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Antibodies are proteins that play an
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integral role in the complex system of
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specific immunity. They bind to and
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inactivate foreign proteins called
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antigens. Each type of antibody binds to
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one kind of antigen molecule. B-cells are
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one of the two types of white blood
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cells that make antibodies. When a
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bacterial cell enters the bloodstream,
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proteins on its surface act as antigens
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and trigger a response by the immune
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system. These antigens will bind to the
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unique B cells that have the
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corresponding antibodies on their
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surfaces. These B cells now divide.
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Some continue to divide producing many
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plasma cells. Plasma cells secrete large
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quantities of antibodies into the
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bloodstream. This division of only the
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appropriate B cells is called clonal
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selection.