Genetics of restricted antibodies to streptococcal group polysaccharides in mice II. The Ir‐A‐CHO gene determines antibody levels, and regulatory genes influence the restriction of the response

The immune response of mice to the cell wall polysaccharide of group A streptococci is controlled by a single, autosomal gene, the Ir‐A‐CHO. Ir‐A‐CHO appears to occur in the form of three alleles: allele a determines high responsiveness; it is dominant over allele b, which confers low responsiveness. The combination of allele a with a proposed second low responder allele c leads to intermediate immune responses. Ir‐A‐CHO is not linked to the locus that controls hair color, the agouti‐locus, nor is it linked to the CH allotype or the H‐2 complex. In addition to Ir‐A‐CHO the immune response to the streptococcal group A polysaccharide is controled by genes which determine the heterogeneity of the response. This complex but nevertheless limited set of genes is autosomal, codominant and generally has no specificity with respect to the expression of a certain set of variable region genes of antibodies. These traits must be regarded as regulatory genes whose control is independent of the CH allotype.