IL6 and rheumatoid arthritis: In their experiments in 2004, they also found that pro-inflammatory cytokines including interleukin-1 (IL-1), interleukin-6 (IL-6), TNF-α, and interferon-γ (IFN-γ) could increase the uptake of iron by monocytes and FLSs in RA patients in vitro (64).