An immunogenetic analysis of the progeny of F1, F2, and (F1 x parental strain) test cross-matings between the CIA-susceptible DA(RT1av1) and the CIA-resistant BN(RT1n) rat strains was performed. Hybrid progeny were tested for susceptibility to CIA as induced by native calf type II collagen, and for immune response to native rat and calf type II collagens. The results show a minimum of one non-RT1-linked gene which modifies susceptibility to CIA in RT1a/a hybrid progeny. These hybrids have

more »

... ollagen immune responses equivalent to those of the parental DA strain as measured by skin testing and IgG antibody titers. An affect of sex hormones on susceptibility to CIA is indicated, because hybrid females were more susceptible than were hybrid males of equivalent RT1 allotypes.