MAPK3 and synovial sarcoma: It has been shown that IL-2 dose-dependently stimulated BAFF synthesis in PBMCs, likely through T and NK cells,38 and mediated by Erk1/2 and S6K1 signaling pathways.39 Notably, BAFF concentration in patients with SS was only slightly increased (4%) after LD-IL-2 treatment.