CXCL8 and rheumatoid arthritis: The various pro-inflammatory cytokines (e.g., IL-1, IL-6, IL-8, TNF-α, and PGE2) and the variety of matrix metalloproteinases secreted by infiltrating macrophages in synovial fluids, which are involved in T cell activation and proliferation and mediation of cell-cell interaction, result in the release of tissue-damaging enzymes, which eventually lead to inflammation propagation and joint damage in RA (8, 43).