ITGAX and systemic lupus erythematosus: Further examination of SLE patients revealed that Double Negative B cells are a heterogenous population of cells comprised of DN1 and DN2 subsets identified based not only on CD27-IgD- but also on differential expression of CD11c and CD21, whereby DN1 cells express CD21 but not CD11c (CD21+CD11c–) and DN2 cells express high levels of CD11c in the absence of CD21 (CD21–CD11c++) (2, 9).