Mixed Lymphocyte Tumor Cell Culture Research Articles

Auto-tumor recognition following in vitro induction of MHC antigen expression on solid human tumors: stimulation of lymphocytes and generation of cytotoxicity against the original MHC-antigen-negative tumor cells.

Expression of major histocompatibility complex (MHC) class I antigens was induced in eight out of nine freshly prepared tumor cell suspensions by exposure to interferon (IFN gamma) and tumor necrosis factor (TNF alpha) in vitro. The untreated, class-I-antigen-negative, and the treated, antigen-positive, cells of three tumors (one breast carcinoma, one plasmocytoma and one ovarian carcinoma) were compared for the capacity to stimulate autologous and allogeneic blood lymphocytes, to generate auto-tumor cytotoxicity and for sensitivity to the lytic effect induced in autologous mixed lymphocyte tumor cell culture (MLTC). The MHC class I-negative cells did not stimulate, while the cells induced for expression of antigens did. On the other hand, when the autologous cytotoxic cells were generated in the MLTC by the class I antigen-positive tumor cells the class I-negative tumor cells were also damaged. Lysis of the class-I-positive tumor cells was abrogated by the W6/32 monoclonal antibody directed against the monomorphic part of the class I molecules.

Anti-idiotypic antibodies against UV-induced tumor-specific CTL clones. Preparation in syngeneic combination.

In this study, we first established several CTL clones of (BALB/c x C57BL/6)F1 origin that were specific for either syngeneic UV female 1 or UV male 1 fibrosarcoma cell lines. All the CTL clones had Thy-1+ Lyt-2+ L3T4- phenotypes and showed Kd restriction when lysing the corresponding target cells. Sera obtained from syngeneic animals immunized with three CTL clones, 10B-5 for UV female 1, and CTL9 and CTL10 for UV male 1, showed specific inhibition of target cell lysis with the corresponding CTL clones. The inhibitory activities were found in sera of the majority of immunized animals. Because the inhibitory activity resides in protein A-binding fraction, mAb were produced by hybridizing spleen cells of hyperimmune animals. N1-56 was thus obtained from a mouse immunized with 10B-5 CTL clone reactive with UV female 1. N1-56 was clonotype specific, reacting with 10B-5 but not with other CTL lines or leukemia cell lines. No N1-56+ cells were detectable in thymocytes, lymph node cells, or spleen cells of either naive or UV female 1-immune CB6F1 mice. Immunoprecipitation showed that N1-56 reacts with 90,000 Mr molecules on 10B-5 CTL clone under nonreducing conditions and 45,000 Mr molecules under reducing conditions, indicating its reactivities with idiotypic determinants of TCR on the CTL clone. N1-56 inhibited lytic activity of 10B-5, but neither N1-56 nor alpha-10B-5 hyperimmune serum inhibited that of alpha-UV female 1 mixed lymphocyte tumor cell culture cells. N1-56 induced proliferation of 10B-5 without addition of Ag.

Importance of MHC antigen expression on solid tumors in the in vitro interaction with autologous blood lymphocytes.

In 54 patients with lung and 14 with ovarian carcinomas the quantitative variations of the major histocompatibility complex (MHC)-determined class I and class II antigens of the tumor cells were related to their in vitro interaction with blood lymphocytes, to the lymphoid infiltration of the tumors, and to the metastatic state of the disease. The tumor cell-lymphocyte interaction was measured by the proliferative response in mixed lymphocyte tumor cell culture and by the cytotoxic activity of the lymphocytes. The results showed that (1) none of the 23 tumors from patients with disseminated disease were lysed; (2) class I-negative tumors were not damaged; (3) lymphoid infiltration was present in a higher proportion of class II-positive tumors; and (4) both MHC-positive and -negative tumors were found among the disseminated tumors. The requirement of class I expression in the lytic interaction substantiates our earlier conclusion concerning the cytotoxic T lymphocyte nature of lymphocyte-mediated auto-tumor lysis. The lack of auto-tumor lysis in patients with metastases suggests impairment of lymphocyte function in advanced stages of the disease.

Suppressor cells in the effector phase of autologous cytotoxic reactions in cancer patients.

