Compared with Cybb-KO controls, Tlr7 and Cybb double-KO mice had reduced splenic B cell lymphopenia, a hallmark of severe SLE in both mice and humans; this was driven by an increase in the proportion of follicular B cells (Supplemental Table 1).The proportion of splenic CD11b+CD11c+ age-associated B cell–like (ABC-like) B cells was increased in females, while the proportion of plasmablasts was unchanged. Here, CYBB is linked to systemic lupus erythematosus.