Similar specificity of IgG1 and IgG2a antibodies in individual mice.

In this study the previous finding of similar variable regions in individual IgG1 and IgG2a antibody populations is extended by the demonstration of similar fine specificity of IgG1 and IgG2a combining sites. Antibody populations from individual mice directed against oligo-D-alanine determinants were analyzed in their cross-reactivity towards 5 heterologous dipeptides. This was done by mixing antibody and hapten followed by determination of free antibodies in a kinetic red cells sensitization assay. The comparison of hyperimmune sera from 10 mice showed that genetically identical mice can differ significantly in their cross-reaction pattern. Within each serum the cross-reaction pattern was determined for IgG1 and IgG2a. With a few exceptions the same individual pattern was found in both IgG1 and IgG2a antibody populations. This was taken as evidence that the combining sites of IgG1 and IgG2a anti-oligo-D-alanine antibody populations in an individual mouse are similar.