Mechanisms by which human gliomas may escape cellular immune attack

HLA-Dr Expression by Tumor Cells Compared with Survival in High Grade Astrocytomas

Frozen samples from 78 high grade astrocytomas were reacted with a monoclonal antibody directed against HLA-Dr invariant chain. Survival data was obtained for all 78 cases. HLA-Dr was expressed by a proportion of tumor cells in 65/78 (83 %). Comparison of the survival of positive and negative cases showed that the difference was not statistically significant (p = 0.4). The relevance of the finding is discussed in the context of the immunoreaction to brain tumors.

Cellular cancer vaccines: an update on the development of vaccines generated from cell surface antigens

A recent advance in anti-cancer therapies has been the use of cancer cells to develop vaccines. However, immunization with cancer cell-based vaccines has not resulted in significant long-term therapeutic benefits. A possible reason for this is that while cancer cells provide surface antigens that are targets for a desired immune response, they also contain a high abundance of housekeeping proteins, carbohydrates, nucleic acids, lipids, and other intracellular contents that are ubiquitous in all mammalian cells. These ubiquitous molecules are not the intended targets of this therapy approach, and thus, the immune response generated is not sufficient to eliminate the cancer cells present. In this review, a discussion of the cell surface of cancer cells is presented in relation to the goals of improving antigen composition of cancer cell-based vaccines. Strategies to enrich vaccines for cancer-specific antigens are also discussed.

Cellular and functional characterization of immunoresistant human glioma cell clones selected with alloreactive cytotoxic T lymphocytes reveals their up-regulated synthesis of biologically active TGF-beta

Two immunoresistant (IR) glioma cell variants, 13-06-IR29 and 13-06-IR30, were cloned from 13-06-MG glioma cell populations after receiving continuous immunoselective pressure from multiple alloreactive cytotoxic T lymphocyte (aCTL) preparations. Reapplication of aCTL immunoselective pressure to the IR clones, displaying a partial regain in sensitivity to aCTL after removal of the selective pressure, restored the resistance. The IR variants exhibited cross-resistance to non-human leukocyte antigen (HLA)-restricted effector cells and gamma-irradiation, but not to carmustine. The IR clones were characterized for factors that might contribute to the immunoresistance. The aCTL adhesion to extracellular matrix extracts derived from either the IR clones or the parental cells was similar and not impaired. Furthermore, aCTL binding to parental cells and IR clones was equal. Down-regulation of the cell recognition molecules, class I HLA or intercellular adhesion molecule-1 (ICAM-1), that would inhibit their recognition by aCTL was not observed on the IR clones. The down-regulation of Fas by the IR clones correlated with their resistance to FasL-induced apoptosis. HLA-G or FasL that might provide an immunotolerant environment or provide a means of counterattack to aCTL, respectively, were not associated with the IR phenotype. The aCTL, coincubated with the IR clones and parental cells, displayed up-regulation of multiple secreted cytokines. A significant up-regulation of bioactive transforming growth factor (TGF)-beta was observed in the IR clones compared with the parental cells. These data suggest that increased secretion of bioactive TGF-beta may inhibit aCTL lysis of the IR clones. Disruption of the TGF-beta signaling pathway may circumvent the resistance.

The cancer stem cell: evidence for its origin as an injured autoreactive T cell

This review explores similarities between lymphocytes and cancer cells, and proposes a new model for the genesis of human cancer. We suggest that the development of cancer requires infection(s) during which antigenic determinants from pathogens mimicking self-antigens are co-presented to the immune system, leading to breaking T cell tolerance. Some level of autoimmunity is normal and necessary for effective pathogen eradication. However, autoreactive T cells must be eliminated by apoptosis when the immune response is terminated. Apoptosis can be deficient in the event of a weakened immune system, the causes of which are multifactorial. Some autoreactive T cells suffer genomic damage in this process, but manage to survive. The resulting cancer stem cell still retains some functions of an inflammatory T cell, so it seeks out sites of inflammation inside the body. Due to its defective constitutive production of inflammatory cytokines and other growth factors, a stroma is built at the site of inflammation similar to the temporary stroma built during wound healing. The cancer cells grow inside this stroma, forming a tumor that provides their vascular supply and protects them from cellular immune response.

