Suppression of T cell-mediated immunity by tumor cells: immunogenicity versus immunosuppression and preliminary characterization of the suppressive factors

The clinical study on treatment of CD19-directed chimeric antigen receptor-modified T cells in a case of refractory Richter syndrome

Richter syndrome (RS) indicates the transformation of chronic lymphocytic leukemia (CLL) into an aggressive lymphoma (mostly DLBCL). Richter syndrome is a rare complication with an aggressive clinical course, bearing an unfavorable prognosis. Currently, there is no effective treatment for it. As a novel cellular‐based immune therapy, chimeric antigen receptor‐modified T (CART) cells treatment is gradually used in treating hematological malignancies, especially in CD19⁺ B‐cell malignancy. Therefore, CD19‐directed chimeric antigen receptor‐modified T cells (CART‐19) treatment is promising to be used as a new method for RS patients. In our study, one RS patient expressing high level of CD19 molecule was enrolled in clinical trial; he has received a series of treatments but did not achieve a satisfactory therapeutic effect. The patient totally received 3.55 × 10⁸ autologous CART‐19 cells infusion. After CART‐19 infusion, the mainly clinical side effect was repeated fever. The maximal duration period was 24 days and the highest temperature was 40.1°C. Pancytopenia and significantly serum cytokines level rise were observed, including IFN‐γ, IL‐6, and IL‐10. Before discharge, the level of cytokines reduced to normal levels. In addition, we detected the serum biochemical indices as like K⁺, Ca²⁺, creatinine, and glutamic‐pyruvic transaminase, all of these indices were normal. This showed that there was no tumor necrosis syndrome after treatment. The proportion of B cells in patient's peripheral blood decreased from 72% to 40.2% after infusion, co‐occurring with reduction in lymph nodes and hematopoietic reconstitution. Based on the recent revolution in the therapeutic landscape for hematological malignancies including B‐cell lymphomas, CART‐CD19 cell therapy as a new therapeutic option for RS might be available in the coming years. It aims to reduce patient's tumor burden, prolong their survival time, and provide opportunities for other sequential therapy such as chemotherapy and bone marrow transplantation.

Anti-tumor effects of (1→3)-β-d-glucan from Saccharomyces cerevisiae in S180 tumor-bearing mice

(1→3)-β-d-Glucan from Saccharomyces cerevisiae is a typical polysaccharide with various biological effects and is considered a candidate for the prevention and treatment of cancer in vitro. Research into the function of (1→3)-β-d-glucan in tumor-bearing animals in vivo, however, is limited. Here, we investigated the effects of (1→3)-β-d-glucan from S. cerevisiae on S180 tumor-bearing mice and on the immunity of the tumor-bearing host. The molecular mechanisms underlying the observed effects were investigated. (1→3)-β-d-Glucan was shown to exert anti-tumor effects without toxicity in normal mouse cells. The volume and weight of S180 tumors decreased dramatically following treatment with (1→3)-β-d-glucan, and treatment with the polysaccharide was furthermore shown to increase the tumor inhibition rate in a dose-dependent manner. Spleen index, T lymphocyte subsets (CD₄ and CD₈), as well as interleukins (IL)-2, (IL-2, IL-6), and tumor necrosis factor-α were assayed to detect the immunoregulatory and anti-tumor effects after (1→3)-β-d-glucan intragastrical administration. (1→3)-β-d-Glucan was shown to significantly potentiate the mouse immune responses by, among other effects, decreasing the ratio of CD₄ to CD₈. The expression levels of IL-2, IL-6, and TNF-α were also significantly increased by (1→3)-β-d-glucan. These results suggest that (1→3)-β-d-glucan enhances the host's immune function during the tumor inhibition process. S180 tumor cells treated with (1→3)-β-d-glucan also exhibited significant apoptotic characteristics. (1→3)-β-d-glucan increased the ratio of Bax to Bcl-2 at the translation level by up-regulating Bax expression and down-regulating Bcl-2 expression, resulting in the initiation of cell apoptosis in S180 tumor-bearing mice. Taken together, these results indicate that the anti-tumor effects exerted by (1→3)-β-d-glucan may be attributed to the polysaccharide's immunostimulating properties and apoptosis-inducing features. Further investigation into these properties and their associated mechanisms will contribute to the development of potent polysaccharide-based anti-tumor agents.

