IL9 and systemic lupus erythematosus: Further analysis showed that the percentage of Th9 cells was significantly correlated with the disease activity index of SLE, and the level of serum IL-9 decreased obviously after treatment with glucocorticoid or methylprednisolone, suggesting that Th9 cells were not only involved in the occurrence of SLE, but could also be used as an important index of clinical efficacy.