CCL2 and rheumatoid arthritis: In RA FLS, Sema4B alone did not modulate the mRNA expression of any of the inflammatory mediators analysed, but it enhanced the TNF-α induced expression of IL6, TNF, IL8, CCL2, MMP1 and MMP3(Fig. 5C). We validated this finding at the protein level, as Sema4B significantly enhanced the TNF-α induced secretion of TNF-α (Fig. 5D).