As cancer stem cells have plasticity comparable to normal stem cells, interactions with surrounding normal tissues cause them to give rise to all the various types of cancers, resembling differentiated tissue types. Metastases form at an advanced stage of the disease, with the proliferation of sites of inflammation inside the body following a similar mechanism. Immunosuppressive cancer therapies inadvertently re-invigorate pathogenic microorganisms and parasitic infections common to cancer, leading to a vicious circle of infection, autoimmunity and malignancy that ultimately dooms cancer patients. Based on this new understanding, we recommend a systemic approach to the development of cancer therapies that supports rather than antagonizes the immune system.

Preliminary results of active specific immunization with modified tumor cell vaccine in glioblastoma multiforme

OBJECT

Treatment for glioblastoma multiforme has failed to show any progress for decades. While specific immunization with tumor cells modified with Newcastle-Disease-Virus (NDV) has been reported successful in some extracerebral tumors, its effect on glioblastoma is unknown. We report on 11 patients, in whom this approach was analyzed.

METHODS

A vaccine was produced from autologous tumor cell cultures of 11 patients with glioblastoma. After completed surgery and radiotherapy an intracutaneous vaccination was performed 4 times with a 2 week interval and finally after 3 months. Local reactions, general side effects and survival were monitored closely.

RESULTS

The local reaction of the skin after injection of vaccine increased from 1.67 to 4.05 cm2 in 8 weeks. The skin reaction after parallel injection of inactivated, untreated tumor cells increased from 0.11 to 1.09 cm2. The median survival was 46 weeks (mean 60 weeks). No side effects were noted.

CONCLUSION

Active specific immunization with NDV-modified glioblastoma cells produced a noticeable peripheral immune response. In this preliminary series survival of patients was not significantly longer after active specific immunization than after combined treatment of surgery, radiotherapy and chemotherapy. As there were no side effects, however, active specific immunization may be considered an alternative in the management of glioblastoma.

Long-term remission of malignant brain tumors after intracranial infection: a report of four cases

OBJECTIVE

This report describes four patients with malignant brain tumors in whom regression or cure seems to be related to infection with bacteria.

METHODS

An analysis of the four clinical cases reported and a review of the literature produced a comprehensive body of both experimental and clinical data concerning the antineoplastic properties of bacteria.

RESULTS

Although direct oncolytic effects from bacteria have been suggested, immune adjuvant responses to tumor suppression are emphasized. In one of our patients, infiltration of numerous granulocytes and lymphocytes into the tumor at the time of initial surgery was observed, suggesting that a spontaneous immune reaction had begun. Also, in two other patients, tumor aggression occurred in association with a bacterial process that was not in direct contact with the tumor. In three of the cases described, Enterobacter aerogenes was recovered from the microbial cultures. Whether the presence of this organism was coincidental or whether this organism plays an important role in tumor defense is not known; however, a specific cross-reactive immunological attack to the tumor is suggested.

CONCLUSION

The case histories presented in conjunction with the relevant literature reviewed support the concept that microbial infections may influence immune responses in brain tumor defense.

