A colony inhibition (CI) technique for demonstration of tumor cell destruction by lymphoid cells in vitro

The role of regulatory T lymphocytes in immune control of MC-2 fibrosarcoma

The role of T regulatory lymphocytes (T_reg) particularly in cancer is well known. The goal of the present study was to determine the contribution of these lymphocytes in the regulation of anti-tumor immunity of CBA/HZgr mice against MC-2 fibrosarcoma (4^th generation of methylcholanthrene induced tumor). The levels of T lymphocytes (CD4+, CD8+ and CD4+CD25+) were determined 8 and 20 days after tumor transplantation. Further, the role of CD4+CD25+ (T_regs) in tumor-host interaction was evaluated in vitro and in vivo by using specific monoclonal antibodies. We found that splenocytes of both control and T_reg depleted tumor bearing mice strongly but differently inhibited growth of tumor cells in vitro. While splenocytes of untreated mice exhibited significant decrease of this activity (from 74.4% to 62.6% and 32.95%), the splenocytes of T_reg depleted mice showed increase of this activity (from 79.5% to 84.3% and 86.2%) from day 6 to day 13 and day 21 after tumor grafting, respectively. Further, upon i.v. injecting specific monoclonal anti-T_reg antibody tumor immediately prior to tumor cell intracutaneous transplantation, the tumor was rejected after initial growth. In treated mice, the incidence of T_reg cells was very low initially, reaching normal values two weeks later. These animals were shown to be resistant to tumor transplantation four months later.

From the Hellstrom paradox toward cancer cure

Several decades ago we published some of the first papers showing that both murine and human cancers are recognized in vitro as immunologically foreign and that this is the case also in the presence of a growing tumor. The latter situation, sometimes referred to as the Hellstrom paradox, implies that the tumor is protected in vivo by a highly immunosuppressive environment. After many disappointments, the discovery that tumor-related immunosuppression can be counteracted by administrating monoclonal antibodies (mAbs) to checkpoint inhibitors such as CTLA-4, PD-1, and PD-L1 is now revolutionizing cancer therapy. Over the past several years we have applied mouse models in attempts to further improve the ability of such mAbs to cause long-term complete tumor rejection. This review is focused on that work and emphasizes that successful immunotherapy is associated with a shift from a tumor-promoting Th2 inflammation to a tumor-inhibiting Th1 response.

Cell-mediated autophagy promotes cancer cell survival

Immune effector cells integrate signals that define the nature and magnitude of the subsequent response. Experimental measures for immune cell-mediated lysis of tumors or virally infected targets rely on average responses of permeability or apoptotic changes within a population of targets. Here, we examined individual target cells following interaction with lymphoid effectors. We found that human peripheral blood lymphocytes not only provide lytic signals but also promote autophagy in the remaining cells. At high effector-to-target ratios, autophagy was induced in several human tumors, as assessed by induction of LC3 puncta and diminished p62. Natural killer cells are a primary mediator of this process. In addition, target cell autophagy was enhanced by provision of interleukin (IL)-2, whereas IL-10 attenuated this effect, and cell-to-cell contact strongly enhanced lymphocyte-mediated autophagy. Although IFN-γ can induce autophagy in target cells, IFN-α acted directly on the targets or in concert with lymphocytes to diminish target autophagy in some cell types. Importantly, cell-mediated autophagy promoted resistance from treatment modalities designed to eradicate tumor cells. Our findings therefore show that the lymphocyte-induced cell-mediated autophagy promotes cancer cell survival and may represent an important target for development of novel therapies.

Sensitivity of B16 melanoma sublines to lymphokine-activated killer cells as determined by 51Cr-release and clonogenic assays

