Immunoglobulins of the marsupial Setonix brachyurus (Quokka). Characterization of three major serum classes, IgG2, IgG1 and IgM.

Three immunoglobulin classes, IgG2, IgG1 and IgM, have been identified in the serum of the marsupial (quokka). Each of these classes has been isolated in pure form and partially characterized physicochemically. These immunoglobulins differed in their electrophoretic mobility, molecular size, carbohydrate content and in the antigenic determinants of their heavy chains. IgG2 exists in two major subclasses, one of which (IgG2a) was isolated as a homogeneous preparation. The results of immunoelectrophoretic analyses also suggest the likely presence of subclasses within the IgG1 class. This molecular complexity of the quokka humoral immune system is much greater than that of birds and ectotherms, but is comparable to that shown by eutherian mammals.