Immune infiltrates and cytokines in gliomas

Frozen sections of 21 gliomas were analysed to characterize inflammatory infiltrating cells, HLA-DR antigen expression and cytokine secretion. Mononuclear cells infiltrating the tumours were mostly macrophages, which were detected in 100% of cases, and expressed HLA-DR antigens. Lymphocytes were less frequently seen and expressed the CD8 phenotype. Interleukin-1 beta (IL-1 beta) and Interleukin-6 (IL-6), two cytokines mainly produced by activated cells of the macrophage lineage, were demonstrated especially in neoplastic astrocytes. IL-1 beta immunoreactivity was detected in all tumours, and was prevalent in more anaplastic gliomas; IL-6 was found in anaplastic gliomas and in glioblastomas. IL-1 receptors were expressed by both infiltrating macrophages and neoplastic astrocytes in the gliomas analysed. These findings suggest that cytokine production in gliomas seems not related to immune reactions against the tumour and their synthesis by anaplastic astrocytes could follow an unregulated activation of many metabolic processes after neoplastic transformation.

Therapy of glioblastoma multiforme: a cumulative experience of 10 years

PURPOSE

Comparison of the effect of different therapeutic modalities on survival time of patients with glioblastoma multiforme operated on during the last decade (1980-1990).

PATIENTS AND METHODS

The records of 157 consecutive patients with the histological diagnosis of glioblastoma multiforme were analysed for survival with respect to age of patients, extent of surgery, influence of re-operation and adjuvant postoperative treatment. The latter included fractionated radiotherapy, chemotherapy (BCNU. CCNU with Vincristine) and photodynamic therapy (PDT).

RESULTS

Analysis of variance showed a significant effect for survival after macroscopically radical surgery (p = 0.005), postoperative radiotherapy (p < 0.001), chemotherapy (p < 0.01). Low age (p < 0.05) and a postoperative Karnofsky performance score (KPS) > or = 60 (p < 0.001) had a positive influence: the site of tumour and pre-operative presence of seizures had no significant influence (p > 0.1) on survival time.

CONCLUSION

We conclude that the current adequate management of glioblastoma multiforme should include surgical resection followed by adjuvant treatment such as radiotherapy and chemotherapy.

The future of therapy for glioblastoma

Effective therapy for malignant gliomas has centered on traditional approaches such as surgery and radiation therapy. Over the past two decades, more innovative approaches involving the use of chemotherapy and immunotherapy have been developed. Although these techniques have improved the quality of survival for many patients, the median survival following diagnosis and adjuvant treatment still remains only about a year. Recently, genetically engineered viruses for gene transduction and targeted cell killing have been used successfully in the experimental treatment of glioblastoma multiforme. We provide a review of the current and possible future therapies for malignant glioma with the belief that molecular biologic and genetic techniques offer the greatest hope of significantly altering the course of disease.

Immunocytochemical study of macrophages and microglial cells and extracellular matrix components in human CNS disease. 1. Gliomas

We have used an immunocytochemical approach to investigate the inter-relationships between astrocytes, macrophages and microglia and the extracellular matrix components fibronectin and laminin, in 27 gliomas. Using recently available markers to macrophages and microglia (monoclonals Mac387, KP1 and the lectin RCA-1) and antisera to GFAP, fibronectin and laminin, we have described the reactions of these cells and the extracellular matrix. We found RCA-1 to be the superior marker for detecting most macrophages and microglia. There were more macrophages and microglia in high-grade gliomas than in low-grade. RCA-1 also reacted with endothelial cells in normal and reactive brain but showed markedly less affinity for endothelium in an close to gliomas. A possible role for the extracellular matrix in the astrocyte, macrophage and microglial reactions is discussed in the broader context of their role in the immune response.

