The genetic basis for the graft-against-host reaction between inbred lines of fowls. Differences between the Reaseheath C and I inbred lines

Abstract

The splenic enlargement in chick embryos injected with adult chicken blood is the consequence of a graft-against-host reaction directed against host antigens which differ from those of the donors. The mode of genetic determination of these antigens has been studied by injecting parental line blood into F₂ and backcross chick embryos between the Reaseheath C and I lines of inbred fowls. The proportions of embryos showing no splenic enlargement have been compared with the theoretical expectations of 4^-n in the F₂ and 2^-n in the backcross to the donating line, where n is the number of antigenic loci by which the lines differ. The results suggest that the lines differ in respect of one strong antigenic locus, and possibly other weaker loci. It is believed that certain results obtained with C-line and F₁ donors may be explained by the occurrence of antigenic segregation within the C line. Evidence for a gene dosage effect was meagre. In certain donor-host combinations an enhanced splenomegaly was obtained in female embryos but the mechanism for this was not discovered.