Effect of lymphoma grafts on natural killer cell activity in AKR and C57BL/6 mice.

The natural killer (NK) cell activity of spleen suspensions was measured in AKR and C57BL/6 mice grafted either with isogeneic thymic or nonthymic lymphomas. The transplanted cells originated from lymphoid tumors (B, T, or null) which developed either spontaneously (AKR) or after radiation exposure or after injection of retroviruses (C57BL/6). The NK response was significantly enhanced in AKR and C57BL/6 mice grafted with nonthymic and with some thymic lymphoma lines maintained by in vivo passages. The increase of NK activity which took place during the first 5 days after grafting was concomitant with a hyperplasia of the spleen red pulp. Cells from invaded spleens presented a suppressive effect on NK activity. Most primary AKR thymomas and 4 out of 8 tested thymic lymphomas maintained by in vivo passage in C57BL/6 mice were not inducers. In vitro passaged lymphomas, whether AKR or C57BL/6, displayed variable capacity of stimulation which did not match those of the same in vivo maintained lines. It was found that the capacity of most cultured cells to stimulate NK activity correlated positively with the reverse transcriptase concentration of the corresponding culture media.