ABSTRACT: The analysis of anti-sheep red blood cell (SRBC) antibody production in the congenic resistant (CR) mouse strains A/J and A.BY, B10 and B10.A showed that the level of IgG antibodies after immunization with SRBC is controlled by a gene(s) localized in the H-2 complex. The use of the h2, h4, and i5 H-2 recombinant haplotypes allowed us to map this gene into a region proximally defined by subregion I-J and distally by region H-2G. The IgG antibody level is simultaneously under the influence of non-H-2 genes, of which those of the A/J strain origin determine the high IgG level and those of the B10 strain origin determine the low IgG level.
Weights of spleens of the A/J and B10 mice before and after primary and secondary immunization with SRBC were compared. Before immunization, spleens of the A/J mice were approximately 10% lighter than those of the B10 mice (0.08 g vs 0.09 g). After the first immunization the spleen weights equalized (θ = 0.12 g). Four days after the second immunization the weight of the spleens of A/J mice increased by 312% (relative to the nonimmune state) while that of the B10 mice increased by only 74%. These findings indicate that the cell antigen-specific proliferation in spleens of A/J mice was considerably higher than that in spleens of B10 mice.