Anti-hepatoma activity and mechanism of corn silk polysaccharides in H22 tumor-bearing mice

Corn silk is a well known traditional Chinese herbal medicine and corn silk polysaccharides (CSP) possess multiple pharmacological activities. However, the antitumor effect of CSP on hepatocarcinoma has not been studied. This study aimed to investigate the effects of CSP on tumor growth and immune functions in H22 hepatocarcinoma tumor-bearing mice. The results demonstrated that CSP could not only inhibit the tumor growth, but also extended the survival time of H22 tumor-bearing mice. Besides, CSP administration could increase the body weight, peripheral white blood cells (WBC) count, thymus index and spleen index of H22 tumor-bearing mice. Furthermore, the production of serum cytokines in H22 tumor-bearing mice, such as IL-2, IL-6 and TNF-α, was enhanced by CSP treatment. In addition, no toxicological effects were observed on hepatic function and renal function in CSP-treated mice transplanted H22 tumor cells. In summary, this experimental finding indicated that CSP could elevate the immune functions in H22 tumor-bearing mice to enhance its antitumor activity and CSP seems to be a safe and effective agent for the treatment of hepatocellular carcinoma.

Lung cancer with gastrointestinal metastasis - review of theories of metastasis with three rare case descriptions

Approximately 1 in 14 men and women during their lifetime will be diagnosed with lung cancer, which is the leading cause of cancer-related mortality in the world. As of January 1, 2008, there were about 373,500 men and women living with lung cancer in the United States. Fewer than 60,000 of these are estimated to be alive by January 2013, reflecting a poor overall 5-year relative survival rate of under 16 %. With metastatic cancer, the overall 5-year survival is meager 4 %. On the other hand, the overall five-year survival is over 50 % when the cancer is still in the localized stage. However, unfortunately, more than half of cases of lung cancer are diagnosed at an advanced stage Howlader et al. (2010). Cancer metastasis, the single most critical prognostic factor, is still poorly understood and a highly complex phenomenon. The most common sites of lung cancer metastasis are the lymph nodes, liver, adrenals, brain and bones. The gastrointestinal (GI) tract is an exceptionally rare site of metastasis; with only a handful of cases reported in the literature Centeno et al. (Lung Cancer, 18: 101-105, 1997); Hirasaki et al. (World J Gastroenterol, 14: 5481-5483, 2008); Carr and Boulos (Br J Surg, 83: 647, 1996); Otera et al. (Eur Respir Rev, 19: 248-252, 2010); Antler et al. (Cancer, 49: 170-172, 1982); Fujiwara et al. (Gen Thorac Cardiovasc Surg, 59: 748-752, 2011); Stinchcombe et al. (J Clin Oncol, 24: 4939-4940, 2006); John et al. (J Postgrad Med, 48: 199-200, 2002); Carroll and Rajesh (Eur J Cardiothorac Surg, 19: 719-720, 2001); Brown et al. (Dis Colon Rectum, 23: 343-345, 1980). We report three cases of non-small cell (squamous cell) lung cancer with GI tract metastasis-two in the colon and one in the jejunum. Then we present a review of literature exploring various theories of metastasis, as an attempt to understand the reason of preferential tumor metastasis.

Modulation of prostaglandin activity, part 1: prostaglandin inhibition in the management of nonrheumatologic diseases: immunologic and hematologic aspects

Prostaglandins (PGs) are active biologic substances that are involved in a wide range of physiologic processes; when their production is out of balance, they are factors in the pathogenesis of illness. Modulation of PGs by inhibition or stimulation is promising for the management of various conditions. PG inhibitors are widely used to relieve pain and inflammation in patients with rheumatologic disease. Interest in the use of PG inhibitors to prevent cancer and cardiovascular events is growing. More than 27 y ago, investigators found that PG depresses antibody production in vivo; reduces serum iron, hemoglobin, and leukoid series in bone marrow during acute and chronic blood loss; reduces albumin during antigenic stimulation; suppresses hypercalcemia after bleeding; and reduces fasting blood sugar and hyperglycemia after ether anesthesia and bleeding. Chronic conditions that produce large quantities of PGs are associated with immunosuppression and secondary anemia. Investigators in the present study hypothesized (1) that the overproduction of PGs is responsible for immunosuppression and secondary anemia in conditions associated with increased PG synthesis, such as pathologic inflammation, malignancy, trauma, and injury, and (2) that PG inhibitors reverse immunosuppression and secondary anemia, thereby enhancing the immune response. This is supported by many reports that show the immunosuppressive effects of PGs and their role in the immunosuppression associated with pathologic inflammation, burns, trauma, and tumors. Inhibition of PGs can be achieved through the use of synthetic medicines and natural products. This article reviews the effects of PGs and inhibition of increased synthesis of PGs on the lymphoid system, hematologic indices, and bone marrow elements in trauma, injury, burns, and tumors. The Medline database (1966-2006) was used in this study. Investigators in the present study and others have provided evidence that shows the involvement of PGs in immunosuppression and secondary anemia, as well as the efficacy of inhibited overproduction of PGs in many pathologic conditions other than rheumatologic disease.

