Tetraparental rabbits chimeric for their lymphoid system--I. Allotype expression.

We constructed tetraparental rabbits by immunosurgically prepared inner-cell-mass transplantation. The two constitutive parental strains were chosen so that they not only differed by their coat colour (brown and white rabbits) but also by the allotypic specificities of their immunoglobulins. It was thus possible to distinguish among the rabbits born from composite blastocysts those which were chimeric for their lymphoid system and to unambiguously quantitate the respective contribution of each parental strain to this chimerism. In this peculiar situation, the possible perturbation of the expression of immunoglobulin allotypic specificities could be tested. Thus further analysis of the tetraparental rabbit's immunoglobulins was performed to look at possible anomalies of their constitution. In only one out of the 20 tetraparental rabbits studied, we found IgG having heavy chains with the allotypic specificities of one parental strain and light chains with the allotypic specificities of the other parental strain. We did not observe, in any case, the expression of immunoglobulin allotypic specificities other than the expected ones. We always observed a marked decrease with time in the expression of the immunoglobulins produced by the lymphocytes of one parental strain accompanied by a concomitant increase in the expression of the immunoglobulins produced by the lymphocytes of the other parental strain. Two tetraparental rabbits were found to be germ-line chimeras. Analysis of the immunoglobulin allotypic specificities of the progeny of our tetraparental rabbits including these two did not reveal any perturbation in their hereditary transmission according to the usual Mendelian laws.