Abnormal quantity and function of Th17 cells in patients with severe aplastic anemia combined with infection

Severe aplastic anemia (SAA) is a hematologic disease characterized by peripheral pancytopenia with bone marrow failure. Fatal bacterial or invasive fungal infections are the most frequent cause of mortality in SAA. Th17 cells are a recently discovered CD4+ T-helper subset that secrete cytokines such as interleukin 17A (IL-17A) and subsequently provide protective immunity against infections and cancer. Further, Th17 cells are also associated with chronic inflammation and autoimmunity. In this study, we analyzed alterations and quantitative and functional changes in Th17 cells in the peripheral blood of patients with SAA who had severe infections, as compared with SAA patients with recovered infection after anti-infection therapy and normal controls. The results showed that the IL-17A level in the Th17 cells of peripheral blood lymphocytes was increased in patients with SAA who had severe infections. After anti-infection therapy, the level of IL-17A in the Th17 cells was dramatically decreased. The median expression of IL-17A mRNA in the Th17 cells was increased in patients with SAA who had severe infections, as compared with the remission group and normal controls. Therefore, we concluded that an increase in excessively activated Th17 cells might participate in the immune dysfunction and the development of inflammatory response in patients with SAA who had severe infections. The above mentioned findings indicate that Th17 could be a potential target for treatment and could help improve the prognosis of SAA patients.