TNFRSF9 and systemic lupus erythematosus: While sCD137 level is increased in lupus-prone mice compared to WT mice, depletion of sCD137 prior to CD137 stimulation up-regulates the splenic production of IL-10 and IL-12 in lupus-prone mice, suggesting the regulatory role of sCD137 in counteracting an overwhelming pro-inflammatory immune response.