Impairment of T-cell functions with the progressive ascitic growth of a transplantable T-cell lymphoma of spontaneous origin

It has been observed that the progressive ascitic growth of a transplantable T-cell lymphoma of spontaneous origin, designated Dalton's lymphoma (DL), in a murine host induces inhibition of various immune responses and is associated with an involution of thymus accompanied by a massive depletion of the cortical region and alteration in the distribution of thymocytes caused by tumour serum-dependent induction of apoptosis with a decrease of CD4(+)CD8(+), CD4(+)CD8(-) and CD4(-)CD8(+) thymocytes. Here, we report that thymocytes of DL-bearing mice are defective in their proliferative ability and in their response to non-specific mitogenic stimulus in vitro. Also, antigen-specific T-cell proliferative ability representing the fundamental T(H) function declines under DL-bearing conditions and upon treatment with serum of DL-bearing mice. Moreover, a significant inhibition of T-cell cytolytic activity with a decreased ability to produce interferon gamma is shown by the T cells of DL-bearing mice and by the T cells treated with DL-ascitic fluid, DL-conditioned medium or serum of DL-bearing mice. Further, addition of interleukin-2 and anti-interleukin-10 to the cultures of thymocytes treated with serum of DL-bearing mice is found to inhibit the induction of apoptosis in thymocytes, a phenomenon associated with the progression of DL growth. Analysis of the results indicates an immune deviation with the predominance of a T(H2)-type response with the progression of tumour. We further discuss the possible mechanisms that may explain the observed tumour-induced diminution of T-cell immunity.

Reversal of multiple-site tumor cell-induced immunosuppression by specific cytokines and pharmacological agents

The present study explores a model for tumor cell-induced immunosuppression and reversal of suppression by cytokines and other pharmacological agents. To simulate tumor-cell-induced suppression, a panel of suppressor agents which included CsA (cyclosporin A), SSP (staurosporine), BSO (L-buthionine-[S,R]-sulfoximine) and PMA, and a panel of anti-suppressor agents which included IL-2, IL-4, GSH (glutathione) and amiloride, were tested. These suppressor/anti-suppressor agents acted differently on four specific sites of the immune arm that affected the alpha CD3-induced T cell proliferative and cytotoxic responses. They included (1) IL-2 production, (2) PKC-regulated cytolytic granule production, (3) GSH-regulated maturation of functional granules, and (4) granule exocytosis. When a single suppressor agent was used, all the suppressor agents tested in this study inhibited the generation of alpha CD3-induced activated killer cells (CD3-AK), whereas alpha CD3-induced proliferation was inhibited by CsA, BSO, and EL-4 tumor cells. Except for EL-4, suppression induced by a single suppressor agent could be corrected by an appropriate single anti-suppressor agent. Multiple suppressor agents induced profound suppression of CD3-AK response. In most cases, multiple anti-suppressor agents were required to correct the immune defects induced by multiple suppressor agents. Finally, EL-4 tumor-cell-induced immunosuppression could not be corrected by any single anti-suppressor agent tested, but a combination of IL-4, GSH and amiloride fully restored the CD3-AK response. These results suggest that tumor cells may induce multiple immune defects that require multiple anti-suppressor agents for correcting the defects to restore the host immunocompetence.

