CD40LG and systemic lupus erythematosus: Furthermore, although NZB chromosome 1 is reported to contain a genetic locus that facilitates anti-RBC Ab production in crosses with other lupus susceptibility loci [9], anti-RBC Abs were not produced in either B6.NZBc1 or B6.NZBc1c13 mice (%RBC IgM+, B6 = 1.39%±0.95 n = 4; B6.NZBc1 = 2.10%±0.87, n = 7; B6.NZBc1c13 = 2.23%±0.92, n = 8; all p>0.05 as compared to B6: %RBC IgG+, B6 = 0.67%±0.29, n = 4; B6.NZBc1 = 0.73%±0.46, n = 7; B6.NZBc1c13 = 0.77%±0.26, n = 8; all p>0.05 as compared to B6).