In rheumatoid arthritis, macrophages secrete potent cytokines and chemokines including TNF, IL-1, IL-6, IL-10, IL-12, IL18, IL-15, IL-10, GM-CSF, M-CSF and TGFβ which contribute to the chronic inflammation associated with the disease (Siouti and Andreakos 2019). Here, IL15 is linked to rheumatoid arthritis.