The identification of a VH subgroup allotypic specificity, y30, which differentiates the y33 allele into two variants. Implications for rabbit VH gene organization and evolution

Abstract

A new anti-allotype Ab, ∥ designated anti-y30, was produced by immunizing rabbits of the VH genotype a 2 x 32 y 33/ a 2 x 32 y 33 with purified IgG from a 1x −y 33 a 1x −y 33 rabbits suppressed for al Ig synthesis. Genetic analysis of 200 rabbits representing 12 heavy chain (VH-CH) haplotypes indicated that y30 was controlled by the heavy chain chromosomal region and was expressed in rabbits of the VH haplotype a 1 x − y 33 but not of theVH haplotypes a 1 x − y −, a 2 x 32 y 33 or a 3 x 32 y −. Thus, some rabbits express y33 with y30 whereas others express y33 without y30. By immunodiffusion, radioimmunoassay and sequential precipitation techniques, y30 and y33 were found to be co-expressed on most of the IgG molecules from a 1x −y 33 a 1x −y 33 rabbits suppressed for the al allotype. Also, when newborn a 1x −y − a 1x −y 33 rabbits were injected at birth with either anti-y33 or anti-y30 Ab, both allotypic specificities were initially suppressed and subsequently escaped suppression in unison. From this, we suggest that two variants of the y 33 allele exist, y 33,30 and y 33,−; an inhibition of radioprecipitation assay indicated that the y33 specificity was qualitatively similar in both variants. These allelic variants, presumably representing differences in amino acid sequence, may hve resulted from an ancestral recombinational event within a VH Cistron prior to gene duplication and expansion into present day VH subgroups. The highly restricted association observed between genetic markers of the a, x, and y VH subgroups argues against recombination between the VH subgroups.