The aim of this study was to compare the differential sensitivities of B16 melanoma sublines to LAK cells by means of the standard 51Cr release assay and a clonogenic assay, which measures both cell survival and proliferation. LAK cells, generated after 4 days incubation with 150 international units (IU)/ml of interleukin-2 (IL-2), showed both cytolytic and anti-proliferative activities against B16 targets. Using an 18 h 51Cr release assay, murine LAK cells showed the highest cytolytic activity against B16 parental cells compared to B16-F1, B16-F10, B16-FLR and B16-BL6 sublines at effector/target (E/T) ratios ranging from 6/1 to 100/1. Purified adherent LAK (A-LAK) cells showed greater cytolytic activity against B16 parental cells and other B16 sublines compared to LAK cells, but otherwise the pattern of reactivity was similar. Using a clonogenic assay, the surviving fraction of B16 parental cells co-cultivated with LAK cells decreased to 0 at an E/T ratio of 50/1, while a 400/1 ratio was required to achieve a similar reduction of B16-F1, B16-F10, B16-FLR, and B16-BL6 sublines. No differences in subline sensitivity were seen with the 51Cr release assay, but these were observed using the clonogenic assay. An inverse linear relationship existed between % surviving fraction, as determined by the clonogenic assay, and cytolytic activity, as determined by the 51Cr release assay. Our data indicate that the clonogenic assay can detect differences in target cell sensitivity that otherwise are undetectable by the standard 51Cr release assay. The clonogenic assay may prove useful in delineating the long-term anti-adherent and anti-proliferative properties of effector cells from their cytolytic activity.

An analysis of the SCM test in cancer diagnosis

A new diagnostic blood test for cancer, the Structuredness of Cytoplasmic Matrix (SCM) test, has been widely claimed to distinguish between normal healthy controls and patients with malignant disease. It has also been claimed that the test distinguishes between patients with nonmalignant conditions and patients with cancer. Furthermore, it has been stated that the test makes it possible to identify the specific type of tumor in each case. In view of the importance of these claims, the study was repeated under identical laboratory conditions. Six hundred and twenty-one blood samples from controls and various groups of patients were processed in an exhaustive investigation. Four objectives were set: (1) to apply the test to a group of normal healthy individuals; (2) to apply the test to a group of patients with nonmalignant disease; (3) to apply the test to a group of cancer patients; and (4) to attempt to relate the degree of positivity of the test, if any, to the extent or stage of the tumor. Using the results described, confirmation of any of the above claims was not achieved. From this study, it is concluded that the test is of no clinical value.

Red blood cells coated with tumor cell extracts as targets in 51Cr release assays

Sheep red-blood cells were coated with tumor cell antigens prepared by extractions with 3M KCl. The coated cells were labelled with 51Cr and used as targets in immuno-assays. The technique was found suitable for complement-mediated as well as antibody-dependent cell-mediated reactions, and it offers several applications for use in tumor immunology.

Surveillance of human mitral valve cells by autochthonous lymphocytes, in vitro

Analysis of a time-lapse film of cultured human mitral valve endothelium containing autochthonous lymphocytes reveals details of a pattern of interaction suggesting a previously undescribed type of cellular surveillance. Highly mobile lymphocytes rapidly approach individual endothelial cells, slowly circumnavigate the nuclear region, and rapidly move away to repeat this behavior on adjacent cells during the 1-month culture period.

Relationship of in vitro immune responses to Epstein-Barr herpesvirus and severity of infectious mononucleosis

Immune responses to Epstein-Barr herpesvirus (EBV) and EBV-related antigens were studied serially in 18 patients with heterophil antibody-positive infectious mononucleosis and in 18 control subjects. Enhanced cellular immune responses to EBV particles and to EBV intracellular soluble antigens were found in the patients at convalescence, suggesting that the development of specific cellular immune responses was associated with apparent control of the virus infection. In addition, a correlation between severity of disease and specific cellular immune response was found. Patients with severe clinical signs were found to have a more active cellular immune response to EBV intracellular soluble antigens early in the infection compared with patients with mild disease. This suggests that an increased immune reactivity to intracellular antigens during the early part of the illness is related to the severity of clinical manifestations in infectious mononucleosis. Serum antibody to viral capsid antigen and early antigen was not related to the severity of clinical disease.

