Immunoglobulin allotypy of allophenic rabbits.

We obtained two allophenic rabbits formed by the manipulation of blastocysts from strains which differed by their coat colour and their immunoglobulin allotypic specificities. The phenotype of these two rabbits was a1,a2,a3,b4. They were chimeras for their lymphocytic system but not for their coat colour as they had the homogeneous brown coat colour of one of their parental strain. The IgG concentration in the serum of these allophenic rabbits was of the same order of magnitude as the IgG concentration in the serum of normal rabbits of the same age. Twenty-five weeks after birth, one of the allophenic rabbits expressed predominantly the a1 allotypic specificity (around 70% a1, 5% a2, 20% a3) which came from its brown parents, while the second one expressed predominantly the a3 allotypic specificity (around 2% a1, 20% a2, 60% a3) which came from its white parents. Each allotypically different IgG produced by these allophenic rabbits possessed the whole set of allotypic determinants found on IgG carrying the same specificity and produced by normal rabbits. We did not find significant signs of genetic information transfers from the cells of one parental strain to the cells of the other parental strain, or of eventual perturbations of the functional haploidy of the immunoglobulin-producing cells. As these allophenic rabbits only had different a series allotypic specificities, the probability of finding such signs was certainly low as they would have implied hybrid IgG molecules with two allotypically different heavy chains. We now have allophenic rabbits in which different a and b series allotypic specificities are involved and with which we will look for hybrid IgG molecules with heavy chains from one parental strain and light chains from the other parental strain. With these two rabbits we observed the "chimeric drift", namely the slow disappearance of constituants (here one allotypic specificity) coming from one parental strain. The first progeny tests carried out with these allophenic rabbits indicated that they did not seem to be chimeras at the germinal cell level. All their first offspring which were homogeneously brown and homozygous a1,b4 expressed the whole set of variants and determinants of the a1 or the b4 allotypic specificity.