MASP2 gene deficient (MASP2‐/‐) mice treated with bovine collagen type II protected arthritis induction, evidenced by reduced clinical disease activity, decreased histopathological scores, C3 deposition and infiltration of synovial macrophages, neutrophils, whereas the wild‐type mice showed severe features of arthritis.18 The gene discussed is C3; the disease is Arthritis.