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Regulatory T cells are vital to
orchestrating the elaborate system. (B cells, for instance, cannot make
antibody against most substances without T cell help). |
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Cytotoxic T cells, on the other
hand, directly attack body cells that are infected or malignant. |
- Most important regulatory T cell is the "helper/inducer"
cell. Helper T cells are essential for activating B cells and other
T cells as well as natural killer cells and macrophages.
- Another subset of T cells acts to turn off or "suppress"
these cells.
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- Cytotoxic T cells, are killer cells. In addition to
ridding the body of cells that have been infected by viruses or transformed
by cancer, they are responsible for the rejection of tissue and organ
grafts.
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- T cells work primarily by secreting substances known
as cytokines or, more specifically, lymphokines. Lymphokines are diverse
and potent chemical messengers. Binding to specific receptors on target
cells, lymphokines call into play many other cells and substances, including
the elements of the inflammatory response. They encourage cell growth,
promote cell activation, direct cellular traffic, destroy target cells,
and incite macrophages.
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- One of the first cytokines to be discovered was interferon
- a family of proteins with antiviral properties.
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Natural Killer (NK) cells are yet another type of
lethal lymphocyte. Unlike cytotoxic T cells, they do not need to recognize
a specific antigen before swinging into action. They target tumor
cells and protect against a wide variety of infectious microbes. In
several immunodeficiency diseases, including AIDS, natural killer
cell function is abnormal
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