CD40 and autoimmune disease: In the immune system, CD40–CD40L signaling plays several key roles in regulating immune responses, CD40–CD40L signaling has been implicated in the pathogenesis of autoimmune disorders (Peters, Stunz, & Bishop, 2009) and there is increasing interest in the relevance of CD40–CD40L signaling for cancer immunotherapy (Richards, Sefrin, Gieffers, Hill, & Merz, 2019).