Suppression of cytotoxic T lymphocyte activity by gamma/delta T cells in tumor-bearing mice

Spleen cells derived from tumor-bearing mice prove useful for the elucidation of the mechanism determining how tumor cells evade cytotoxic T lymphocytes (CTL) in tumor-bearing hosts. Our data indicate that inactive CTL or precursor CTL specific for tumor antigens are present among lymphocytes of tumor-bearing mice. However, their activity is inhibited by a soluble factor produced by other cells present in the same source. Inhibition of the cytolytic reaction was also detected in the culture supernatant of spleen cells obtained from normal mice, precultured in the presence of tumor cell culture supernatant and interleukin-2 (IL-2). Cell-depletion and cell-purification studies let us conclude that cells that produced the CTL-inhibitory factor (CTL-IF) were gamma/delta T cells. The gamma/delta T cells that were activated in vivo in tumor bearers were able to produce CTL-IF after isolation and in vitro culture. Maximum activation of gamma/delta T cells was achieved by antigenic stimulation and by suppression of cells that interfered with the activation of gamma/delta T cells. CTL-IF, which was assayed by use of CTL clones, did not show antigen specificity. Inhibition depended on a relatively heat- and acid-stable, but alkali-labile molecule with a molecular mass of less than 10 kDa. The latter characteristics imply that CTL-IF does not resemble any of the known lymphokines produced by gamma/delta T cells. These observations emphasize the crucial role of the gamma/delta T cells in the escape of tumor cells from the attack of tumor-specific CTL.

Immunosuppression in murine renal cell carcinoma. II. Identification of responsible lymphoid cell phenotypes and examination of elimination of suppression

In our companion paper we have reported that cell-mediated immunity of mice bearing renal cell carcinoma is profoundly suppressed. The non-responsiveness of such animals was found to be attributable to Renca cells themselves and to splenic lymphoid cells that down-regulate other fully capable lymphoid cells. In this communication the lymphoid cell source of suppression within Renca-bearing mice has been explored with the aim of identifying phenotypes of the responsible cells, the manner by which suppression is mediated, and initial ways by which suppression may be eliminated. A plastic-adherent cell bearing the Thy1.2 surface marker as well as the Lyt1 and Lyt2 antigens has been found to operate, perhaps in conjunction with macrophages, to down-regulate lymphokine-activated killer (LAK) cell development for natural killer (NK) and non-NK targets that include Renca cells themselves. The splenic suppressor cells lost the capacity to suppress the NK response of normal recipient mice upon shallow irradiation (250 rad) prior to adoptive transfer. Spleen cells, presumably macrophages, from Renca-bearing mice were found to suppress the generation of LAK and NK cells in vitro by synthesizing prostaglandins. Indomethacin, a prostaglandin synthetase inhibitor, blocked the induction of suppression both in vitro and in vivo, suggesting the presence of endogenous prostaglandins in Renca-bearing mice. The suppression seen in Renca-bearing mice that derives from multiple sources and has been prevented by two separate methods has been discussed from the viewpoint of the inter-relatedness of the sources.

Antitumour effect of intratumoral injection of human recombinant interleukin-2 in patients with hepatocellular carcinoma: a preliminary report

Five hepatoma patients with small resectable tumour received an intratumoral injection of recombinant interleukin-2 (rIL-2) once weekly over 2-4 weeks (1.05 x 10(6)-3.6 x 10(6) U in total per patient). Tumour regressions of 32% and 57% were observed in two patients at day 42 after the first rIL-2 injection. No response was observed in two patients and disease progressed in one. Lymphokine-activated killer (LAK) activity was enhanced and Leu-11+ cells increased in the peripheral blood in the patients with 32% and 57% tumour regression after rIL-2 therapy. However, LAK activity, Leu-7+ cells were reduced in the patient who progressed. No consistent changes in Leu-2a+ cells and Leu-3a+ cells were demonstrated. In the three patients showing no response or 32% tumour regression, hepatic segments containing tumour were resected; histologically the tumour showed severe necrosis and lymphocytic infiltration in the patient with 32% tumour regression but mild or moderate changes in the other two. IL-2 mediated tumour killing can be induced in tumours by intratumoral injection of rIL-2, leading to tumour regression.

Partial purification of an immunosuppressive protein from a human tumor cell line and analysis of its relationship to transforming growth factor beta

The A673 human rhabdomyosarcoma cell line constitutively produces an acid-soluble, potent immunosuppressive factor (ISF), which inhibits T-cell proliferation. We have partially purified this factor from the culture supernatant of A673 cells by a sequence of acid extraction, gel filtration, cation exchange chromatography, and reverse-phase HPLC. Characterization studies indicate that ISF is similar or identical to transforming growth factor beta (TGF beta). ISF exhibits a molecular weight of 25 kDa in sodium dodecyl sulfate-polyacrylamide gels. ISF, like TGF beta, is a very basic protein (pI = 9.5) that is sensitive to reduction. Anti-TGF beta 1 antibodies completely block ISF activity in the thymocyte assay. Furthermore, ISF, like TGF beta, stimulated the anchorage-independent growth of normal rat kidney fibroblasts in soft agar.

