CD4 and systemic lupus erythematosus: In addition to the B6 background, we bred Gls1 CD4-KO to the Sle1b lupus-susceptibility locus, yielding 4 groups of mice: Gls1 CD4-KO and Gls1fl/fl (“B6”) controls, and Sle1b Gls1 CD4-KO with Sle1b controls.