Flow cytometric characterization of proliferating natural killer lymphocytes from bone marrow donors in the mixed...

Detection of natural killer (NK) cells in the mixed lymphocyte reaction (MLR) was investigated by flow cytometry and cytotoxicity toward the K562 cell line. Peripheral blood mononuclear cells (PBMCs) from normal individuals were stimulated with either lymphoblastoid cell lines (LCLs) or PBMCs. This approach allowed the following observations: 1) after stimulation by LCLs, the percentage of NK cells increased concomitantly with the level of cytotoxicity, in contrast to when PBMCs were used as stimulators; 2) anti-interleukin-2 monoclonal antibody strongly inhibited NK proliferation in the MLR, but antibody to interferon gamma did not; and 3) purified NK cells were unable to proliferate against LCLs. All these data suggest that NK cells induced by LCL stimulators depend on T cells to proliferate in the MLR. Flow cytometric detection of NK cells in the MLR was also used on cryopreserved PBMCs from 31 bone marrow donors, because it has been reported that an enhanced donor NK cell activity was correlated with the development of graft-versus-host disease after HLA-identical sibling bone marrow transplantation. NK cell proliferation under LCL stimulation was intense and varied greatly among the donors tested. However, no statistical correlation was observed between LCL-induced donor NK cell proliferation in the MLR and the occurrence of graft-versus-host disease after bone marrow grafting.