Cytotoxic T lymphocytes reactive against a syngeneic murine tumor and their specific suppressor T cells are both elicited by in vitro allosensitization

Chemo-immunotherapy of murine solid tumors: enhanced therapeutic effects by interleukin-2 combined with interferon alpha and the role of specific T cells

The aim of the present study has been to assess the therapeutic efficacy of various cytokines, singly or in combination, with and without chemotherapy (cyclophosphamide, Cy), in mice carrying advanced, weakly immunogenic tumors (MCA-105 sarcoma, M109 carcinoma). Treatment of animals with i.p. growths or experimental pulmonary metastases began 8-18 days after i.p. or i.v. tumor cell inoculation respectively. None of the cytokines tested [interleukin-2 (IL-2), interferon alpha (IFN alpha), tumor necrosis factor alpha (TNF alpha) and macrophage-colony-stimulating factor (M-CSF)] nor Cy had by itself a significant curative effect. A synergistic therapeutic effect was obtained with IL-2 or IFN alpha (but not with TNF alpha or M-CSF) in combination with Cy. The most efficacious regimen (65%-90% cure of mice carrying i.p. tumors) was the combination of Cy+IL-2+IFN alpha. Preliminary experiments suggested that sequential administration of these cytokines might be more beneficial than concurrent administration. Following successful immunotherapy, long-term (3-6 months) survivors showed a tumor-specific resistance to a second tumor challenge and their spleen contained an increased number of specific antitumor cytotoxic T lymphocyte precursors (5- to 20-fold, compared to control mice). In vitro and in vivo cell-depletion experiments using monoclonal antibodies revealed that T cells (primarily CD8), but not NK cells, are crucial for the therapeutic effects. This study indicates that a potent specific antitumor T cell immunity can be elicited against advanced weakly immunogenic tumors by combining chemotherapy (Cy) with IL-2 and IFN alpha.

The effect of class II gene transfection on the tumourigenicity of the H-2K-negative mouse leukaemia cell line K36.16

There is much evidence to suggest that potentially immunogenic tumour cells can escape cytolytic immune destruction by loss of class I antigen expression. Many tumours are allele-specific class I negative and, in murine systems, reconstitution of class I expression by gene transfection leads to an increase in tumour immunogenicity. In many systems where mice have rejected class I transfected tumour cells they are also immune to a subsequent challenge with the untransfected parent tumour. In this study we have examined the effect of stable class II antigen expression (induced by gene transfection) on a class I loss mutant (H-2Kk negative) murine cell line, K36.16. We show that H-2Ek expression is more effective at increasing tumour immunogenicity than the reconstitution of H-2Kk expression in these cells. This suggests that the induction of class II antigen expression on tumour cells may provide an effective way of enhancing tumour-specific immune responses in vivo.