Type I natural killer T cells suppress tumors caused by p53 loss in mice.

CD1d-restricted T cells are considered to play a host protective effect in tumor immunity, yet the evidence for a role of natural killer T (NKT) cells in tumor immune surveillance has been weak and data from several tumor models has suggested that some (type II) CD1d-restricted T cells may also suppress some types of antitumor immune response. To substantiate an important role for CD1d-restricted T cells in host response to cancer, we have evaluated tumor development in p53(+/-) mice lacking either type I NKT cells (TCR Jalpha18(-/-)) or all CD1d-restricted T cells (CD1d(-/-)). Our findings support a key role for type I NKT cells in suppressing the onset of sarcomas and hematopoietic cancers caused by p53 loss but do not suggest that other CD1d-restricted T cells are critical in regulating the same tumor development.