IL17A and rheumatoid arthritis: The pro-inflammatory cytokine-interleukin 17 (IL-17) produced by CD4+ Th17 cells was shown to induce bone resorption in RA patients (9) and other Th17-produced cytokines (e.g., IL-6, IL-1β, IL-23, etc.)can also recruit neutrophils into synovial tissue to sustain chronic inflammation (10).