Specific cytotoxic activity of T lymphocyte clones derived from a patient with gliosarcoma

Eleven lymphocyte clones were established from the peripheral blood lymphocytes of a patient with gliosarcoma by means of autologous tumor stimulation and the limiting-dilution technique with recombinant interleukin-2. Ten of the 11 clones were cytotoxic against the autologous tumor cell line GI-1. Seven of the 10 clones were also cytotoxic against allogeneic brain-tumor lines and HeLa cells, one clone was cytotoxic against several target cells, and two clones were specifically cytotoxic against GI-1 and allogeneic brain-tumor cells. One of the 11 clones was not cytotoxic against any target cells tested. Lymphokine-activated killer cells induced by recombinant interleukin-2 alone exhibited cytotoxic activity against all target tumor cells tested. Surface phenotypic analysis revealed that all lymphocyte clones expressed CD3 antigen, some expressed CD4 antigen, and others expressed CD8 antigen. These clones seemed to be antigen-specific cytotoxic T lymphocyte clones. Analysis with these antigen-specific cytotoxic T lymphocyte clones may be useful in the elucidation of tumor-specific or tumor-associated antigens on autologous tumor cells.

Suppressor T cells with histamine type II receptors in chickens bearing chemically induced fibrosarcomas

Immunity to a local (wing web) challenge with transplantable, chemically induced tumors, such as CHCT-NYU-4, can be transferred to histocompatible SC chickens with intravenously injected splenic T cells from tumor-immune chickens. Simultaneous iv injection of splenic T cells from chickens bearing progressively growing CHCT-NYU-4 prevents the expression of this adoptive systemic tumor immunity. The splenic suppressor T cells are B-L(Ia) positive and adhere to dishes coated with cimetidine-protein conjugate, suggesting that they bear type II histamine receptors (H2R). Intravenous injection of gamma-irradiated CHCT-NYU-4 cells 7 days prior to a local challenge with the same tumor promotes growth of a normally suboptimal tumor cell dose such that the incidence of progressive tumor growth is significantly increased. Concomitant treatment with the H2R antagonist, ranitidine, inhibits tumor growth of an optimal tumor dose challenge and promotes induction of tumor immunity. However, this drug cannot reverse the effect of iv injected tumor cells. Another drug with reported antisuppressor cell activity, cyclophosphamide (50 mg/kg), injected 1 day prior to challenge causes a transient inhibition of tumor growth. Injection of this drug on Day 7 does not have a significant effect by itself but, in combination with the Day-1 pretreatment, a significant inhibition of tumor growth by size and tumor incidence measurements is obtained. These results indicate that manipulation of immunity to transplantable fibrosarcomas in the chicken is possible with drugs acting on suppressor cells.

Generation of activated killer cells in tumor-bearing hosts

Activated killer (AK) cells were generated in spleen-cell cultures derived from tumor-bearing hosts (TS) whereas, under the same conditions, cultured normal spleen cells (NS) gave little cytotoxicity. The AK effectors were primarily Thy1+, AGM1- and Lyt2- and thus were neither classic cytotoxic T lymphocytes (CTL) nor classic NK cells. These AK cells selectively killed tumor targets of different etiologic origins and did not kill concanavalin-A-induced lymphoblasts. The broad target-cell reactivity of these AK cells was also confirmed by cold target-inhibition experiments. Generation of AK cell correlated with interleukin-2 (IL-2) production, and the levels of AK cells generation paralleled those of IL-2 production. Furthermore, the generation of AK cells was blocked by the anti-IL-2 receptor monoclonal antibody (MAb) (alpha IL-2R), indicating that IL-2 was involved, and thus these AK cells were lymphokine-activated killer (LAK) cells. We previously showed that the expression of AGM1 on LAK precursors disappeared when they differentiated into LAK effectors, indicating that the activated LAK cells lacked AGM1. When examining the serologic phenotype of the LAK precursors in tumor-bearing hosts, we found that they lacked AGM1, which suggested that these LAK precursors were in an "activated" state. These cells were still Thy1-, and were thus different from fully activated LAK effectors which were Thy1+ cells, indicating that the full differentiation of LAK cells in vivo was arrested in the tumor-bearing hosts. We also found that the presence of small amounts of X-irradiated tumor cells prevented the generation of AK cells. These findings suggest that, in the tumor-bearing hosts, the presence of tumor cells triggers the activation of AK precursors; however, the same tumor cells may also be immunosuppressive, which prevents the full differentiation of AK precursors into AK effectors.