Immunobiology of brain tumors

In summary, many actual interactions between tumors in the CNS and the immune system have been demonstrated. The normal brain does not possess a lymphatic system and is partially hidden from the systemic immune system by the BBB, furthermore brain cells do not express MHC antigens which are necessary for the initiation of an immune response. In pathological conditions however, immunocompetent cells may find their way through transformed endothelial cells. Microglia and astrocytes may function as antigen presenting cells. Glioma cells when stimulated by cytokines such as IFN gamma can be induced to express MHC class I and class II antigens, thus making them more susceptible to an immune attack. In addition glioma cells are capable of secreting several cytokines including IL 1, IL 3 and IL 6 also involved in the generation of an immune response. Indeed, a functional analysis of lymphocytes infiltrating gliomas has revealed the accumulation at the tumor site of cytotoxic T lymphocytes as well as NK cells. However host-immune responses against gliomas seem to be weak in comparison to other cancers. Glioma cells are known to secrete TGF beta 2 and PGE 2 which may in part be responsible for this lack of immune response, thus shielding themselves from immune attack. In order to be recognized by the immune system the tumor cells must express TAA in addition to MHC antigens, and such TAA have been identified by MAbs. These MAbs can be used for "targeted" therapy when coupled to toxic agents or radionuclides. Preclinical studies have shown that, after intravenous or intracarotid injection, there is specific accumulation of the MAb in the tumor but in insufficient amounts for therapeutic use. The relatively small amount of MAb binding to the tumor in vivo can be due to several factors: not all the cells in a single tumor express a given tumor-associated antigens, the MAb may have a low affinity for the antigen, the BBB may hinder the passage of the MAb. Attempts have been made to overcome these drawbacks by opening the BBB for example. In addition MAbs can readily be used for the treatment of carcinomatous meningitis. There has been little success in the development of immunotherapy with IFN beta 1 and even less with adoptive immunotherapy using LAK cells plus IL 2. TIL as well as LAK cells can be expanded in vitro with IL2 and it is feasible to reinject these cells into the tumor site.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunology of central nervous system tumors

With progress in cellular immunology and the development of hybridoma technology, the idea of manipulating host-tumor immune interactions to improve the prognosis of brain tumors has aroused renewed interest. Although no brain tumor-specific antigens have been found, and in spite of the wide antigenic heterogeneity of brain tumor cells, some monoclonal antibodies possessing restricted specificity have been isolated and their potential clinical applications investigated. One of the most pronounced changes in the cellular immune responses of brain tumor patients is a profound depression of the T4-helper lymphocytes. Clinical and laboratory trials are under way to assess the ability of lymphokines, such as gamma-interferon or interleukin-2, to restore immunologic competence in these patients and potentiate a specific anti-tumor immunologic response. Recent work suggests that the endothelium-astrocyte complex may have a pivotal role in assisting the escape of brain tumors from the host's immunologic responses, since it is responsible for the intracerebral sequestration of antigens and local anti-tumor responses. In this review, the data on the antigenic properties of central nervous system tumors and the host's humoral and cellular immune responses to them are analyzed and potential immunologic therapies are discussed.

Growth factors in the tumorigenicity of a brain tumor cell line

We studied a virally induced canine gliosarcoma brain tumor cell line capable of producing brain tumors in vivo following intracerebral inoculation of the cells into the brains of adult mongrel dogs. Cloned populations from this cell line differed in their ability to produce brain tumors in vivo. In vitro transforming growth factor-beta secretion by each clone correlated with in vivo tumorigenicity. Mitogenic activity like that produced with platelet-derived growth factor was also secreted by each clone and correlated with in vivo tumorigenicity. Epidermal growth factor and transforming growth factor-alpha production was not detected in any of the clones of canine gliosarcoma cells. Although only some of the brain tumor cell clones were able to produce tumors in immunologically normal dogs, brain tumors were produced in all dogs pretreated with cyclosporin and in all "nude" mice, suggesting that tumor immunology plays an important role in this brain tumor model. In vitro cloning efficiency of each brain tumor cell clone also correlated with in vivo tumorigenicity. We postulate that transforming growth factor-beta may both stimulate brain tumor cell growth and inhibit host antitumor immune surveillance.

