Although some experimental agents have been used in SLE models with favorable outcomes22,39, in the present study we did not use such agents. Instead, we administered α-GalCer, a synthetic but specific ligand of NKT cells, to investigate the role of these cells in lupus nephritis. Definitive natural ligands of NKT cells have not been so far identified. However, considering that α-GalCer is a glycolipid antigen and that some microbes may be antigenic candidates for NKT cells40,41, we think that NKT cells are involved in lupus nephritis via the glycolipid metabolism or in response to microbes.