To determine whether T cells can recognize self-antigens presented by MHC class II molecules on autoreactive B cells, we studied 2 patients with unconventional type II bare lymphocyte syndrome (BLS), designated hereafter as patients BLS02 and BLS03, who harbored loss-of-function mutations in RFXAP and RFXANK, respectively (Supplemental Table 3). Here, RFXAP is linked to MHC class II deficiency.