CCL4 and rheumatoid arthritis: Notably, circulating levels of macrophage inflammatory protein-1β (MIP-1b/CCL4) showed suggestive inverse association with the risk of RA [odds ratio (OR): 0.95, 95% confidence interval (CI) = 0.92-0.99, p = 0.016] using the random-effects IVW method (Figure 3).