hIgD-Fc-Ig fusion protein regulates T cell functions by inhibiting TCR signaling pathway in adjuvant arthritis rats

This study aimed to investigate the effect of hIgD-Fc-Ig on TCR-Lck-Erk activated by IgD in adjuvant arthritis (AA) rats. Wistar rats were divided into the normal, AA model, hIgD-Fc-Ig (1 mg/kg, 3 mg/kg and 9 mg/kg) and Etanercept (3 mg/kg) groups. The overall index of AA rats was measured every 3 days. The pathologic examination of knee joints and the proliferation of the spleen and thymus of AA rats were detected by H&E staining and CCK-8. The blood flow signal of knee joints of experimental rats was examined by US. The articular bone injury was detected by X-ray. The changes in PBMCs and spleen T cell subsets were detected by flow cytometry. The expression of CD3ε, p-Lck, p-Zap70, Ras, and p-Erk in rat spleens was detected by immunofluorescence and WB. Rat spleen T cells or Jurkat cells treated by IgD to observe the effect of hIgD-Fc-Ig on TCR and its downstream protein expression. The results showed that hIgD-Fc-Ig had a therapeutic effect on AA rats by reducing the secondary inflammation, improving pathological changes. hIgD-Fc-Ig can reduce the ratio of Th cells of PBMCs of AA rats, the ratio of Th, Th1, Th17 cells and increase the ratio of Th2, Treg cells of AA rat spleens. hIgD-Fc-Ig could down-regulate the expression of CD3ε, p-Lck, p-Zap70, Ras, p-Erk in vivo or in vitro. In conclusion, hIgD-Fc-Ig could alleviate the symptoms of AA rats and regulate T cells through TCR-Lck-Erk signaling pathway and maybe a new promising biological agent for RA.