When Exo-FBS or Exo-RA was administered to the collagen-induced arthritis model, serum interleukin (IL)-4 and the proportion of Th2 (CD4+CD25+GATA3+) and M2 (CD11c − CD206+ of CD45+CD64+) cells were significantly increased compared to the control group. Here, IL4 is linked to rheumatoid arthritis.