Augmentation of natural killer cell activity by anti-host delayed-type hypersensitivity during the graft-versus-host reaction in mice.

During a graft-versus-host (GVH) reaction in unirradiated F1 hybrid mice there is a generalized activation of natural killer (NK) cells. We have examined whether the enhanced NK activity is due to an F1 resistance mechanism directed at the parental cells used to induce the GVH reaction. Spleen cells of C57BL/10 origin induce much more NK cell activation in B10F1 hybrids than the opposite parental type, despite a similar intensity of systemic GVH reactions. However, this does not correlate with in vivo resistance of mice with GVH reaction to a local challenge dose of B10 cells. NK cell activation in (CBA X BALB/c)F1 mice with GVH reaction involves both host and donor cells and is preceded by an anti-host delayed-type hypersensitivity (DTH) response. B10 cells have a greater ability to induce DTH in B10F1 mice than cells from the opposite parent. We propose that NK cells are one group of non-specific effector cells recruited by DTH in a GVH reaction and may contribute to the tissue pathology.