Mixed lymphocyte/tumor-cell interaction in a murine sarcoma virus (Moloney)-induced tumor system. Comparison between lymphoproliferation and lymphocyte cytotoxicity

Effect of recombinant human interleukin 2 on the growth of a BALB/c sarcoma induced by Moloney murine sarcoma virus

The effect of in vivo administration of recombinant interleukin 2 (rIL2) on the growth of a primary female BALB/c sarcoma induced by Moloney murine sarcoma virus (M-MSV) was studied. Although low-dose administration of (6,000 JU/mouse x 14 days) rIL2 had no effect on the growth of the tumors, high-dose (15,000-80,000 JU/mouse x 14 days) intraperitoneal inoculation of rIL2 induced tumor regression, dose-dependently. Tumors in mice which received 80,000 JU/mouse/day of rIL2 regressed completely 2 weeks after the initiation of treatment. The survival rates of the treated groups were significantly higher than those of the control group. A time course experiment disclosed that the effect of rIL2 was restricted only to the group in which rIL2 treatment started 8 days after the inoculation of M-MSV. The cytotoxic activity of regional lymph node lymphocytes from rIL2-treated mice was demonstrated against primary culture of M-MSV-induced sarcoma but not against syngeneic tumor induced by methylcholanthrene (Meth A). The effect of rIL2 was partially blocked by the administration of anti-IL2 receptor antibody. Immunohistochemical examination revealed that infiltration of Thy1.2+Lyt1+2- (helper/inducer subset) lymphocytes into the tumor tissue was prominent in mice which received high-dose rIL2. The results indicated that IL2 induced regression of M-MSV-induced sarcoma mainly through activation of IL2-receptor-positive helper T cells in the tumor tissues and of killer cells in the draining lymph nodes.

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

It was shown previously that B6.C-H-2bm14 (bm14) mice, carrying a mutation in the H-2Db locus, are unable to generate cytotoxic T cells (CTL) against Moloney murine sarcoma virus (M-MSV). We now report an analysis of tumor induction and regression kinetics and of immunity to the virus, following the injection of graded doses of M-MSV into C57BL/6 (B6) and bm14 mice. Contrary to expectation, bm14 mice showed slightly less tumors than wildtype B6 mice. Moreover, all bm14 mice that developed a tumor were able to reject this tumor, even after injection of the highest virus dose tested. From the spleen cells of bm14 mice that had rejected tumors, no secondary in vitro CTL responses could be generated, in contrast to strong CTL responses generated from B6 spleen cells. Although bm14 mice were unable to generate virus-specific CTL, they showed normal antibody and T-cell proliferative responses against Moloney virus, suggesting an intact T-helper-cell function. It is concluded that in bm14 mice, under the conditions tested, virus-specific CTL are not generated despite excellent tumor immunity. Therefore, this CTL response is not necessary for protection against M-MSV-induced tumors. Protection is likely to be mediated by a normal T-cell proliferative response.

Murine sarcoma virus (MSV)-induced tumors in mice. I. Distribution of MSV-immune cytolytic T lymphocytes in vivo

Quantitative studies using a 51Cr release assay were performed to analyse the time-course of appearance and specificity of cytolytic cells in C57Bl/6 mice inoculated with Moloney murine sarcoma virus (MSV). Various lymphoid organs were studied including spleen, mesenteric lymph nodes (MLN), lymph nodes regional to the MSV-induced tumor (RLN), and peripheral blood. Furthermore, the kinetics of appearance of cytolytic cells within the MSV-induced tumor was determined. In agreement with previous studied, it was found that cytolytic T lymphocytes (CTL) specific for MSV-associated antigens were present among the cells extracted from the tumor and from the lymphoid organs. However, differences in the kinetics of CTL activity could be documented: lymphoid cells from spleen, RLN and peripheral blood showed peak activity at the time of maximum tumor diameter, while intratumoral cells showed peak activity at the onset of tumor regression. MLN cells showed cytolytic activity only when tumor regression had begun. Naturally cytotoxic cell populations of thymus-independent origin, present in normal control mice, were also detected in MSV-infected mice.