Susceptibility of Ad12-transformed S (+) and S (-) mouse cells to cell-mediated immunity in vitro

Adenovirus type 12 (Ad12)-transformed mouse cells were examined for their susceptibility to cell-mediated immunity in vitro, with respect to the activity of the virus-specific surface (S) antigen in the cells. A transformed cell line, C57AT1, was established from embryonic cells of C57BL/6 mice by Ad12 infection. In fluorescent antibody tests, the transformed cells were positive for the S antigen when the cells were maintained as cultures, whereas when the cells were grown as tumors in animals they became negative for the antigen (referred to as S(+) and S(-) cells, respectively). These S(+) and S(-) cells were subjected to the 51Cr-release test for cell lysis by immune spleen cells (ISC) raised in syngeneic mice by Ad12 infection. When the S(+) cells at various passage levels were exposed to ISC, all of them were lysed extensively and to a similar extent irrespective of their passage history. In contrast, the S(-) cells were consistently refractory to the action of ISC. In addition, the cytotoxic action of ISC was markedly impeded by pretreating the S(+) cells with antiserum to the S antigen, or the ISC with anti-Thy-1,2 serum plus complement. Taken these findings together, the S(+) cells were assumed to be injured by ISC through direct interaction of the S antigen with T-lymphocytes.

Microcytotoxicity assay for cell-mediated immunity enumerating residual target number by 86Rb

Lymphocyte-mediated lysis of target cells grown as monolayers in microtiter wells is readily quantitated by an assay measuring the 86Rb incorporated after attaining isotopic equilibrium. Lysis of fibroblasts by allogeneic lymphocytes sensitized by skin grafts and of tumor cells by syngeneic spleen cells sensitized by intraperitoneal tumor inoculation were readily detected. Weakly cytolytic lymphocyte populations can be assayed by increasing incubation times to 48 h or longer. A potential problem, 86Rb incorporation by lymphocytes sticking to residual target cells, was controlled by comparing 86Rb incorporation by targets incubated with non-immune lymphocytes. Results by 86Rb incorporation were identical to those determined by microscopic counting or 51Cr release. 86Rb incorporation assays should be considered as an alternate to 51Cr release techniques, especially in those experimental systems where the cytolytic potential of a lymphocyte population is so low that lysis can be detected only after long incubation times and/or when the spontaneous release of 51Cr is prohibitively high.

Unspecific cellular immunity before therapy in patients with squamous cell carcinoma of head and neck

An introduction to the role of lymphocytes in immunological reactions is given. Two fundamental categories of immunological response are described which are mediated by two distinct subpopulations of lymphocytes: B-lymphocytes are responsible for humoral immune reactions and T-lymphocytes are involved in cell-mediated immunity. Information is given on the role of the immune system in generation of anti-tumour activities and of mechanisms leading to an acceleration of tumour growth. Several pathways of cytotoxic and blocking reactions against target cells are mentioned. Furthermore, methods are described for monitoring the non-specific immune reactivity of the host. These nonspecific cellular immune responses in 30 patients with squamous cell carcinoma of the head and neck were compared with those in 30 healthy controls. Assays were performed in vitro to evaluate the blastogenic response of lymphocytes to the mitogens PHA (phytohaemagglutinin) and PWM (pokeweed mitogen) and to quantify T-rosetteforming lymphocytes in the peripheral blood. The in vivo assays used were the delayed cutaneous hypersensitivity reaction to the primary stimulus of DNCB (dinitro-chloro-benzene) and the recall reaction to PPD (purified protein derivate). The carcinoma patients demonstrated significant impairment of lymphocyte blastogenesis reactions to PHA but not to PWM. The percentage and absolute counts of T-rosettes was significantly reduced in cancer patients compared with normal controls. Skin test reactivity to de-novo sensitation with DNCB was significantly abnormal in patients with head and neck cancer. However, delayed type hypersensitivity evaluated with PPD (recall antigen) was not significantly reduced. After subdividing the cancer patients according to their clinical stage of disease and subsequent analysis, they showed no correlation between clinical stage and immune reactivity. These data indicate that PHA induced lymphocyte blastogenesis, enumeration of T-rosette levels and evaluation of delayed hypersensitivity reaction to DNCB are potentially useful for the study of squamous cell carcinoma of head and neck to monitor effects of tumour treatment and perhaps to evaluate a correlation between immunocompetence and prognosis.

