FCRL3 and myeloid sarcoma: Given the integral involvement of B cells in MS progression and their close association with FCRL3 (19), TLR9 activation affects B cell proliferation, apoptosis, antibody production, and IL-10 secretion by upregulating FCRL3 expression, FCRL3 can activate the SHP-1 and p38 MAPK pathways and then promote the secretion of IL-10 in B cells, thus inhibiting the secretion of inflammatory factors (19, 20).