In (NZB x BXSB)F1 hybrid male mice, however, H2d/d developed SLE as severe as H2b/b and H2b/d backgrounds, demonstrating that the Yaa gene abrogates the MHC effect on murine lupus in (NZB x BXSB)F1 hybrid mice (27). This evidence concerns the gene HLA-C and systemic lupus erythematosus.