Human tumor-lymphocyte interaction in vitro. VII. Blastogenesis and generation of cytotoxicity against autologous tumor biopsy cells are inhibited by interferon

Autologous mixed lymphocyte-tumor reaction and autologous mixed lymphocyte reaction. II. Generation of specific and non-specific killer T cells capable of lysing autologous tumor

The specific and non-specific nature of autotumor cytotoxicity induced in autologous mixed lymphocyte-tumor culture (AMLTC) and autologous mixed lymphocyte culture (AMLC) was studied in patients with carcinomatous pleural effusions. Small- and medium-sized blood lymphocytes that were isolated by centrifugation on discontinuous Percoll gradients did not lyse autologous, freshly isolated effusion tumor cells. In vitro activation of the small lymphocytes, but not of the medium lymphocytes, with autologous tumor cells generated cytotoxic potential restricted to autologous tumor. When stimulated with autologous non-malignant non-T cells, the medium lymphocytes, but not small lymphocytes, were triggered to cytotoxicity that acted not only on autologous tumor cells but also on allogeneic tumor cells, T blasts, and tumor cell lines. Experiments using monoclonal antibodies (MAb) and complement (C') showed that both types of killer cells were CD2+ CD3+ CD16- T cells. Autotumor cytotoxicity developed in AMLTC was mediated by the CD4- CD8+ T cell subset in 6 of 9 cases and the CD4+ CD8- subset in the other 3 cases. In contrast, cytotoxicity induced in AMLC was exerted exclusively by the CD8+ subset. The enrichment of blasts from cultured T cells on discontinuous density gradients enhanced autotumor killing activity, with no reactivity recorded for blast-depleted, resting T cells. Addition of mitomycin-C-treated large granular lymphocytes (LGL) to AMLTC abolished the induction of autotumor killer cells, whereas non-specific killer cells were generated in AMLC irrespective of the presence of LGL. These results indicate that stimulation of autoreactive T cells in AMLTC and in AMLC could induce 2 distinct types of autotumor killer cells.

Influences of sodium diethyldithiocarbamate, DTC (imuthiolR) on T cell defective responses of aged BALB/c mice

The effect of chronic imuthiol treatment, 25 mg/kg weekly for 4 months initiated at the age of 12 months, on T-cell functions of aged female BALB/c mice was investigated. Imuthiol restored to normal value the impaired response to Concanavalin A (Con A) and enhanced the proliferative response to phytohemagglutinin (PHA). Impaired cytotoxic T-cell activity (CTL), was restored near to the value of young controls by imuthiol. Serum thymic factor (FTS) levels in serum of treated aged animals outpassed those of untreated young mice. Delayed-type hypersensitivity (DTH) reaction to oxazolone was increased. In contrast, the graft-vs-host (GVH) mortality induced by injecting H-2 histoincompatible cells to irradiated recipients, which GVH was impaired by aging, was not significantly modified by imuthiol. The excessive cytotoxicity for chicken red cells of macrophages (ADCC) from aged mice was reduced, as well as macrophage cytotoxicity for tumor cells. Natural killer cell activity remained unchanged. This finding confirms that imuthiol enhanced effectively T cell-dependent responses but the data on GVH reaction suggest that its effects are under a complex mode of action. Restoration of a normal production of FTS may be one mechanism by which imuthiol acts on the reinduction of the T-cell differentiating pathway in aged mice.

Effect of interferon on cell proliferation and generation of cytotoxic potential in mixed autologous and allogeneic lymphocyte cultures

Autologous and allogeneic mixed lymphocyte cultures (AMC and MLC) were assayed for blastogenesis, generation of cytotoxic potential, and the effect of interferon (IFN-alpha) on these features. The cells of the mixed cultures lysed K562, Daudi, and autologous and allogeneic phytohaemagglutinin blasts. Stimulator-specific cytotoxicity was observed only in MLC. B blasts induced with Staphylococcus aureus were only affected in a stimulator-specific manner. Short-term IFN treatment of the MLC-derived effectors before the lytic assay enhanced the nonspecific component of cytotoxicity. Cell proliferation was considerably lower in AMC than in MLC. This was decreased when IFN-alpha was added at the initiation of the cultures. The presence of IFN influenced the generation of lytic potential. Comparison of the lysis of the different targets exerted by MLC-activated cells suggested that the specific component was more substantially elevated than the nonspecific one. It is likely that the IFN induced such modifications in the culture conditions that favoured the proliferation of the specific clone. Re-exposure of lymphocytes cultured in the presence of IFN to another dose of IFN before the assay had no influence on their lytic potential.

