isoantigen

n.
A protein or other substance, such as histocompatibility or red blood cell antigens, that is present in only some members of a species and therefore able to stimulate isoantibody production in other members of the same species who lack it. Also called alloantigen.

isoantigenic i'so·an'ti·gen'ic (-jĕn'ĭk) adj.
isoantigenicity i'so·an'ti·ge·nic'i·ty (-jə-nĭs'ĭ-tē) n.

An immunologically active protein or polysaccharide present in some but not all individuals in a particular species. These substances initiate the formation of antibodies when introduced into other individuals of the species that genetically lack the isoantigen. Like all antigens, they are also active in stimulating antibody production in heterologous species. The ABO, MN, and Rh blood factors in humans constitute important examples. Consequently, elaborate precautions for typing are required in blood transfusion. See also Antibody; Antigen; Blood groups.

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(ī'sō-ăn'tĭ-jən)
n.

An antigenic substance present in some members of a species and capable of stimulating antibody production in those members that lack it. Also called alloantigen.

An antigen existing in alternative (allelic) forms in a species, thus inducing an immune response when one form is transferred to members of the species who lack it; typical alloantigens are the blood group antigens.

• canine secretory a. system (CSA) — a minor histocompatibility system in dogs.