Epistatic Suppression of Systemic Lupus Erythematosus: Fine Mapping of Sles1 to Less Than 1 Mb

Sle is a susceptibility locus for systemic autoimmunity derived from the lupus-prone NZM2410 mouse. The New Zealand White-derived suppressive modifier Sles1 was identified as a specific modifier of Sle1 and prevents the development of IgG anti-chromatin autoantibodies mediated by Sle1 on the C57BL/6 (B6) background. Fine mapping of Sles1 with truncated congenic intervals localizes it to a ∼956-kb segment of mouse chromosome 17. Sles1 completely abrogates the development of activated T and B cell populations in B6. Sle1 . Despite this suppression of the Sle1 -mediated cell surface activation phenotypes, B6. Sle1 Sles1 splenic B cells still exhibit intrinsic ERK phosphorylation. Classic genetic complementation tests using the nonautoimmmune 129/SvJ mouse suggests that this strain possesses a Sles1 allele complementary to that of New Zealand White, as evidenced by the lack of glomerulonephritis, splenomegaly, and antinuclear autoantibody production seen in (129 × B6. Sle1 Sles1 )F1s. These findings localize and characterize the suppressive properties of Sles1 and implicate 129 as a useful strain for aiding in the identification of this elusive epistatic modifier gene.