AN ESTIMATE OF THE NUMBER OF HISTOCOMPATIBILITY LOCI IN THE RAT

Abstract
Using two inbred stains of rats of completely unrelated origins, Lewis and B.N., skin-grafts tests were performed to obtain an estimate of the number of histocompatibility loci. B.N. strain has a weak histocompatibility factor determined by a locus on the Y chromosome, but the Lewis strain does not. Large scale tests show (a) that 14 independently segregating histocompatibility genes are responsible for the incompatibility of B.N. grafts on Lewis rats, and (b) that the products of 16 genes are involved in the incompatibility of the Lewis skin on B.N. animals.