Cytotoxicity was induced in lymphocytes (CL) from 10 out of 15 patients by autologous mixed lymphocyte tumor cell culture and further cultivation with recombinant interleukin-2. In cells from 3 of the 10 patients, cytotoxicity was suppressed by more than 50% when autologous peripheral blood mononuclear cells (PBMC) from the patients with large tumors were added to the autologous killing system. The cells responsible for suppressing the cytotoxicity in the effector phase were adherent or nonadherent to plastic depending on the patient examined. The T cell fraction from 1 patient significantly suppressed the cytotoxic activity, and this suppression was seen only in the autologous system. On the other hand, plastic adherent cells but not T cells from PBMC of 2 subjects suppressed the cytotoxic activity of CL. The reason why the main cell population suppressing the CL activity differed among the patients is unclear. However, the findings that the suppression was mostly abrogated following resection of the tumor mass suggested that suppressor cells, either of macrophage lineage or T cells, are induced in patients with a large tumor mass. This speculation is supported by the finding that the PBMC from a patient with tumor recurrence regained the suppressive activity.

Defective T helper activity in the spleen of BALB/c mice immune to a syngeneic fibrosarcoma.

BALB/c mice were immunized with the syngeneic 3-methylcholanthrene-induced fibrosarcoma CA-2 by the growth and excision method. When lymphoid cells from different organs of these tumor-free mice were tested in a direct 51Cr-release assay, peritoneal exudate cells but not spleen cells displayed specific cytotoxicity against the syngeneic tumor target. A cytotoxic response could be obtained by tumor-immune spleen cells when cultured in a mixed lymphocyte tumor cell culture (MLTC) at high but not low density although at the same effector/stimulator ratio. Lack of cytotoxic activity in low density MLTC was not due to an impairment of cytotoxic precursors since cytotoxicity was rescued by adding exogenous interleukin-2 in experimental conditions in which no lymphokine-activated killer cells could develop relevant anti-CA-2 lysis. When low density MLTC were supplemented with either 800 R-irradiated cells or nonirradiated, negatively selected Lyt 1+ cells from the same immune mice, induction of a cytotoxic response against CA-2 occurred and interleukin-2 production became detectable. Additional studies indicated that spleen cells of CA-2-immune mice were also impaired in their ability to provide help to syngeneic thymocytes for the generation of cytotoxic T lymphocytes against C57BL/6J alloantigens. Dilution effect of helper cells due to immunization procedures was excluded since spleen cells of mice immunized against another BALB/c tumor, the YC8 lymphoma, or against DBA/2 minor histocompatibility antigens provided good help to thymocytes against the same alloantigens. These results indicate that tumor-immune animals may also have selective T helper defects in an important lymphoid organ like spleen.

Lysis of autologous tumor cells by blood lymphocytes activated in autologous mixed lymphocyte tumor cell culture--no correlation with the postsurgical clinical course.

Mixed lymphocyte tumor cell cultures (MLTC) were initiated with cells collected at the time of surgery from 62 patients with the following diagnoses: 12 squamous cell carcinoma, 14 adenocarcinoma of the lung, 17 osteosarcomas, and 16 soft tissue sarcomas. The lytic effect generated against autologous tumor cells was tested on the 7th day. These patients had been part of previous evaluation, which revealed that the lysis of autologous tumor cells by freshly collected lymphocytes correlated with the postsurgical clinical course. Patients with long survival exhibited autotumor lysis without previous activation. Blood lymphocytes of about half of the primarily nonreactive patients were stimulated for lytic function in MLTC. However, this parameter showed no correlation with the clinical course.

Functional activity in vivo of effector T cell populations. III. Protection against Moloney murine sarcoma virus (M-MSV)-induced tumors in T cell deficient mice by the adoptive transfer of a M-MSV-specific cytolytic T lymphocyte clone.

