You searched for: “alloantigens”
alloantigen (s) (noun), alloantigens (pl)
An antigen existing in alternative (allelic) forms in a species; therefore, inducing an immune response when one form is transferred to members of the species who lack it; typical alloantigens are the blood group antigens.
The allelic is an alternative form of a gene. One of the different forms of a gene that can exist at a single locus (spot on a chromosome). Also one of the different forms of any segment of a chromosome.