Intraluminal interleukin 2 and bacillus Calmette-Guerin for treatment of bladder cancer: a preliminary report

The authors treated 13 patients who had undergone resection of transitional cell carcinoma of the bladder with a combination of 3,500 units of interleukin 2 and half the recommended dose of bacillus Calmette-Guerin. Of the patients 11 (85 per cent) remained free of tumor for a mean of 13 months (range 6 to 24 months). These results are comparable to those with bacillus Calmette-Guerin therapy alone. However, a longer followup with a large number of patients is needed to assess the efficacy of this modality compared to conventional bacillus Calmette-Guerin therapy. Side effects after treatment were minor, self limiting (fever, hematuria and bladder irritability) and lasted for 24 hours.

Immunomodulating activities associated with the cytosol fraction of a 3-methylcholanthrene-induced rat fibrosarcoma--II. Association with polyamine complexes

This paper characterizes the molecular nature of the factors present in cytosol from F-344 rat McFiFi2(s) fibrosarcoma cells (FiCF) which mediate inhibition of PHA-induced lymphoproliferative responses. These are polyamines (spermine/spermidine) conjugated to different protein carriers. Interaction of these complexes with polyamine oxidase (PAO) present in fetal calf or rat serum is responsible of the suppression observed.

Induction of suppressor cells by a tumor-derived suppressor factor

Murine fibrosarcomas produce a factor that activates suppressor cells to inhibit expression of delayed-type hypersensitivity (DTH) responses to dinitrochlorobenzene (DNCB). This tumor-derived suppressor factor (TDSF) was partially purified by preparative isoelectric focusing of spent medium and 3 M KCl extracts of cultured methylcholanthrene-induced and spontaneous fibrosarcomas of C3H/He mice. Incubation of 1 micrograms/ml of a fraction, isoelectric pH less than 2.9, with normal syngeneic spleen cells for 1-6 hr at 37 degrees C induced suppressor cells that inhibited the primary DTH response to DNCB upon intraperitoneal transfer to normal C3H/HeJ mice. TDSF was not present in extracts of either syngeneic embryonic fibroblasts or normal spleen cells or in medium conditioned by normal peritoneal exudate cells but was present in 3 M KCl extracts of and the spent medium from four different cultured murine fibrosarcomas. TDSF activity was not restricted at the major histocompatibility complex. The suppressor cells inhibited the efferent limb of the DTH response because (1) hyporesponsive recipients of TDSF-treated spleen cells had splenic effector T cells capable of transferring DTH to DNCB into naive secondary recipients and (2) the ability of Lyt 1+,2- effector Tdth cells to transfer a secondary DTH response to DNCB was inhibited by co-incubation with macrophages or Lyt 1-,2+ T cells treated with TDSF. Preliminary biochemical analysis suggested that TDSF was an RNA- protein complex. Thus, several murine fibrosarcomas produced a soluble factor that activated splenic suppressor cells to depress the immune response to nonneoplastic antigens. These suppressor factors represent a novel group of regulatory molecules which may be ribonucleoprotein complexes.

Tumour regression after intralesional injection of interleukin 2 (IL-2) in bladder cancer. Preliminary report

