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.
