Relation of H-2 expression on murine RCT(+) sarcoma cells to lung colonization and sensitivity to NK cells.

Murine RCT(+) sarcoma cells were sorted using a fluorescence-activated cell sorter with regard to the expression of H-2 antigens and then an increased H-2-expressing subclone was established, and named RCT(+)H-2+. The experimental metastasis of RCT(+) cells was compared with that of RCT(+)H-2+ cells by counting pulmonary colonies on the 21st day after i.v. inoculation of tumor cells (5-10 x 10(4)/mouse). When mice were inoculated with RCT(+) cells, mean numbers of pulmonary colonies were 2.1(range 0-6), 2.8(range 0-7) using 5 x 10(4) and 1 x 10(5) cells, respectively. On the other hand, in the mice inoculated with RCT(+)H-2+ cells, figures obtained were 7.0(range 4-16), 31.9(range 13-79), using 5 x 10(4) and 1 x 10(5) cells, respectively. The survival rate of RCT(+)H-2+ cells was higher than that of RCT(+) cells, when this was assayed in the early stage after i.v. injection of 51Cr-labeled cells (1 x 10(5) cells/mouse). In addition, RCT(+)H-2+ cells were more resistant than RCT(+) cells to lysis mediated by natural killer cells. These data suggest that an increase in metastatic ability was paralleled by an increase in the H-2 antigen expression and a decrease in sensitivity to the natural killer cells.