Clonotypes of anti-phosphocholine antibodies induced with Proteus morganii (Potter). II. Heterogeneity, class, and idiotypic analyses of the repertoires in BALB/c and A/HeJ mice.

The heterogeneity of the PC-specific IgG response of Proteus morganii (Potter) was systematically analyzed. Serum samples from individual mice were focused in paired adjacent tracks, PC-specific antibodies were detected with 125I-PC-RNase, and the resulting autoradiographs were examined for co-focusing bands. Both the number of different antibody band groups and their frequency of expression were determined. Varying qualitatively from simple to complex, the spectrotypes of 38 BALB/c and 19 A/HeJ each appeared unique. However, after thorough analysis for co-focusing bands. It was evident that each spectrotype reflected a unique combination of shared band groups rather than numerous uniquely focusing band groups. The responses of A/HeJ and BALB/c showed striking similarities qualitatively in the appearance of individual spectrotypes. The heterogeneity of the two strains was also similar quantitatively. The basis for this finite though complex heterogeneity was examined by in situ subclass analysis after IEF and idiotype analysis of IEF bands by using antibodies purified from individual BALB/c and A/HeJ. Each mouse primarily expressed IgG3, and antibody bands of this subclass ranged from pI of 6.75 to 8.2. IgG1-positive bands ranged from pI of 6 to 7. Minimal amounts of IgG2 and IgM were detected. In comparisons of individual mice, there was more heterogeneity apparent in the IgG3 subclass than in the IgG1. The idiotype, IdX-M603, was found in both subclasses and also in multiple band groups focusing at different positions within each subgroup. Possible explanations for this heterogeneity among these idiotypically related antibodies are discussed.