Six bladder cancer patients received intralesional injections by needle, under cystoscopic control, of 1969-4046 units (U) of xenogeneic IL-2 of high biological activity (324 U/ml; 397 micrograms/ml protein; 1.22 protein/U ratio). The treatment was spread over 7-54 days and 0.5 ml was injected each time. In 3/6 patients complete tumour regression was seen 43, 60 and 105 respectively days after the first IL-2 injection. In 2 a 70% regression was observed at days 45 and 75. In the last patient massive necrosis throughout the tumour mass was recorded on day 25 at radical cystectomy. In order to evaluate the minimum IL-2 U required to obtain positive clinical results and/or to assess whether the anti-tumour effect observed could be ascribed to the foreign protein of bovine origin contained in our IL-2 preparation, 4 additional bladder cancer patients were treated in 7-14 days with 156-1404 U of a second IL-2 lot with a much lower biological activity and similar protein content (52 U/ml; 289 micrograms/ml of protein; 5.55 protein/U ratio). No clinical or histological improvement was noted over a 42- to 54-day observation period. When we evaluated the 2 groups of patients by Student's t-test for both total U injected and U/kg of body weight (bw) we found a statistically significant differences (0.0025 less than p less than 0.0005 and p less than 0.0005, respectively). In contrast, no difference was seen for the injected protein amounts. The reported observations are in favour of a dose-dependent anti-tumour action mediated by IL-2 instead of foreign proteins. In none of the patients treated were any early or late adverse clinical side effects observed. Immunological monitoring (E, EAC, E-active rosettes, mitogen lymphocyte stimulations and leukocyte migration inhibition in the presence of allogeneic bladder cancer cells) performed on the peripheral blood (PB) showed significant but contrasting modifications after IL-2 injection. There was no clear correlation with the clinical course. The patients in whom we observed complete regression are still tumour free after 2, 4 and 7 months. In addition, in all the patients of the first group we observed an increase in tumour lymphoid infiltrate after IL-2 injection and in 2 patients lymphoid pseudo-follicles were also noted. In 2 of these patients we also observed scar-like areas in the place of the tumours previously seen.

Studies of the mechanisms for the induction of in vivo tumor immunity. VII. Development of specific antitumor immunity in progressors and regressors

The present study was aimed at comparing the development of specific antitumor immunity between hosts with progressively growing tumors and hosts with regressing tumors. The experiments were performed with a Friend virus-induced leukemia FBL-3 in syngeneic C57BL/6 mice. The specific antitumor immunity was determined by in vitro cell-mediated cytotoxicity assay and in vivo tumor neutralization test. Both the systemic immunity (demonstrated in spleen) and immunity developed at tumor site were examined. For progressors, the tumor site was in the peritoneal cavity. For regressors, it was in a subcutaneous site of both flanks. Testing by the cell-mediated cytotoxicity assay showed that immune hosts and regressors had higher levels of systemic immunity than the progressors. However, when lymphocytes isolated from tumor sites were assayed, it was found that there was no remarkable difference between lymphocytes from progressor tumors (PTL) and lymphocytes from regressor tumors (RTL). Both lymphocyte populations were similar in profile analysis; they were characterized as T cells and possessed the same antigenic specificity. Nevertheless, when in vivo tumor transplantation experiments were performed, RTL were found to give protection against FBL-3 challenge whereas PTL consistently failed to do so. On cytomorphological examination, the PTL were seen to contain large amounts of macrophages. The presence of macrophages in PTL appeared to have an inverse relationship to the in vivo protective effect. After removal of macrophages from PTL by Petri dish adherence, the nonadherent PTL were found to give in vivo protection. Furthermore, thymocytes from progressors and macrophages isolated from the progressor tumors were found to suppress the in vivo T-cell-mediated immunity. These findings demonstrated that suppressor T cells and suppressor macrophages were present in tumor-bearing hosts. These suppressor cells could interfere with the function of immune T cells at the efferent arm of the immune response.

The effects of tumor facilitating factor of B16 melanoma on the macrophage

B16 cells produce a tumor facilitating factor (TFF) that increases B16 tumor incidence in mice injected with a small number of B16 cells. TFF was derived from serum-free culture supernatant concentrated on an Amicon PM10 membrane. One milliliter of concentrated material represented the product 10(8) B16 cells during a 6-h incubation. We report data that indicate TFF may act by altering macrophage function. In the nude mouse deficient in T cell, but not macrophage function, the injection of 0.8 ml of TFF facilitated tumor development. Subcutaneous injection of 0.7 ml of TFF induced mouse peritoneal macrophages to spread when removed and plated on glass coverslips. This effect peaked 3 days after injection of TFF and was abrogated by heating the TFF to 70 degrees C for 1 h. The injection of TFF was also able to induce macrophage spreading in nude mice. Injection of viable B16 cells induced spreading, as would be predicted if TFF is produced by B16 cells in vivo. In vitro incubation of peritoneal cells with TFF was also able to induce macrophage spreading. Finally, subcutaneous injection of TFF reduced by 80% the accumulation of peritoneal cells in response to intraperitoneal injection of phytohemagglutinin. We suggest that one mode by which TFF facilitates tumor growth is by reducing the numbers of macrophages chemotaxing to the tumor site.

