Are “hidden” genes for immunoglobulin allotypes of rabbit heavy and light chains expressed upon hyper‐immunization?

Abstract

AbstractThe question of whether genes for some Ig‐allotypic forms may be “hidden” in the genome was investigated by hyperimmunization of 36 allotypically pedigreed rabbits with a vaccine of Micrococcus luteus (Micrococcus lysodeikticus). Since Strosberg et al. (J. Immunol 1974.113: 1313) have reported that such hyperimmunization elicited expression of a third “allele” at two different loci (a2 and b6 in a rabbit whose original phenotype was ala3b4b5), we wished to determine whether their immunization protocol would reproducibly elicit expression of “hidden” allotypes. None of the 36 immunized rabbits developed elevated expression of an unexpected allotype during the 7‐38 weeks of immunization and bleeding. However, we did observe elevated expression of unusual variable regions. In particular, a cross‐reaction between some VH region gene products produced by al rabbits, and the majority of VH products of a2 rabbits was detected with anti‐a2 antisera made in a3a3 but not in a1a1 or a1a3 rabbits. There is a small percentage of Ig molecules in a1a1 rabbits whose V regions contain an antigenic determinant also present on most or all a2 molecules of rabbits. A similar determinant is also found on Ig of related genera (Lepus and Sylvilagus) Expression of this population was elevated during immunization of an a1a3 rabbit with Micrococcus. In immunodiffusion, a reaction of partial identity was observed. In hemagglutination inhibition, the reaction of a3 anti‐a2 with homologous a2 was not inhibitable by the cross‐reacting component. Anti‐a2 antisera made in a3 rabbits could be depleted of cross‐reactive antibody by absorption with insolubilized sera from normal al rabbits but not by insolubilized a3 sera. Radioautography of isoelectric focusing plates overlayed with a3 anti‐a2 antibodies which had been affinity‐purified and radiolabeled, revealed distinct spectrotypes in sera from al rabbits that carried the cross‐reacting VH determinants.