The functional activity of Moloney murine sarcoma virus (M-MSV)-specific T lymphocytes in vivo was assayed by the i.v. injection of virus-specific T lymphocytes into T cell-deficient "B mice". Virus-specific T lymphocytes generated in mixed lymphocyte tumor cell cultures were transferred i.v. into syngeneic "B mice" injected simultaneously at a distant site with the virus. These experiments indicated that a low dose (1 X 10(6) cultured cells) of infused lymphocytes can afford protection. To define the T lymphocyte subpopulation which was active, Lyt-2+ lymphocytes were selected by "panning" on plastic petri dishes coated with anti-Lyt-2 monoclonal antibody, and Lyt-2- lymphocytes selected by treatment with anti-Lyt-2 monoclonal antibody and complement. The results indicated that a Lyt-2+ lymphocyte-enriched population was more efficient in conferring protection against M-MSV-induced tumors. To investigate if cytolytic T lymphocytes (CTL) alone had a protective effect, a M-MSV-specific CTL clone was transferred in the same model system. The results demonstrated that a M-MSV-specific CTL clone prevented M-MSV-induced tumor growth and also induced the destruction of syngeneic Moloney murine leukemia virus (M-MuLV)-induced MBL-2 leukemic cells in the peritoneal cavity. However, the cell dose required to obtain protection using a CTL clone was higher than that which was effective when mixed lymphocyte tumor cell culture cells were used. To assess the ability of the transferred cells to home and to repopulate the lymphoid organs of the "B mice", the frequency of virus-specific CTL precursors in the spleen was evaluated by limiting dilution analysis. The results indicated that lymphocytes from mixed lymphocyte tumor cell cultures can be recovered from the spleens of "B mice" injected i.v. 25 days earlier. On the contrary, following the transfer of an active CTL clone, a very low frequency (less than 1/200,000 cells) of virus-specific CTL precursors was present in the spleens of recipient animals. The same M-MSV-specific CTL clone did not yield protection against M-MSV-induced tumors or MBL-2 leukemic cells when injected i.v. into M-MuLV tolerant mice.

Differences of Sensitivity to Autologous Cytotoxic Lymphocytes Between Primary Tumor and its Cervical Lymph Node Metastases

Antigenic differences between primary tumors and their cervical lymph node metastases of 12 patients with head and neck cancers were examined by measuring their sensitivity to cytotoxic lymphocytes (CL). Cytotoxicity was induced by autologous mixed lymphocyte (CL). Cytotoxicity was induced by autologous mixed lymphocyte tumor cell culture (MLTC), and further cultivation with recombinant interleukin-2 (rIL-2). The effector cells which were used in this study consisted of OKT3+8+ and OKT3+4+ subpopulations. Their cytotoxic nature was different from lymphokine activated killer cell (LAK cell) activity. Cytotoxicity of CLs stimulated by autologous primary tumor cells (CLP) was observed in 7 out of 12 patients (58.3%). In contrast, cytotoxicity of CLs stimulated by metastatic tumor cells (CLM) was observed in 4 out of 12 patients (33.3%). In the cases in which both CLP and CLM were successfully induced, cross-reactivity tests and cold target inhibition tests were performed. These results suggested that a reduction in immunogenicity had occurred at the metastatic site, and sensitivity against autologous CL was different between primary and metastatic tumor cells.

Clonal analysis of cytotoxic T lymphocytes (CTL) against autologous melanoma. Classification based on phenotype, specificity and inhibition by monoclonal antibodies to T cell structures.

This study investigates the nature and specificity of cytotoxic T lymphocytes (CTL) in patients with melanoma which are able to kill autologous melanoma cells. Interleukin 2 (IL2)-dependent T cell clones from two melanoma patients and a normal subject were generated in mixed lymphocyte cultures (MLC) or mixed lymphocyte tumor cell cultures (MLTC) and propagated for prolonged periods in tissue culture. Analysis of their phenotype by a wide range of monoclonal antibodies (M.Abs) revealed two main phenotypes which depended on whether they expressed Fc receptors detected by Leu 11 M.Abs or not. Leu 11- T cells (referred to as Type 1) were inhibited by M.Abs to T3, T8, and a common HLA, ABC antigen. Conversely Leu 11+ T cells (referred to as Type 2) were inhibited by M.Ab to Leu 11 but not by M.Ab to T3, T8 and the HLA, ABC antigen. Subtypes among Type 1 cells were recognized which depended on their specificity. The most restricted were CTL [Type 1(a)] clones generated only in MLTC which recognized the autologous melanoma cell plus 1 of 11 other melanoma target cells. Type 1(b) CTL clones recognized a larger proportion (approximately 50%) of the melanoma cells. A third category [Type 1(c)] recognized antigens on melanoma cells shared with that on the EBV-transformed B cells used as stimulators in the MLC. Type 2 CTL clones had broad specificity to melanoma and nonmelanoma cells, characteristic of that described for lymphokine activated killer (LAK) cells. The latter were MHC unrestricted but further studies are required to clarify whether the Type 1 CTL clones are MHC restricted or not. The CTL activity of all clones was inhibited by M.Ab to the sheep red blood cell receptor and to the T10 antigens. It is suggested that recognition of these different types of CTL clones may assist future studies on the immune response against melanoma and the nature of antigens recognized by CTL.

