Coincidence of autoantibody production with the activation of natural killer T cells in α-galactosylceramide-mediated hepatic injury.

Natural killer T (NKT) cells are known to be specifically activated by α-galactosylceramide (α-GalCer) via their interaction with CD1d. At that time, NKT cells mediate autoreactivity and eventually induce hepatic injury. As these immune responses resemble acute autoimmune hepatitis, it was examined whether autoantibody production and the activation of autoantibody-producing B-1 cells were accompanied by this phenomenon. Autoantibodies against Hep-2 cells and double-stranded DNA were detected in sera as early as day 3 (showing a peak at day 14) when mice were treated with α-GalCer. On day 3, B220(low) cells appeared in the liver. These B220(low) cells were CD5(-) (i.e. B-1b cells) and CD69(+) (an activation marker). Primarily, such B220(low) cells were present in the peritoneal cavity, but the proportion of B220(low) cells increased with the administration of α-GalCer even at this site. In parallel with the appearance of B220(low) cells in the liver, hepatic lymphocytes acquired the potential to produce autoantibodies in in vitro cell culture in the presence of lipopolysaccharide. These results suggested that hepatic injury induced by α-GalCer administration resembled acute autoimmune hepatitis and that the major effector lymphocytes were NKT cells with autoreactivity and autoantibody-producing B-1 cells.