TPH1 and systemic lupus erythematosus: Circulating Tph cells have been observed in systemic lupus erythematosus (SLE) (6, 7), Sjogren’s syndrome (8–10), IgG4-related disease (8), type 1 diabetes (11), primary biliary cirrhosis (12), immunoglobulin A nephropathy (13), juvenile idiopathic arthritis (14), autoimmune hepatitis (15), autoimmune bowel disease (16), and psoriasis vulgaris (17).