IMMUNOGLOBULIN

n. antibody, any of several blood proteins which identify and disable infectious foreign bodies; part of the blood serum that contains antibodies (Immunology)

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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Immunoglobulin /im·mu·no·glob·u·lin/ a protein of animal origin with known antibody activity, synthesized by lymphocytes and plasma cells and found [more]Immunoglobulin - Community and Resources

Noun
1. a class of proteins produced in lymph tissue in vertebrates and that function as antibodies in the immune response
(synonym) Ig, immune serum globulin, immune gamma globulin, immune globulin
(hypernym) gamma globulin, human gamma globulin
(hyponym) immunoglobulin A, IgA

A protein that acts as an antibody.