IFN-alpha-induced modulations of the events in human mixed lymphocyte cultures

Autologous mixed lymphocyte cultures (AMC) with T-enriched subset of human blood lymphocytes as responders and B-cells or plastic adherent cells as stimulators and allogeneic mixed lymphocyte cultures (MLC) were assayed for blastogenesis and generation of cytotoxic potential. The activated cells lyzed K562 and Daudi, autologous and allogeneic PHA-blasts. The AMC population affected the autologous and allogeneic blasts at a similar strength and there was no indication for selective effects. B-Blasts induced with Staphylococcus aureus were not lyzed. The MLC populations had a stimulation-specific cytotoxic component. This was revealed by the stronger effect against the stimulator PHA-blasts and by the lysis of the stimulator B-blasts. Short-time interferon (IFN) treatment prior to the lytic assay enhanced the anti-Daudi and anti-K562 lytic activity of the AMC and MLC populations. With AMC the lytic efficiency against the autologous and allogeneic PHA-blasts were not changed while with MLC they were also elevated. This increase was confined to the non-specific component of the cytoxicity. The proliferation of lymphocytes was suppressed when interferon was added at the initiation of the mixed cultures. On a per-cell basis the cytotoxic potential of these cultures were stronger. In the MLC the stimulation-specific component increased more substantially than the effect against the non-specific targets. It is possible that the IFN-induced modification of the culture conditions such as suppression of the initial proliferation favored the growth of the specific clone. Re-exposure of these cells to another dose of interferon prior to the lytic assay had no effect on the lytic potential.

Lymphokine-activated killer cell phenomenon. Lysis of natural killer-resistant fresh solid tumor cells by interleukin 2-activated autologous human peripheral blood lymphocytes

Activation in lectin-free interleukin 2 (IL-2) containing supernatants of peripheral blood mononuclear leukocytes (PBL) from cancer patients or normal individuals resulted in expression of cytotoxicity toward 20 of 21 natural killer (NK)-resistant fresh solid tumor cells tested. Fresh solid tumor cells were resistant to NK-mediated lysis in 10 autologous patients' PBL-tumor interactions, and from 17 normal individuals tested against 13 allogeneic fresh tumors. Culture of PBL in IL-2 for 2-3 d was required for the lymphokine activated killers (LAK) to be expressed, and lytic activity toward a variety of NK-resistant fresh and cultured tumor targets developed in parallel. Autologous IL-2 was functional in LAK activation, as well as interferon-depleted IL-2 preparations. Irradiation of responder PBL before culture in IL-2 prevented LAK development. Precursors of LAK were present in PBL depleted of adherent cells and in NK-void thoracic duct lymphocytes, suggesting that the precursor is neither a monocyte nor an NK cell. LAK effectors expressed the serologically defined T cell markers of OKT.3, Leu-1, and 4F2, but did not express the monocyte/NK marker OKM-1. Lysis of autologous fresh solid tumors by LAK from cancer patients' PBL was demonstrated in 85% of the patient-fresh tumor combinations. Our data present evidence that the LAK system is a phenomenon distinct from either NK or CTL systems that probably accounts for a large number of reported nonclassical cytotoxicities. The biological role of LAK cells is not yet known, although it is suggested that these cells may be functional in immune surveillance against human solid tumors.

Cellular and humoral in vitro cytotoxicity against autologous bladder tumor cells in humans. Differences in autologous cytotoxicity against non-invasive and invasive transitional-cell tumors of the urinary bladder

Lymphocyte-mediated cytotoxicity (LMC), antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) were measured in a 51Cr assay against autologous tumor cells from 7 patients with non-invasive and 9 patients with invasive transitional-cell tumors of the urinary bladder (TCC). Cytotoxicity against the invasive tumor cells were demonstrated in CDC. Heat-inactivation of sera lead to complete loss of cytotoxicity while addition of allogenic serum restored cytotoxicity. The cytotoxicity of allogenic sera from controls against invasive tumor targets showed no differences when compared with autologous sera. No or very weak cytotoxicity was found against non-invasive tumor targets in autologous or allogenic assays. LMC and ADCC showed weak or no reactivities. Intensive wash or trypsinization of effector cells did not affect the cytotoxicity in LMC. The results indicate the occurrence of complement-dependent antibodies directed against target cells from invasive tumors of the urinary bladder while no cytotoxic responses were detectable when the target cells originated from non-invasive tumors.

Tumor biopsy cells participating in systems in which cytotoxicity of lymphocytes is generated. Autologous and allogeneic studies

Freshly separated tumor cells from sarcomas and carcinomas were used in various roles in lymphocyte-target cell interaction assays. They were poorer allogeneic stimulators than lymphocytes. They were however good allotargets for the cytotoxicity generated in mixed lymphocyte cultures. They were also killed as third party targets by lymphocytes activated in MLC. In a proportion of experiments, lymphocytes activated in MLC killed autologous tumor cells. Autotumor killer effect was generated in the majority of mixed cultures containing lymphocytes and tumor biopsy cells from the same individual. Generation of cytotoxicity against K562 was a good measure of lymphocyte activation and could be used as a sensitive indicator for the occurrence of the recognition step in the mixed cultures. We propose that for the search of lymphocytes with specific receptors, activation is a more reliable parameter than specific cytotoxicity since the latter function is also influenced by the sensitivity of the target. The results confirmed that patients with carcinomas and sarcomas possess autotumor-reactive lymphocytes. These can be activated for cytotoxicity by in vitro confrontation with the tumor cells and occasionally through stimulation which is unrelated to the tumor cells.