Abstract
The spontaneous production of anti-erythrocyte autoantibodies (AEA) in New Zealand Black (NZB) mice and their hybrids has been suggested to be controlled by at least two genetic loci. A single dominant allele of NZB locus (A) determines the production of AEA, and the second locus regulates the expression of A gene. The present studies were designed to determine the nature and the location of the second locus, using NZB, C57BL/6, their F1, F2 and the F1×NZB backcrosses. The incidences of positive AEA were 100, 0, 0, 17 and 51% in these mice, respectively. This finding is in keeping with the idea that a single dominant allele of C57BL/6 locus (M) modifies (suppresses) the expression of A gene of NZB strain. M/m locus is loosely linked to Mup-1 locus on chromosome 4, and the gene order was M/m: Mup-1: Gpd-1.
We also analysed the effect of M/m locus on other autoimmune traits, and found that the gene action of M/m locus is specific for AEA production, low hematocrit and splenomegaly and is unrelated to spontaneous production of anti-DNA antibodies, anti-retroviral gp 70 antibodies and natural thymocytotoxic autoantibodies. The positive AEA was associated with the high serum IgM concentration in (C57BL/6×NZB) F1×NZB backcrosses. It was not determined whether M/m locus might also control the serum IgM concentration.
