The requirement for monocytes in spontaneous cytotoxicity by lymphocytes from healthy donors and melanoma patients

Functional and phenotypic characteristics of bovine natural cytotoxic cells

Bovine natural cytotoxic (NC) cell activity of peripheral blood leukocytes (PBL) was studied in a chromium release assay, using xenogeneic tumor cells (YAC-1, P815) and herpes virus-infected bovine fibroblasts. The activity pattern resembled that of murine natural killer cells, in that YAC-1 cells were readily lysed, whereas P815 cells were resistant. However, 10-16 h of incubation were usually required to give appreciable cell lysis. Low, but consistent NC-activity was expressed against virus-infected fibroblasts. Using various biophysical and biochemical cell-separation methods, it was found that the effector cell active against both the xenogeneic tumor cells and virus-infected fibroblast belonged to the mononuclear phagocyte system. The indications are that at least two subpopulations of the blood monocytes, differing perhaps in maturation or clonal derivation, express NC-activity.

In vitro cytotoxicity of lymphocyte subpopulations against autologous human bladder tumor cells

The in vitro cytotoxicity of unfractionated blood lymphocytes and T and non-T lymphocytes respectively, was tested against autologous tumor cells from 21 patients with grade III-IV urothelial bladder carcinomas. Generally, little or no cytotoxicity was seen. However, some differences in autologous cytotoxicity between T and non-T lymphocytes were detectable. Four of 21 patients had cytotoxic non-T lymphocytes against autologous bladder tumor cells. The results indicate, that the effector cells are primarily non-T lymphocytes, and that cytotoxicity appears at lower levels of T lymphocytes in unfractionated lymphocyte preparations.

Isolation of human NK cells by density gradient centrifugation

Sedimentation characteristics of human NK cells in discontinuous Percoll density gradients were studied. NK activity against the leukaemic cell line K-562 peaked in a single low density fraction mainly consisting of large granular lymphocytes previously shown to be the principal NK cells in human peripheral blood. Percoll density gradient centrifugation provides a useful tool for analysis of human NK cells and their relationship to other blood mononuclear cells.