Two classes of 7S γ-globulins are identified in normal mouse serum and are designated 7S γ2-globulins and 7S γ1-globulins. These two immunoglobulin classes are similar in size. They differ in range of electrophoretic mobility, in specific antigenic determinants, and in genetically determined isoantigens.
Four classes of immunoglobulins in mouse serum, i.e. 7S γ2-, 7S γ1-, γ1A (ß2A), and γM-globulins, were shown to have antibody activity. Each class was characterized and shown to have distinctive immunochemical and physicochemical properties. The genetically determined isoantigens, Iga-1 and Iga-2, were shown to be present only on 7S γ2-globulin molecules.