同系しゅよう細胞に対するリンパ球混合培養応答の性状解析 インターロイキン３の産生誘導

Mitogenic responses and lymphokine productions of spleen cells of C3H/He mice in mixed culture with syngeneic tumor cells (mixed lymphocyte tumor cell culture, SMLTC) were studied. Spleen cells of C3H/He mice showed a mitogenic response to X5563, MH134 and MM48, syngeneic tumor cells expressing major class I histocompatible antigen (MHC), but not to MM46 without an expression of either class I or class II antigen. Mitogenic responses to these syngeneic tumor cells could be observed on day 1 and peaked on day 3. Accompanying this mitogenic response, an activity to induce proliferation of FDC-P 2 cells, a responder for interleukin 3 (IL-3), was detected in the SMLTC fluids. Interleukin 2 (IL-2) nor interferon (IFN) activities were not found in the culture fluids throughout the 2 weeks observation period. The chromatography on FPLC MonoQ column of the condensed SMLTC culture fluids revealed that the proliferative activity against FDC-P 2 was eluted from the column with the same pattern as those of IL-3 found in the culture fluids of WEHI-3 and EL-4 cells. Neither IL-2 nor IFN activity was found in the condensed SMLTC supernatants and their effluents from MonoQ column.Next, generation of cytotoxic effector cells against a stimulator cell line and an activity of natural killer (NK) cells in each SMLTC system were examined. The results showed that both cytotoxic activities, of which the generation required IL-2 and IFN, could not be found. In the SMLTC system, in which IL-3 production could be observed, a cytotoxic activity against MethA cells, a target for natural cytotoxic (NC) cells, was induced. These results indicate that tumor cells in interaction with syngeneic spleen cells induce mitogenic responses and produce IL-3 and IL-3-dependent nonspecific NC-like cells, but not IL-2 and IL-2 dependent their cytotoxic T cells and NK cells.

27] Cytolytic activity mediated by T lymphocytes

This chapter reviews the cytolytic activity mediated by T lymphocytes. Cytolytic T lymphocytes (CTL) are thought to play a major role in the immune defense system against virus infections and allografts and are most likely involved in immune responses to tumors. Highly enriched CTL populations and clones have been generated in vitro in allogeneic mixed lymphocyte cultures (MLC) or in syngeneic mixed-lymphocyte tumor-cell cultures (MLTC). The 51Cr release assay represents a simple, rapid, and quantitative means of assessing CTL-mediated cytolysis in vitro. It can also be used to monitor target cell lysis mediated by effector cells other than CTL. The generation of CTL activities in vitro, using MLC and syngeneic MLTC, has allowed a detailed analysis of the cell-mediated immune reactions that occur during a response to allografts or tumor growth. Moreover, the CTL populations, thus, obtained provide a convenient starting point for the derivation of cloned CTL lines, which then can be maintained in culture for months or years by periodic exposure to the appropriate antigen in the presence of filler cells and a source of interleukin 2.

