Th9 cells and IL-9 have been implicated to play pathological roles in autoimmune diseases.91 IL-9, Th9 cells and Th9 cell-associated molecular features (PU.1, IL-4, TGF-β, etc.)have been found elevated in patients with various autoimmune diseases in ulcerative colitis (UC),735 inflammatory bowel disease (IBD),736 SLE,737 RA,738 psoriasis,739 immune-related pancytopenia (IRP),740 and thrombocytopenia,741 which greatly correlates with disease severity. This evidence concerns the gene IL9 and autoimmune disease.