Disparate effect of beige mutation on cytotoxic function between natural killer and natural killer T cells

Beige mice lack natural killer (NK) cytotoxicity, although NK cells are nor mally present. In recent studies, NK T cells have been newly identified. We therefore examined the number and function of NK T cells in beige mice. Th e number of NK T cells was at a normal level in the liver of beige mice. NK cytotoxicity was decreased in the liver of these mice, whereas NK T cytoto xicity was intact. When immunochemical staining for perforin was conducted, the majority of NK cells and the minority of NK T cells in beige mice carr ied a giant granule, containing perforin, in the cytoplasm. In the case of control B6 mice, the majority of NK cells and the minority of NK T cells ha d multiple, dispersed granules containing perforin. These results suggest t hat NK T cytotoxicity is unaffected by the beige mutation, owing to their c ytotoxicity being mediated without the secretion system of perforin.