Killer cells of feline leukemia virus- and feline sarcoma virus-infected transformed cells: The role of NK, ADCC, and in vitro generated cytotoxic cells

Feline white blood cells (WBC) manifested a primary in vitro mixed lymphocyte tumor cell culture (MLTC) proliferative response to feline leukemia virus-feline sarcoma virus (FeLV-FeSV)-infected transformed target cells, which reached a peak at Day 15. Furthermore, primary in vitro MLTC cultures generated cytotoxic killer cells capable of killing a variety of targets in non-major histocompatibility gene complex restricted fashion, and effector cells were capable of killing targets introduced repeatedly into cultures over a 49-day period. The presence of feline fibrosarcoma (f-sarc) stimulators was the primary driving force for proliferation and generation of killing because exogenous IL-2 conditioned medium did not appreciably increase the yield of killer cells generated in vitro. WBC cultured without f-sarc stimulators with or without IL-2 supplementation also generated killer (K) cells but at a low level. The killer cell population was composed of approximately 50% lymphocytes and 50% monocytes. Cats had K cells functional in antibody-dependent cell-mediated cytotoxicity against FeLV-coated chicken red blood cells but not against any FeLV-FeSV-infected transformed targets tested. Natural killer (NK) cell activity to any targets tested was not found. Although no evidence was found for K or NK cell activity against FeLV-FeSV-infected transformed cells, feline WBC were readily able to generate killer cells in vitro and it is probable that this cell-mediated immune potential is functionally important in vivo.

The immunobiology of human gliomas

The finding that glioma cells can express HLA-DR antigens and that their expression can be modulated by human recombinant γ-interferon should stimulate new ways to consider the immunotherapy of human gliomas. The presence of HLA-DR antigens might enhance the immunogenicity of the glioma cells. This hypothesis can be tested in vitro by mixed lymphocyte-tumor cell culture. Furthermore, the use of interleukin-2 may allow one to maintain for a relatively long term the proliferation of any cytotoxic T cell clone which should be obtained in vitro. It is even conceivable that some of these strategies could be used for adoptive immunotherapy. Since the present treatment modalities, in particular chemotherapy, have failed to improve the prognosis of malignant gliomas, it is of the utmost importance to investigate new forms of therapy.

Inhibition of proliferation without affecting the generation of cytotoxicity in the human mixed lymphocyte reaction

Phosphoramide mustard (PM) is considered to be the major tumoricidal metabolite of cyclophosphamide in vivo. The effects of this metabolite in vitro on several immune functions of human lymphocytes have been investigated. Very low concentrations (10 −7 to 10 −7 M) of PM added to lymphocyte cultures inhibited proliferation of the lymphocytes in response to mitogens and alloantigens. At these concentrations, inhibition of proliferation appeared to be due to a direct action of PM on the proliferative cells. Thus, concanavalin A-stimulated lymphocytes still acquired IL-2 receptors (Tac antigen) normally in the presence of PM (10 −6 to 10 −9 M). Only exceedingly high concentrations of PM (10 −5 M or greater) prevented the acquisition of Tac antigen. Similarly, the inhibition of proliferation was probably not related to endogenous IL-2 levels: addition of exogenous IL-2 to PM-containing cultures did not result in any restoration of proliferation. Further evidence that PM directly affected proliferative cells was that low concentrations of PM inhibited the proliferation of T cells continuously growing in IL-2. The exposure time to PM necessary for inhibition was essentially identical to those for lymphoproliferative responses to mitogens and alloantigens. Paradoxically, however, the generation of cytotoxic lymphocytes in mixed lymphocyte reactions (MLRs) and mixed lymphocyte tumor cell cultures (MLTCs) was very resistant to PM. In parallel MLRs and MLTCs the cytotoxic responses were resistant to approximately 1000-fold more PM than were the proliferative responses. Only at 10 −5 M PM were these inhibited. These data suggest that clonal expansion of cytotoxic lymphocytes or their precursors by proliferation is not an absolute requirement for the generation of cytolytic activity.

Generation of Human Cytotoxic T Lymphocytes Against Autologous Solid Tumors by Autologous Mixed Lymphocyte Tumor Cell Culture with T Cell Growth Factor

