Natural killer (NK) cells and graft-versus-host disease (GVHD): no correlation between the NK cell levels and GVHD in the murine P----F1 model.

Graft-versus-host disease (GVHD) was induced in (CBA X C57BL/6) F1 mice by i.v. injection of 50 X 10(6) parental spleen cells. The GVHD induced an enhanced NK (anti-YAC-1) cytotoxicity during the first 2 weeks after the spleen cell transfusion. This cytotoxic activity was shown to be mediated by asialo GM1-positive, partially Thy-1-positive and nylon-wool (NW) non-adherent cells, thus being classical NK cells. Depletion of NK-cell activity from donor and/or recipient mice with anti-asialo GM1 antibody prior to the spleen cell transfer did not prevent the GVHD as judged by the splenomegaly assay. Also, when NK activity was potentiated with polyinosinic-polycytidylic acid (pIC), no effect on the GVHD was seen. These data suggest that NK cells are not crucial for the development of GVHD in this model.