Stage IVS neuroblastoma

This is a review of the findings in 10 cases of stage IVS neuroblastoma, that have been observed in the First Surgical Department of Hokkaido University Hospital. The patients under the age of 1 yr in stage IVS neuroblastoma have a favorable prognosis; the survival rate was 70%. The regressions were histologically confirmed as maturation of the neuroblastoma cells to ganglioma cells. The lymphocyte counts and T-cell function were well maintained in the surviving patients but both were markedly reduced in the patients who later died. The treatment should be conservative so that immune mechanisms are not inhibited and should be withheld until respiratory failure or progressive signs toward stage IV are identified.

A simplified isotope release assay for cell-mediated cytotoxicity against anchorage dependent target cells

An assay for cell-mediated cytotoxicity has been developed in which anchorage-dependent target cells are cultured on small plastic beads in suspension. Confluent target cells on the beads are handled by methods appropriate to suspension-grown cells and labelled with chromium-51, iodine-125 and [3H]proline. Fetal human lung fibroblasts and HeLa cells were used as targets in model experiments measuring human natural killer cell activity. In 20 h experiments, chromium-51 was the most suitable isotope. In 40 h experiments, [3H]proline release assay was superior to chromium-51 and iodine-125 assays. The bead cytotoxicity assay offers a rapid and simple isotope release technique for anchorage dependent cells because no trypsinization and re-seeding of target cells is needed.

Inhibition of clone formation as an assay for T cell-mediated cytotoxicity: short-term kinetics and comparison with 51Cr release

The short-term kinetics of T cell-mediated cytotoxicity was investigated using a cloning inhibition assay. Murine cytotoxic thymus-derived lymphocytes (CTL) generated in vitro in mixed leukocyte cultures (MLC), were incubated for various periods of time at 37 degrees C with allogeneic mastocytoma target cells. The mixtures were then plated in soft agar, and mastocytoma clone formation was assessed after 5-7 days incubation. Using this technique, it was demonstrated that events leading to the loss of cloning ability could be detected after 1-3 min incubation at 37 degrees C, and after 20-30 min, 95% of the clone forming cells had been inactivated. When these results were compared directly with those obtained using the conventional 51Cr-release assay, it was found that the events leading to loss of cloning ability occurred more rapidly than indicated by the isotope assay. However, a modification of the 51Cr-release assay involving EDTA addition, gave comparable results to the cloning inhibition assay. These results raise the possibility that the events leading to 51Cr-release of tumor target cells may be related in time to those leading to the loss of cloning ability.

Immune evaluation with skin testing. A study of testicular, prostatic, and bladder neoplasms

Fifty patients with testicular carcinoma, 45 with prostatic neoplasm, 84 with bladder carcinoma, and 13 with benign bladder papilloma were evaluated for skin reactivity to DNCB and other intradermal antigens. Correlation between pathologic staging and skin-test reactivity was sought. Reaction to DNCB among patients with testis tumors was more significantly depressed by chemotherapy than by the extent of retroperitoneal or distant metastatic disease indicating that skin testing as a means of following the course of disease or of predicting survival may be limited by alterations caused by chemotherapy. DNCB reactivity did not correlate with the prognosis for the different stages of disease, but follow-up studies of individual patient survival are needed for substantiation. Depression of DNCB reactivity exists among patients with prostatic carcinoma whether the disease is localized or widely metastatic. Only lengthy follow-up will determine if there is any correlation of reactivity with survival in individual patients. DNCB reactivity among patients with bladder tumors shows progressive reduction with increasing stage disease and lends support to the evidence suggesting immune deficiency in patients with bladder neoplasm.

Cellular immunity in mammary cancer patients as measured by the leukocyte migration test (LMT). A follow-up study

In 58 cases of mammary cancer treated by surgery the leukocyte migration test (LMT) has been applied to the study of cellular immunity using homogenate from autochthonous and homologous tumors as antigens. A positive test, i.e. inhibition of migration by antigen, was observed in 52 patients from 1 day up to 40 days after surgery. Six patients were negative. There was extensive immunological cross-reactivity among mammary cancer in that a positive test was also obtained with homogenate from homologous mammary tumors. Generally, antigens from other tumors did not react. The test was also negative when the leukocytes were derived from healthy persons. Sera from mammary cancer patients abrogated the inhibitory effect of tumor antigen. The disappearance of positivity about 40 days after surgery and its reappearance during the metastatic process indicates that the positive LMT is associated with progressive disease.