Autologous mixed lymphocyte tumor cell cultures (MLTC) generated cytotoxicity against autologous tumors in 5 out of 15 (33%) patients with head and neck cancer. Further cultivation of MLTC-activated lymphocytes with T cell growth factor (TCGF) resulted not only in the propagation of cytotoxic T lymphocytes (CTL) and an increase of cytotoxicity against autologous tumors, but also in the induction of killer cells against allogeneic tumor cells. The results of crisscross tests using fresh tumor cells from 17 donors and lymphocytes from 10 donors indicate that cultivation of MLTC-activated lymphocytes with TCGF generated killer cells cytotoxic for allogeneic tumors in most cases, but not for autologous or allogeneic phytohemagglutinin-induced lymphoblasts. Further, the results of a cold target inhibition test undertaken in an autologous tumor killing system suggest that at least 2 different subsets, specifically cytotoxic for autologous tumors and cytotoxic for both autologous and allogeneic tumors, were developed in the CTL induced by autologous MLTC followed by cultivation with TCGF. The phenotypes of the effector cells were shown to be OKT3+, Leu2a+, OKT8+, OKM1-, and Leu7- by blocking assay using complement and monoclonal antibody against the T cell surface marker.

Methods for amplifying the induction and expression of cytotoxic response in vitro to syngeneic and autologous freshly-isolated solid tumors of mice.

Spontaneously arising tumors are frequently poorly immunogenic and exhibit a limited capacity to induce cytotoxic effector lymphocytes. In the present study, various approaches have been used to amplify the induction and expression of cytotoxic responses in vitro toward freshly isolated, autologous, and syngeneic solid neoplasms of spontaneous origin in mice. Cytotoxic lymphocytes were generated in one-way mixed lymphocyte-tumor cell cultures (MLTC) consisting of splenocytes or lymph node cells from normal and from tumor-bearing mice co-cultured with inactivated tumor cells. Optimal culture conditions have been established for the number of responder (R) cells, the method of inactivation of the stimulating (S) tumor cells, the responder/stimulator (R/S) cell ratio, and the duration of sensitization. Under optimal sensitization conditions only weak cytotoxic responses, as measured by the 51Cr-release assay, were generated. The antitumor cytotoxic activity could be augmented 2- to 12-fold by using each of the following procedures: (a) addition of crude or of partially purified interleukin-2 (IL-2) to the sensitization cultures; (b) depletion of nylon-adherent cells from the responding cell population; (c) enrichment of large lymphoblasts from the sensitized effector cell population by Percoll density gradient; and (d) treatment of mice donating the responder lymphocytes with low doses of either cyclophosphamide, adriamycin, or indomethacin. Although the highly reactive effector cells generated under the improved conditions also reacted appreciably with unrelated tumor target cells, only low levels of cytotoxicity could be demonstrated against normal target cells. The antitumor cytotoxic cells in sensitized splenocyte cultures were exclusively Thy1+, Lyt1-2+, whereas in lymph node cell cultures some cytotoxicity was also exerted by Thy1+, Lyt1+2+ cells.

In vitro elicitation of cytotoxic response against a nonimmunogenic murine tumor by allosensitization.

The murine lymphoma (thymoma) PIR-2 of C57BL/6 origin, primarily induced in our laboratory by fractionated X-ray irradiation, has been shown to be nonimmunogenic by its failure to immunize syngeneic mice in vivo or to evoke a cytotoxic response in primary mixed lymphocyte-tumor cell cultures (MLTC) in vitro. We were able, however, to demonstrate the existence of anti-PIR-2 cytotoxic cells among allogeneic-primed C57BL/6 responding lymphocytes using the technique of limiting dilution cultures (LDC). The frequency of anti-PIR-2 cytotoxic cells among C57BL/6 lymphocytes sensitized against BALB/c splenocytes in mixed leukocyte culture (MLC) was 1/20 to 1/40, and the cytotoxic activity of positive LDC wells against PIR-2 reached 60% as determined by a 4-h 51Cr-release assay. The frequency of anti-PIR-2 cytotoxic cells could be increased two- to 10-fold (up to 1/4) by removing nylon-wool-adherent cells from the primed cell population and/or by enriching the primed lymphoblast population on a Percoll density gradient. Anti-PIR-2 cytotoxic cells were found to be Thy1+; Lyt1-2+ cells. Clones isolated from the LDC wells manifested strong cytotoxic activity toward PIR-2 cells and the stimulating BALB/c splenocytes but not against other H-2b tumor lines or C57BL/6 splenocytes. We suggest that the procedure of allostimulation in MLC-LDC is an effective in vitro means of generating highly reactive cytotoxic cells against poorly immunogenic neoplasms.

