Increased percentages of T cells producing interleukin-21 in patients with immune thrombocytopenic purpura

Interleukin (IL)-21, a cytokine which promotes differentiation of Th17, follicular helper T cell and B cells, may play an important role in controlling the autoimmune process in immune thrombocytopenic purpura (ITP), an acquired organ-specific autoimmune hemorrhagic disease. The frequencies of IL-21-producing T cells and serum levels of IL-21 were determined by flow cytometry analysis and ELISA, respectively, in 24 ITP patients and nine healthy controls. RT-PCR showed that the frequencies of circulating IL-21-producing T cells and serum levels of IL-21 were significantly higher in ITP patients than that in healthy controls. Serum IL-21 and IL-21 expression in patients with ITP significantly decreased after therapy, suggesting IL-21 might be important in ITP.