Effect of interleukin 2 on cytotoxic effectors: I. Short-term culture of the cytotoxic effectors and the in vivo anti-tumor activity of the cultured effectors isolated from tumor site

The effects of interleukin 2 (IL2) on the in vitro and in vivo activity of cytotoxic T cells have been studied. IL2 was produced by W/Fu rat spleen cells cultured with concanavalin A. The IL2 thus prepared gave an optimal T-cell growth-promoting effect at a concentration of 5-20% equivalents of the original preparation. In the primary syngeneic mixed lymphocyte/tumor cell cultures (MLTC) against FBL-3 tumor cells, the addition of IL2 failed to generate a cytotoxic response. However, the cytotoxic response could be generated in MLTC by addition of exogenous macrophages. On the other hand, IL2 could maintain the growth of performed cytotoxic T cells for 3 to 5 weeks. These cytotoxic T cells were generated either by in vitro sensitization (MLC or MLTC) or by in vivo sensitization of B6 mice against a syngeneic tumor FBL-3. In short-term cultures, augmentation of the cytotoxic activity was seen after 10 days' culturing with IL2. The antigenic specificity of the cytotoxic reaction was altered after 28-35 days in culture, and the effectors broadly reactive. When growing a nonadherent population of lymphocytes isolated from FBL-3 ascites tumor, supplementation with IL2 selectively promoted the growth of a T-cell population, resulting in the elimination of the contaminating tumor cells. These purified T cells were highly cytotoxic for FBL-3 cells in vitro and also possessed strong in vivo anti-tumor activity against FBL-3 cells in the adoptive transfer experiments. The present study demonstrates that short-term culture (2-3 weeks) in IL2 promotes the growth of T cells and augments their cytotoxic activity with the appropriate antigenic specificity. IL2 also promoted the selective growth of T cells isolated from tumor site and these T cells showed augmented in vitro and in vivo anti-tumor activity.

Escape of tumours from immunological destruction

This paper reviews the mechanisms of tumour escape from immune destruction that have been delineated in the past 2 decades. Current evidence indicates that the principal escape mechanisms are (i) weak or absent immunogenicity (ii) immunosuppression by tumour antigens or antigen-antibody complexes (iii) induction of suppressor cells and (iv) production of immunosuppressive factors. A classification of tumour escape mechanisms is presented.

Switching on the macrophage-mediated suppressor mechanism by tumor cells to evade host immune surveillance

The present study demonstrates a unique mechanism for tumor cell-induced immunosuppression. In the presence of a nonsuppressive dose of tumor cells, generation of cytotoxic T cells in the mixed lymphocyte culture (MLC) is completely suppressed by adding exogenous (peritoneal) macrophages (PM phi) after the initiation of the MLC. This indicates that tumor cells can switch on a suppressor mechanism through host macrophages. It has further been determined that suppression can be induced only if resident (splenic) macrophages (SM phi) are exposed to tumor cells prior to addition of PM phi. If SM phi and PM phi are simultaneously present with the tumor cells, induction of suppression is completely precluded. These findings indicate that switching on of the suppressor mechanism by tumor cells has a critical requirement for the collaboration of two populations of macrophages, SM phi and PM phi, and their presence in a specific sequence (SM phi preceding PM phi). This may represent one of the mechanisms by which tumor cells evade host immune surveillance.

Evaluation of the immunocompetence of macrophages and the generation of T-cell-mediated cytotoxic response against allogeneic tumor cells in tumor bearers

The present study has examined the competence of peritoneal cells (PC) I of tumor bearers to reverse the immunosuppressive effect of tumor cells, and the ability of the tumor bearers to generate a T-cell-mediated cytotoxic response against allogeneic spleen cells or allogeneic tumor cells. It was found that PC from tumor bearers possess a greater ability to reverse the tumor cell immunosuppression in normal mice. In contrast to normal hosts, the cytotoxic responses of the tumor bearers against allogeneic tumor cells cannot be restored by PC from normal mice or from tumor bearers. The ineffective cytotoxic response in tumor bearers was not due to deficient T responders or T helpers. Rather, it was due to the presence of suppressor cells which were adherent, radioresistant and resistant to anti-Thy-1.2 antibody lysis, and thus were likely to be macrophages. The suppressor macrophages were present only in the spleen and were absent from the peritoneal cavity of the tumor bearers. Their suppressive effect can only be exerted in the presence of tumor cells. These results demonstrate the dichotomy of macrophage function, peritoneal macrophages from the tumor bearers showing increased activity of augmentation of T-cell-response whereas the splenic macrophages cause suppression of the T-cell-response.