Induction of NKCF-like activity in mixed lymphocyte-tumor cell culture: direct involvement of mycoplasma infection of tumor cells.

Co-culture of CBA/J spleen cells and certain lines of YAC-1 stimulators resulted in the appearance of NKCF-like activity in 24- to 48-hr supernatants. Numerous other in vitro cell lines were effective stimulators of this splenic cytotoxic factor (SCF). The cells participating in SCF production were absent from normal thymocytes and were present in BALB/c nu/nu spleen, were nonadherent, asialo GM1+, and bore low levels of Thy-1.2. SCF could mediate lysis of certain NK-sensitive tumor targets in an 18-hr 51Cr-release assay. However, the induction of SCF was not correlated with the ability of a particular cell line to be lysed by NK cells, but showed an absolute correlation with the presence of mycoplasma contamination in cultured tumor cell lines. Mycoplasma negative cell lines, including an uninfected but NK-sensitive subline of YAC-1, were unable to induce SCF. Decontamination of mycoplasma-infected lines with antibiotics or by passage through syngeneic mice abrogated the ability of infected tumor cells to stimulate SCF. The ability to induce SCF could be restored by reinfection with mycoplasma. Tumor cell-free supernatants from contaminated cultures were mitogenic for CBA spleen cells and could themselves induce SCF activity in spleen cell supernatants. SCF production and the agent responsible could be removed by passing such supernatants through 0.1-micron filters. The organism apparently responsible for SCF induction from CBA spleen cells was typed and found to be Mycoplasma orale, a nonfermentative, arginine-dependent, common tissue culture contaminant. About 50 to 60% of SCF activity could be removed by 0.1-micron filters, suggesting that SCF is composed of two components: mycoplasma organisms themselves and a soluble cytotoxic factor produced in response to mycoplasma.

Autologous Mixed Lymphocyte Tumer Cell Culture in Patients With Renal Cell Carcinoma

Cell-mediated immunity was studied by measurement oflymphocyte response to autologous tumor cells in 19 surgically treated patients with histologically proved (mixed lymphocyte tumor cell culture) renal cell carcinoma. Tumor stage was low in 9 patients and high in 10, while grade was low in 11 and high in 8. Of 8 patients in whom a positive lymphocyte response was detected 6 had high and 2 had low stage tumors (p less than 0.05), while the grade of disease was low in 7 and high in l (p less than 0.05). Furthermore, the more advanced and undifferentiated the tumor the more significant the decrease in lymphocyte response less than 0.05). Lymphocyte response was positive in 5 of 8 patients with low stage and low grade tumors but negative in 7 with-high stage and high grade disease. However, no correlation between the lymphocyte response and the degree of microscopic lymphocytic infiltration in and around the tumor was found. This study confirms that the specific immunological defense mechanism of patients with renal cell carcinoma against the tumors remains well at an earlier stage of tumor development, especially in cases with well differentiated malignancy, and showed attenuation in parallel with pathological spread or in poorly differentiated tumors.

Generation of human cytotoxic T lymphocytes against fresh autologous and allogeneic solid tumors by mixed lymphocyte tumor cell culture with T cell growth factor.

Autologous mixed lymphocyte tumor cell culture (MLTC) induced cytotoxic lymphocytes against autologous tumor cells in 4 out of 14 donors (29%). Further cultivation of MLTC-activated lymphocytes with T cell growth factor (TCGF) resulted not only in the propagation of cytotoxic T lymphocytes (CTL) and an increase of cytotoxicity against autologous tumors, but also in the induction of killer cells against allogeneic tumor cells. Briefly, the results of crisscross tests using fresh tumor cells from 17 donors and lymphocytes from 10 donors indicate that cultivation of MLTC-activated lymphocytes with TCGF generated killer cells against allogeneic tumor cells in most cases, but not against autologous or allogeneic phytohemagglutinin-induced lymphoblasts. These effector cells were mainly OKT3+, OKT8+, OKM1- and Leu7-. Further, the results of cold target inhibition tests undertaken in an autologous tumor killing system suggest that at least 2 different subsets, specifically cytotoxic for autologous tumors and cytotoxic for both autologous and allogeneic tumors, were developed in the CTL induced by autologous MLTC followed by cultivation with TCGF.