CXCR3 and selective IgM deficiency: Additionally, it was shown that patients with SIGMD have a decline in CXCR3 expression on both naïve and memory B cells.10 The involvement of CXCR3 in T cells and T-cell-driven autoimmunity has been extensively documented, and its contribution to B cell migration and antibody-mediated autoimmunity is gradually becoming apparent.