In conclusion, the repeated administration of α-GalCer decreased the number of NKT cells and suppressed Th2 immune responses in these cells. This led to the suppression of B cell function and the autoimmune response, and ameliorated proteinuria and kidney pathology in experimental lupus nephritis. Therefore, we propose that NKT cells collaborate with B cells and play significant roles in the induction of lupus nephritis through their Th2 immune responses. Thus, it is important to focus on NKT cells to further investigate the precise pathogenesis of lupus nephritis.