Genetic control of autoimmune disease: interactions between xid and Ipr.

A genetic experiment has been performed in mice to test the B cell "hyperactivity" hypothesis of autoantibody production. A backcross was designed such that some progeny carried both the sex-linked recessive gene xid, which markedly reduces the B cell hyperactivity and autoantibody production seen in NZB mice, and the autosomal recessive gene Ipr, which produces a severe lymphoproliferative/autoimmune disorder in the homozygous animal. The data indicate that although xid does not preclude any measured phenotypic expression of Ipr/Ipr disease, it may play a minor modulatory role. In addition, a background gene or genes in the CBA/N mouse, distinct from xid, modulates T cell proliferation in male backcross progeny. This experiment supports the view that autoimmune phenomena are fundamentally heterogeneous, and may involve complex cellular interactions.