Allotype and charge-related differences in the immune response.

Rabbits homozygous at the Ab kappa chain allotypic locus (Ab4/Ab4 and Ab9/Ab9) were immunized with negatively and positively charged antigens. The negatively charged antigens were bovine serum serum albumin (BSA; pI = 4.9), ovalbumin (OV; pI = 4.9) and two synthetic polypeptides: copolymer L-glutamic acid L-tyrosine (abbreviated TG; pI = 4.8) and multichain poly (L-tyrosine: L-glutamic acid) poly D-alanine: poly L-lysine (poly L-lysine backbone) abbreviated (TG) --AL; pI = 4.8). The positively charged antigen was hen egg lysozyme (LYS; pI = 10.2). Homozygous Ab9 rabbits responding to negatively charged antigens made less antibody than did Ab4 homozygotes. In contrast, both groups of animals responded equally well to positively charged lysozyme. The relative electric charges of the antibodies were assessed by Sephadex A-50 chromatography. The charge distribution was found to depend on the charge of the eliciting antigen. The positively charged antibodies of Ab9/Ab9 rabbits were not nearly as positively charged as those raised in Ab4/Ab4 rabbits. The difference in average electric charges and in the range of these charges between Ig Ab4 and Ig Ab9 explain quantitative differences in antibody formation in response to negatively charged antigens and may be a contributing factor to the "pecking order", i.e. unequal phenotypic expression of light chain genes in Ab4/Ab9 heterozygotes.