Antigenic determinants that differ among individuals of the same species, such as the epitopes of the Rh blood group system or epitopes of the HLA system.

Antigenic determinants that are present in allelic (alternate) forms. When used in association with immunoglobulin, allotypes describe allelic variants of immunoglobulins detected by antibodies raised between members of the same species.

Genetically determined variants of antibodies.

Small or concealed variations of a type.