Treatment of glioma with intratumoral instillation of autologous lymphocytes

Autologous lymphocytes were instilled into the tumor in a girl 15 years of age who had presented with a recurrent left frontoparietal astrocytoma 1.5 years after surgery, radiation, and chemotherapy. She had remissions for 5 weeks, 5 months, and 20 months after the first, second, and third instillations, respectively. The usefulness of intratumoral instillation of autologous lymphocytes [or preferably lymphokine activated killer (LAK) cells with interleukin-2 is demonstrated in such recurrent astrocytomas.

Mononuclear cell infiltration in central portions of human astrocytomas

The mononuclear cell infiltration in the central portion of human low- and high-grade astrocytomas has been examined using monoclonal antibodies to cell surface differentiation antigens. There was no significant difference between the number of T cells, B cells, or macrophages. The OKT8+ (suppressor/cytotoxic) T cell population was the major lymphocyte subset in the infiltrates. There was, however, indirect evidence for a proportion of the total OKT8+ cells being natural killer cells. Overall, there was a significant difference in the number of macrophages compared to the total lymphoid cell population. Several cell types seem to play an equal role in the cellular and humoral immune response within the center of the tumors, as distinct from that occurring at the periphery.

Lack of suppressive activity of human primary melanoma cells on the activation of autologous lymphocytes

Previous studies have indicated that primary but not metastatic melanomas were able to stimulate the proliferation of autologous (Auto) peripheral blood lymphocytes (PBL) in 73% of cases. On the other hand, 57% of the metastatic melanomas were shown to be suppressive when melanoma cells (Me) were admixed with Auto-PBL stimulated with allogeneic (Allo) PBL or interleukin 2 (IL-2) at the beginning of a 6-day incubation period. Here, we report that the suppressive activity of Me is a functional characteristic associated with a particular stage of the disease. In fact, we found that none of the 11 primary tumors tested were able to inhibit the proliferative response of Auto-PBL to Allo-PBL or IL-2 at all the doses of tumor cells used. The generation of lymphocytes cytotoxic against Auto-Me or K562 was also not inhibited. Of the 11 primary tumors checked for suppression, 8 were able to stimulate Auto-PBL in a primary mixed lymphocyte tumor culture. We conclude that opposite functions, stimulation and inhibition of autologous lymphocyte responses are characteristics of primary and metastatic Me, respectively.

Role of the blood-brain barrier in the establishment of the immune response against polyoma virus-induced cerebral tumours in hamsters

The existence of an immunological blood-brain barrier (BBB) is well established but its role in cerebral tumour immunology is less well defined. Attempting to clarify this problem we tested the graft rejection of polyoma virus-induced central nervous (CNS) tumours in hamsters after systemic or intracerebral immunization with polyoma virus. Animals were immunized by intracerebral or subcutaneous inoculations of polyoma virus before tumours were induced by intracerebral or intramuscular graft of polyoma-transformed hamster neuroglial cells. The growth of cerebral and muscular tumours was significantly inhibited in animals immunized subcutaneously. In animals immunized intracerebrally the inhibition of growth was highly significant for cerebral tumours and only very slight for intramuscular tumours. These results suggest that the blood-brain barrier allowed immunocompetent effector cells to penetrate inside the CNS but prevented the locally elicited cell-mediated immune response from diffusing outside the CNS. The ability of the brain to develop a local immune response and the partial lack of circulation of immunocompetent cells to cross the BBB could be mainly responsible for the special immune status of the CNS and may greatly interfere with the establishment of an efficient immune response toward brain tumours.

Ultrastructural features of the lymphocyte-stimulated halos produced by human glioma-derived cells in vitro

