STAT1 and systemic lupus erythematosus: In SLE B cells, these changes in total STAT1 and phosphorylation of STAT3 were reflected in a reduced frequency of single IL-10-producing B cells and an increase in the expression of TNF-α and IL-6, compared to healthy controls after in vitro stimulation of PBMCs with CpGC to activate pDCs (Figures 5I and 5J).