Recombinant Rabbit Secretory Immunoglobulin Molecules: Alpha Chains with Maternal (Paternal) Variable-Region Allotypes and Paternal (Maternal) Constant-Region Allotypes

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Abstract
A population of IgA molecules having heavy chains coded by two parental chromosomes in trans position has been identified in rabbits heterozygous at both the V H a locus, which controls allotypic specificities on the variable part of heavy chains, and the C α g locus, which controls allotypic specificities on the constant part of alpha chains. These recombinant molecules have alpha-chain allotypic specificities controlled by both the maternal V H a gene and the paternal C α g gene or conversely, the paternal V H a gene and the maternal C α g gene. These recombinant molecules were found in F(ab) 2α fractions obtained after passage of F(ab) 2α preparations through immunosorbent columns designed to remove one population of F(ab) 2α molecules, i.e., g74- or g75-type molecules. The effluent F(ab) 2α fractions were then examined by radioprecipitation methods for allotypic specificities controlled by the V H a and C α g loci. About 40% of the g75 F(ab) 2α molecules from each of three rabbits with the a 1 g 74 and a 2 g 75 allogroups were alg75 recombinants. These alg75 recombinant molecules represented from 2.5-5.6% of the total unfractionated F(ab) 2α sample. The F(ab) 2α fractions from two rabbits with the a 1 g 75 and a 3 g 74 allogroups had from 1.8-8.2% recombinant molecules: some were alg74 recombinants and some were a3g75 recombinants. Somatic recombination as a mechanism responsible for the synthesis of polypeptide chains in which part of the information is obtained from one chromosome and part from the homologous chromosome is discussed.