Many glioma-derived cell lines have the capability of escaping cell-mediated immune attack. One mechanism of escape is the secretion of a hyaluronidase-sensitive mucopolysaccharide coat by these cells. This coat prevents contact and tumor cell killing by specific cytolytic allogeneic lymphocytes. The production of the coat by the tumor cells is stimulated by a macromolecular factor released by peripheral blood mononuclear (PBMC) cells in culture. We have examined the morphologic and ultrastructural features of this extracellular matrix. Three coat-producing lines were studied. Under phase contrast light microscopy, the coat is a clear pericellular 'halo'. To stain this zone, ruthenium red and Alcian Blue 8 G stains, which bind to acid mucopolysaccharides (to a large extent, hyaluronic acid), were used. The two stains produced similar results. With light microscopy, a weblike pattern of stain was evident throughout the halo region. With transmission electron microscopy, staining was found along the plasma membrane of the glioma cells and their microvilli, stretching in long, branching filaments from these surfaces and, in some instances, from one microvillus to the next. Since mucopolysaccharide matrices have a large aqueous component, it was necessary to determine whether dehydration alters the stain pattern. Therefore, undehydrated ruthenium red stained specimens from each culture were embedded in Quetal 651 (Ted Pella, Inc., Tustin, CA), a water soluble plastic. No morphologic differences were noted between the hydrated and dehydrated specimens. This study indicates that numerous long microvilli and a secreted mucopolysaccharide matrix are important structural elements of the lymphocyte-stimulated tumor cell halo in vitro. The mechanism by which the PBMC factor stimulates coat formation and the importance of the coat in in vivo tumor defenses remain to be elucidated.

In vitro killing of human glioblastoma by interleukin-2-activated autologous lymphocytes

Culture of peripheral blood lymphocytes (PBL) from brain-tumor patients with recombinant interleukin-2 (IL-2) results in the activation of lymphokine-activated killer cells (LAK) with the capacity to lyse autologous and allogeneic glioblastoma. In this study, PBL obtained from brain-tumor patients were cultured with or without IL-2 for 3 to 7 days and then tested for their ability to lyse target cells in a 4-hour chromium release cytotoxicity assay. The PBL were drawn 1 to 2 weeks following operative tumor debulking. Cells used as targets included fresh brain-tumor cells obtained at the time of craniotomy, fresh brain-tumor cells grown from 1 to 3 weeks in tissue culture, fresh autologous PBL, and allogeneic glioblastoma cells grown in tissue culture. Peripheral blood lymphocytes from brain-tumor patients that were cultured without IL-2 did not significantly lyse autologous or allogeneic glioblastoma. However, when these PBL were cultured with IL-2, LAK were generated which produced marked lysis of autologous as well as allogeneic tissue-culture glioblastoma in all of eight cases. Significant lysis of autologous fresh tumor by patient LAK was observed in four of five experiments. By contrast, patient LAK did not kill autologous normal PBL. The ability to generate LAK was not influenced by the patient's age, previous therapy, or the administration of steroids.

Autologous cellular immune response to primary and metastatic human melanomas and its regulation by DR antigens expressed on tumor cells

Evidence for heterogeneity of several biological features of human malignant melanoma (Me) like morphology, cytogenetics, oncogenes activation, antigenic expression, metastatizing capacity and procoagulant activity are briefly reviewed in an attempt to distinguish findings related to primary vs. metastatic lesions. In our own studies monoclonal antibodies were used to study expression of MHC class I, class II products and of Me-associated antigens (MAA) on primary and metastatic Me cells. High expression of class I antigens was found in a high percentage of both primary and metastatic tumors, whereas DR and MAA showed a significant variation (from 3 to 90% of cells) in expression both in primary and in metastatic Me. When autologous cell-mediated immune responses were evaluated, it was found that Me cells from primary tumors but not those from lymph node metastases were able to stimulate autologous lymphocytes to proliferate and become cytotoxic for autologous Me. Clonal analysis of cytotoxic lymphocytes was then carried out in order to see whether the lack of lymphocytes reactivity to metastatic cells was due to the absence or to a low frequency of cytotoxic cells in the unstimulated PBL. CTL clones cytotoxic for autologous Me (Auto-Me) cells were indeed isolated. Three classes of CTL clones were identified: 1) one which is cytotoxic for Auto-Me; 2) a second one which lyse Auto-Me and allogeneic Me; and 3) a third one which is cytotoxic for Auto-Me and allogeneic normal and neoplastic cells. Metastatic Me cells, however, had the ability to suppress the stimulation of autologous PBL by alloantigens or IL-2. This effect was dose-dependent and was not due to absorption of IL-2 by Me cells. Since it has been reported that Me cells express class II MHC antigens, we investigated whether there was any correlation between autologous immune responses and DR expression on Me cells. Autologous lymphocytes stimulation was found to occur only with DR+ Me cells from primary lesions, whereas metastatic cells, either DR+ or DR-, did not stimulate autologous PBL. Moreover, the suppressive effect of metastatic Me cells was associated with their expression of DR antigens. The modulation of DR antigens on Me cells by Interferon-gamma correlated positively with their suppressive capacity. Thus, it appears that primary Me can behave differently from the metastatic one in their interactions with the immune system of autologous host. These findings suggest that DR antigens on Me cells may have an important role in the regulation of autologous immune responses.

