CCL2 and rheumatoid arthritis: After stimulation with 1 μg/mL ORM2 for 72 h, the levels of IL-6, CXCL8, and CCL2 produced by RA-FLSs increased 3.6-, 10.3-, and 3.4-fold, respectively, relative to those observed after treatment with medium alone (Fig. 2a).