Effects of leptin on Th17 cells and the possible mechanism
Objective 
To investigate the effects of leptin on Th17 cells and the possible mechanism. 
 
 
Methods 
The leptin-deficient (ob/ob) mice and their homologous wild-type mice were used in the study. The percentages of Th17 cells in peripheral blood samples, spleen tissues and lymph nodes were measured by flow cytometry (FCM) analysis. The splenic CD4+ T cells, separated from the ob/ob mice and the wild-type mice by using magnetic beads, were respectively cultured with leptin at various concentrations and with anti-leptin neutralization antibody to evaluate the effects of leptin on Th17 cells. The quantitative real-time PCR was performed to analyze Th17 cell-related cytokines at transcriptional levels. The levels of IL-6 and IL-17A in the supernatants of CD4+ T cell culture were measured with Luminex technology. 
 
 
Results 
Compared with the wild-type mice, the ob/ob mice showed lower percentages of Th17 cells in both peripheral blood samples and spleen tissues (0.49%±0.03% vs 1.29%±0.1%, 1.56%±0.22% vs 2.47%±0.11%). There was a decrease in the percentages of Th17 cells upon the in vitro treatment of CD4+ T cells from wild-type mice with anti-leptin antibody. The percentages of Th17 cells were increased in a dose-dependent manner upon the in vitro treatment of CD4+ T cells from ob/ob mice with leptin. Moreover, the levels of IL-17A and IL-6 and the transcriptional levels of RORγt, IL-17A and IL-6 in leptin deficiency group were lower than those of wild-type group, but were increased upon the treatment with leptin. No significant difference with the transcriptional levels of TGF-β and IL-23 was observed between the two groups with and without intervention. 
 
 
Conclusion 
Leptin deficiency seriously hampered the generation of Th17 cells in mice and resulted in a decreased expression of RORγt, IL-17A and IL-6 at mRNA level. The treatment of CD4 T cells with leptin might promote the generation of Th17 cells through up-regulating the transcription of RORγt and IL-6. 
 
 
Key words: 
Leptin; Th17 cell; IL-17; RORγt