The inhibition of lymphocyte stimulation by autologous human metastatic melanoma cells correlates with the expression of HLA-DR antigens on the tumor cells

Previous studies indicated that peripheral blood lymphocytes from patients (Pt-PBL) with lymph node metastatic melanomas proliferated in vitro and developed into tumor-restricted cytotoxic lymphocytes in response to alloantigens or interleukin 2 (IL-2). However, Pt-PBL were not stimulated by irradiated autologous metastatic melanoma (Auto-Me) cells. In the present study we report that the lack of stimulatory activity of Auto-Me cells may be due to a suppressive effect exerted by Auto-Me cells on the responder lymphocytes. In fact, we found that in 62% of cases examined, the addition of 5-10% Auto-Me cells to Pt-PBL cultures strongly inhibited both proliferation and the generation of tumor cytotoxic lymphocytes induced by alloantigens or IL-2. The inhibition was dose-dependent and tumor-restricted, and was not due either to toxicity, medium depletion or IL-2 absorption by Auto-Me cells. Normal fibroblasts, K562 cells and autologous E-lymphocytes were not suppressive. Auto-Me cells were able to inhibit Pt-PBL responses only when added during the first 24 h of culture and not later. Phenotypic analysis of Auto-Me cells using monoclonal antibodies directed against HLA-A,B,C, HLA-DR and melanoma-associated antigens revealed that the expression of high levels of DR antigens on Auto-Me cells was associated with an elevated suppressive activity. Conversely, Auto-Me cells with low or undetectable levels of DR antigens were not inhibitory. Furthermore, the increased expression of DR antigens on Auto-Me cells obtained by in vitro treatment with human interferon gamma (IFN-gamma) also resulted in an increased suppressive activity. We conclude that HLA-DR+ metastatic melanoma cells can interfere with the generation of an anti-tumor immune response, thus potentially favoring the escape of the tumor from the host's control mechanism.

Particular features of cell-mediated immunity in patients with anaplastic gliomas. A comparison with kidney and bladder cancer patients

The authors studied 24 patients affected by anaplastic gliomas in regard to the killer (Antibody-Dependent Cellular Cytotoxicity) and natural killer (Spontaneous Lymphocyte-Mediated Cytotoxicity) immunological functions, by counting the Cr51 release in Change liver and K 562 cell cultures, respectively. These parameters were also evaluated in 24 healthy donors as control, in 24 patients affected by bladder cancer and in nine cases of kidney cancer. Our data show, pre-operatively, a statistically significant impairment of ADCC and SLMC activity in glioma patients as compared both with controls, bladder and kidney cancer patients. The particular impairment of K and NK functions in gliomas is discussed with regard to the specific features of Central Nervous System malignancies. An improvement of ADCC activity was also found in the post-operative samples. This finding confirms other reports about partial restoring of altered immunocompetence after surgery, suggesting a link between extention of tumor mass and impaired immunological reactions.