1. An antigenic substance that occurs only in some individuals of a species, such as the blood group antigens of humans. For specific isoantigens of blood group s, see the Blood Groups appendix. 2. Sometimes used as a synonym of alloantigen.
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iso·an·ti·gen·ic 'ī-(.)sō-.ant-i-'jen-ik adj
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n.
an antigenic substance that occurs only in some individuals of a species. Thus the antigens of the HLA system are isoantigens, as are the agglutinogens of the different blood group.
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iso·an·ti·gen (i″so-anґtĭ-jən) an antigen that induces an immune response when transferred (as by blood transfusion or tissue graft) to a genetically dissimilar individual of the same species.Medical dictionary. 2011.