To elucidate the mechanism by which monocytes from patients with SLE exerted this increased MAIT cell-activating capacity, we next measured concentrations of 19 cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, IL-18, IL-23, GM-CSF, granulocyte colony-stimulating factor, IFN-α, IFN-γ, and tumor necrosis factor [TNF]-α), including those known to activate MAIT cells. Here, IL4 is linked to systemic lupus erythematosus.