| Abstract: | Blast natural killer (NK) cells were elicited in the spleens of mice by treatments with the interferon inducers lymphocytic choriomeningitis virus (LCMV) or polyinosinic-polycytidylic acid (poly I:C). The blast-NK cells, separated on the basis of size by centrifugal elutriation, were compared with blast cytotoxic T lymphocytes (CTL) generated during infection with LCMV. In vivo treatments with antibody to asialo GM1 (AGM1) blocked the appearance of blast-NK cells but not blast-CTL. Antibody and complement depletion experiments indicated that the blast-NK cells were AGM1+, NK 1.2+/-, Lyt-5+/-, Thy+/-, Qa-5/NK 1.1+, Lyt-2-, B23.1-, and J11d-. Blast-NK cells could be unequivocally distinguished from blast-CTL, because the blast-CTL were completely sensitive to treatments with anti-Lyt-2 and complement, whereas the blast-NK cells were completely resistant. The blast-NK cells were purified from populations of large-size cells by antibody and complement treatments that depleted the co-eluting monocyte/macrophages and polymorphonuclear leukocytes. The population resulting after separation from dead cells over Percoll gradients represented approximately 1% of the total spleen cells, contained greater than 60% large granular lymphocytes and mediated greater than 15% killing of YAC-1 target cells in a 4-hr 51Cr release assay at an effector to target cell ratio of 1:1. The purified blast-NK cells lysed a broad range of target cells at relatively low effector to target cell ratios. The order of sensitivity of the target cells was YAC-1 much greater than K562 approximately equal to L-929 much greater than P815, consistent with that reported for NK cell-mediated lysis. The ability of the blast-NK cells to mediate lysis of NK cells also was examined. The purified NK cells mediated significant levels of lysis against the NK-like cloned line, NK1B6B10, in a 51Cr release assay. Furthermore, the purified blast-NK cells mediated lysis of bound blast-NK cells in a single-cell agarose assay. These results indicate that highly purified blast-NK cells are exceptionally efficient at mediating lysis and suggest that NK cells may act to negatively regulate the proliferation of NK cells by lysing other NK cells. |
