While nIgM antibodies are secreted constitutively and play a role in preventing infection and maintaining homeostasis, large amounts of nIgM are secreted rapidly in response to microbial infection.29 Our new finding that serum nIgM is increased in CPLX2 KO mice indicates that CPLX2 has a regulatory role in the secretion of nIgM. The gene discussed is CPLX2; the disease is infection.