A long-term 51chromium assay for in vitro cell-mediated tumor immunity. Correlation with simultaneously performed microplate assays

In vitro assays of cell-mediated tumor immunity utilizing 51Chromium (51Cr) labelling of cultured adherent solid tumor cells were designed which allowed an effector cell/target cell incubation time of 48 h without overriding spontaneous 51Cr release. In a series of 16 consecutive experiments, blood lymphocytes from healthy human donors, from patients with tumors unrelated to the cultural tumor target cells, and from colon carcinoma and melanoma patients were tested for their cytotoxic effects on various target cell pairs, human colon carcinoma, melanoma, or skin fibroblasts. The same reagents were used in simultaneously performed microplate and 51Cr assays. Results obtained by visual counting of microplate tests and by 24-h assays of 51Cr release or 51Cr retention correlated in 20/25 effector-cell/target-cell combinations. In a series of six consecutive experiments, lymph-node cells from untreated Wistar/Furth rats, and rats bearing either chemically-induced colon carcinoma NG-W1 or polyoma virus-induced sarcoma P-W13 were tested for their cytotoxicity on syngeneic rat colon carcinoma and sarcoma target cells. Criss-cross type experiments were performed by microplate and 15Cr techniques done in parallel. Results obtained by visual counting of microplate tests and by 48 h assays of 51Cr release or 51Cr retention correlated in 15/18 effector-cell/target-cell combinations.

[Mitogenic activity of melanoma extracts in leucocyte cultures (author's transl)]

From a mixed cell suspension of five primary melanomas an aqueous sterile extract was made and added to homologue leucocyte cultures of eight melanoma patients and seven controls. The extract had a blastogenic and mitogenic effect in all cultures. There was no significant difference between the responses of patients and controls. In experiments with an equally prepared extract of normal skin, added to homologue leucocyte cultures of nine persons, none but one had a positive reaction. This indicates, that the motigenic principle of the melanoma extract is not related to the histocompatibility antigen nor caused by chemical or bacterial contamination of the primary cell suspensions. It seems to be derived from the cytoplasmic fraction of melanoma cells. Other experiments to solve the problem were impossible because of lack of material. There are several reports in the literature which by using different methods indicate, that there might be an immunological reaction to melanoma associated principles in healthy persons, too.

51Cr release microassay for measuring cell-mediated immunity in chickens

A microcytotoxic assay, based on the release of 51Cr from chicken erythrocytes by sensitized chicken lymphoid cells in the presence of the specific antigen, purified protein derivative (PPD), is described. The percentage of antigen-specific lysis was dependent on the lymphoid cell concentration, antigen concentration, time of incubation, and incubation temperature. Maximum antigen-specific lysis of nonspecific target cells was induced with a spleen-to-target cell ratio of 100:1 and with a peripheral blood lymphoid-to-target cell ratio of 1,000:1 in the presence of 100 mug of PPD per ml over a 20-h incubation period. As the concentration of PPD was increased from 25 to 200 mug/ml the specific lysis that incubation for 20 h. Incubation at 41 C produced significantly higher (P smaller than 0.05) antigen-specific cytotoxicity than incubation at 37 C.

Leukocyte mediated cytotoxicity of chemically induced rat salivary gland neoplasms

Chemically induced tumors of the rat submaxillary glands were tested for the presence of tumor antigens by in vitro leukocyte mediated cytotoxicity assays. Since it has been reported that the saliva of humans with oral cancer contains markedly elevated levels of secretory antibody, the rats' saliva specimens were also tested for blocking and/or potentiating "antibody" activity. The results indicate that saliva from tumor-bearing animals potentiated tumor cell killing if either the tumor cells or leukocytes were pretreated. The effect was much more marked when tumor cells were pretreated. Furthermore, the addition of saliva to tumor cells imparted an immunologic cross reactivity which was not present with untreated tumor cells. Control saliva occasionally produced a similar effect, but not as consistently or with the potency of saliva from tumor-bearing animals. Heat inactivation did not abrogate this potentiation. It is inferred that this may indicate a new system of immunologic surveillance, i.e. arming or potentiation of leukocytes by soluble tumor antigens in glandular secretions.