CCL4 and rheumatoid arthritis: Moreover, elevated levels of TNF-α, Macrophage Inflammatory Protein-1 beta (MIP-1β/CCL4), IL-2, IL-6, alongside reduced levels of IL-4, IL-8, and IL1-RA, in both skin and blood compared to control groups, suggest the involvement of systemic factors in CRPS (Lenz et al. 2013; Üçeyler et al. 2007).