In vitro demonstration of in situ autologous tumour-cell cytotoxicity in MSV-induced tumours in A/SN mice

Abstract

Summary.-Moloney sarcoma-virus (MSV)-induced tumours in A/Sn mice have been dispersed with collagenase and DNase 8-15 days after virus inoculation, and both "sarcoma" and inflammatory cells separated by sedimentation velocity and adherence techniques. The isolated "sarcoma" cells had the morphological characteristics of atypical cells (i.e. cytoplasmic blebbing, vacuolization and prominent nucleoli) and were easily adapted to in vitro growth. As few as 2 x 103 of these cells inoculated i.m. produced new tumours within 8 days of injection in both syngeneic and allogeneic mice. Also, cell-free supernatant from "sarcoma"-cell cultures produced tumours, indicating that the successful transplantation of the "sarcoma" cells was probably due to production of infective virus. Cells cytotoxic in vitro against the ''sarcoma'' cells were present within both spleen and tumour of the tumour donors, but not in the spleens of normal mice. The cytotoxicity was specific against virusinfected cells, since in a mixture of virus-positive (gp 70) and virus-negative cells, positive cells were removed while negative cells were not affected, as measured by a visual cytotoxicity assay using immunostaining. Although T cells could be isolated from the MSV-induced tumours, these cells did not appear to mediate the cytotoxicity detected against the MSV "sarcoma" cells. These results suggest that early MSV infections might be sensitive to cytotoxic mechanisms distinct from those reported with established MLV-or MSV-induced tumour lines.

Non‐T‐cell‐mediated cytotoxicity in MSV tumor‐bearing mice. III. Macrophage‐mediated cytotoxicity against autochthonous MSV tumor‐isolated target cells

“…T cells are present neither in the spleen nor in the tumor (Becker and Haskill, 1980~). Regression therefore must depend on inflammatory processes regulated by T cells but not by their cytolytic effect.…”

“…These cells inhibited T-cell mitogen responses, antibody responses and proliferation of lymphoma cells. When the studies were extended to MSV-intratumoral mechanisms, macrophages were found with non-specifically cytostatic (Holden et al, 1976) and cytolytic (Puccetti and Holden, 1979) effects against in vitro tumor lines.In a series of experiments analyzing the nature of the morphologically atypical presumptive sarcoma cells isolated from MSV tumors, we found that these cells were highly virus-infected but not transformed (Becker and Haskill, 1980~). Thus it was of interest to investigate whether the granulocytes and macrophages, the two predominant inflammatory cell types present in these tumors, were active against the autochthonous virus-releasing cells responsible for propagation of the MSV lesion, In the first paper we investigated the cytolytic capacity of the granulocytes (Becker and Haskill, 19806).…”

“…In a series of experiments analyzing the nature of the morphologically atypical presumptive sarcoma cells isolated from MSV tumors, we found that these cells were highly virus-infected but not transformed (Becker and Haskill, 1980~). Thus it was of interest to investigate whether the granulocytes and macrophages, the two predominant inflammatory cell types present in these tumors, were active against the autochthonous virus-releasing cells responsible for propagation of the MSV lesion, In the first paper we investigated the cytolytic capacity of the granulocytes (Becker and Haskill, 19806).…”

Immunity against moloney sarcoma virus in H-2Db mutant bm14 mice. Unimpaired tumor immunity despite absence of a virus-specific cytotoxic T-cell response

“…Sera containing the highest titer of neutralizing antibodies are also the most effective in preventing M-MSV tumorigenesis, suggesting that neutralizing antibodies are probably responsible for this in vivo protection (LCvy and Leclerc, 1977). An alternative possibility emerges from studies by Becker and co-workers (Becker and Klein, 1980;Becker and Haskill, 1981), who were unable to demonstrate CTL in the N S n mouse during M-MSV tumor development and regression. They speculated that both cytotoxic granulocytes and macrophages, demonstrable in M-MSV tumors in this mouse strain, might play a role in regression of the tumor (Becker and Haskill, 1981).…”

“…An alternative possibility emerges from studies by Becker and co-workers (Becker and Klein, 1980;Becker and Haskill, 1981), who were unable to demonstrate CTL in the N S n mouse during M-MSV tumor development and regression. They speculated that both cytotoxic granulocytes and macrophages, demonstrable in M-MSV tumors in this mouse strain, might play a role in regression of the tumor (Becker and Haskill, 1981). However, it remains to be elucidated whether these effector cells alone are capable of causing tumor regression.…”