Role and strain distribution of genes controlling light chains needed for the expression of an intrastrain cross-reactive idiotype.

Several strains of mice were tested for their capacity to provide immunoglobulin L chains required for the expression of the major cross-reactive idiotype (CRIA) associated with p-azophenylarsonate-specific antibodies of strain A mice. To facilitate testing, mice were bred that were homozygous for Igh-Ce and Lyt-2a, 3a, i.e., they possessed genes controlling H chains but not L chains required for expression of the CRIA. Such male mice were mated to females of various strains and their offspring were tested; expression of CRIA indicated the presence in the female parent of genes controlling the appropriate L chains. All females bearing the Lyt-2a, 3b or Lyt-2b, 3b genotype yielded offspring, most of which were CRIA+, whereas all the offspring of females that were Lyt-2a, 3a were CRIA-. The female parents included mice of several strains that are congenic for Lyt-2a, 3a, Lyt-2b, 3b or Lyt-2a, 3b, thus demonstrating very close linkage between the Lyt loci and the expression of CRIA. In addition, doubly congenic strains of mice with the heavy chain allotype of the CRIA+ AL/N strain and the Lyt-2a, 3a genotype on a BALB/c background failed to express CRIA. The data provide further evidence for the similarity of repertoires of L chains in Lyt-3b mice of various strains. When genes were present controlling A/J H chains and L chains of C57BL/6 or BALB/c origin, the quantitative expression of CRIA was only slightly lower than that observed in A/J mice. Mice possessing genes controlling the H or L chains required for CRIA expression, but not both, did not express CRIA but synthesized Ar-specific antibodies which contained low but significant concentrations of the idiotype-associated chain.