CCL4 and arthritic joint disease: Coincidently, a recent study of rheumatoid arthritis (RA) showed that the high responsiveness to IL-7 stimulation together with the synergy of IL-7 and M1-promoting factors (e.g., MIP-1b, TNF-a) can enhance the expression of joint myeloid IL-7R and further exacerbate arthritis (61).