Antibodies (also known as immunoglobulins) are
proteins that are found in
blood or other
bodily fluids of
vertebrates, and are used by the
immune system to identify and neutralize foreign objects, such as
bacteria and
viruses. They are made of a few basic structural units called chains; each antibody has two large
heavy chains and two small
light chains. Antibodies are produced by a kind of white blood cell called a
B cell. There are several different types of antibody heavy chain, and several different kinds of antibodies, which are grouped into different
isotypes based on which heavy chain they possess. Five different antibody isotypes are known in mammals, which perform different roles, and help direct the appropriate immune response for each different type of foreign object they encounter.
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when administered, an antibody that confers short-term immunity; immune gamma globulin (IGG) provides passive protection against viral infections such as hepatitis A, measles, rubella, and varicella; immune globulin (human) (IGH) is used to prevent hepatitis B.