Rat hepatic natural killer cells (Pit cells) express mRNA and protein similar to in vitro interleukin-2 activated spleen natural killer cells

Pit cells are liver-specific natural killer (NK) cells that can be divided into high- (HD) and low-density (LD) subpopulations. The characteristics of pit cells were further investigated in this report. LD and HD pit cells ex press the specific NK-activation markers gp42, CD25, and ANK44 antigen. LD cells and IL-2-activated NK cells have a high mRNA expression of perforin, granzymes, interferon-gamma, and tumor necrosis factor-alpha. LD pit cells, unlike spleen NK cells, have a weak response to IL-2 with regard to prolif eration, cytotoxicity, and production of NK-related molecules. The characte ristics of HD cells are intermediate between LD and spleen NK cells. These results show that pit cells, especially LD cells, possess characteristics s imilar to IL-2-activated NK cells. This is the first evidence on a molecula r level that pit cells could be considered in vivo activated NK cells. (C) 2001 Academic Press.