respond quickly to...
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- Fall '09
- cells, Bone marrow