Upregulated IL-21 and IL-21 receptor expression is involved in experimental autoimmune uveitis (EAU)

PURPOSE Interleukin (IL)-21 has recently been shown to play a vital role in the development of many autoimmune diseases. Our study is designed to investigate the alteration and possible function of IL-21 in the development of an experimental autoimmune uveitis (EAU) model. METHODS EAU was induced in B10.RIII mice by subcutaneous injection of interphotoreceptor retinoid-binding protein (IRBP) 161-180 emulsified with complete Freund's adjuvant (CFA) and evaluated by clinical and histopathologic observation. IL-21 and IL-21R mRNA expressions in cells of draining lymph node (DLN) and spleen in EAU and control mice were determined by reverse transcription-PCR. The frequencies of interleukin-21 receptor positive cells were also examined using flow cytometry. IL-17 levels in the supernatant of the cell culture upon IL-21 stimulation were assayed by enzyme-linked immunosorbent assay. RESULTS Results showed that EAU was successfully induced by IRBP161-180. Expression of IL-21 mRNA was significantly increased in cells of DLN and spleen in EAU compared with recovery phase mice and normal controls. IL-21R was also found upregulated in DLN and spleen cells of EAU mice by reverse transcription-PCR and flow cytometry. Cells in EAU cultured with IL-21 combined with transforming growth factor-beta induced increased production of IL-17. CONCLUSION The findings revealed that increased IL-21 and IL-21R expression may be involved in the development of EAU, possibly by promoting IL-17 secretion.