Suppression of tumor cell growth by allospecific cytotoxic T-lymphocytes in vitro

Cytotoxic T-lymphocytes (CTLs) are the main cytotoxic effector cells of the immune system. Cytotoxic Tlymphocytes are able to control homeostasis by recognizing and eliminating the cells that were infected or underwent mutation or malignization. The results of our previous study of allospecific CTL lines (allo-CTL) demonstrated new regulatory functions of these cells. It was found that, despite the fact that allo-CTL lines exhibited strict specificity in killer activity tests, they drastically inhibited proliferation of activated lymphocytes of various haplotypes, including the syngeneic ones, irrespective of the specificity of CTLs. In particular, CTLs completely inhibited proliferation induced during response development in a mixed lymphocyte culture (MLC). A similar effect was observed when CTLs were added to mitogen-activated T-lymphocytes. However, CTLs almost had no effect on cell proliferation intensity in the syngeneic MLC and on spontaneous proliferation of nonactivated cells [1]. It is known that tumors occur as a result of uncontrolled proliferation of transformed cells. Growth of malignant tumors is determined primarily by the ability of these cells for intensive proliferation. It can be assumed that tumor cells may be the target for the regulatory effect of allo-CTLs. In this paper, we report the results of analysis of interaction of allo-CTLs with tumor cells in vitro. CTL lines showing specificity both for the entire complex of H-2 antigens and its subregions were obtained as described in [2]. The level of cytotoxic activity of CTLs was determined calorimetrically by the ability of target cells for lifetime inclusion of the Alamar Blue dye, which reflects their metabolic activity [3]. Mouse fibroblasts transformed with the SV-40 virus (C57BL/6SV (H- 2 b ), B10/D2SV ( H-2 d ), and C57BRSV(H-2 k ) ) were used as target cells. The proliferation intensity was assessed by incorporation of 3 H-thymidine. Flow cytometry was performed with a FACS Calibur cytofluorometer (Becton Dickinson). Allo-CTL phenotypes and the number of haploid cells were determined according to [4, 5]. The analysis of surface markers of obtained CTLs showed that these cells have the CD8 + ,