[Anti-RaRBC antibodies in human serum. II. Presence of incomplete anti-RaRBC antibodies in the serum of healthy persons].

Non-agglutinating character of some anti-rabbit erythrocytes (RaRBC) antibodies was demonstrated. Non-agglutinating ("incomplete") antibodies were identified mainly as IgG but in some sera were detected also in IgA and IgD class using indirect Coombs test with monospecific antisera. Neutralization and separation of "complete" (IgM) antibodies were performed using 2-mercaptoethanol treatment and/or preparative immunochemical techniques. Some kind of restriction to kappa light chains and to IgG2 subclass has also been observed but monoclonal character of "incomplete" antibody was excluded. Specificity of reaction of IgG anti-RaRBC antibodies with RaRBC membrane antigens was documented using multiple adsorption-identification experiments. Non-specific (Fc-mediated) reaction was excluded in contrast to previously published results on the presence of Fc receptor on RaRBC.