Cell-mediated immunity to tumor cells

Immunogenicity of Lewis Lung Carcinoma in C57BL/6 Mice. I. Tumor-Associated Antigen(S) in Peripheral Blood, Thymus and Spleen of Tumor-Bearing Mice

Some aspects of the immunogenicity of the Lewis lung (3LL) carcinoma in C57BL/6 mice are reported. Immediately after i.m. tumor transplant, and for approximately 24 h, tumor antigens were found in the blood stream. They were observed again on the 5th–6th day, when circulating tumor cells could also be noticed. Soluble immune complexes were detected in the blood sera of tumor-bearing mice from the 11th day, indicating that the host had reacted to the neoplastic antigen stimulation with immunoglobulin synthesis. Furthermore, tumor antigens were observed on some circulating lymphocytes, as well as in the thymus and in the spleen. In spleen sections, atypical mitoses also showed the presence of tumor cells. We obtained the in vitro binding of 3LL-antigens, present in 3 M KCl-solubilized extracts, to normal T lymphocytes prepared from healthy C57BL/6 mice. The possibility that circulating T lymphocytes aspecifically bind tumor antigens, carrying them to the thymus, is discussed.

Therapeutic vaccination with tumor cells that engage CD137

Therapeutic cancer vaccination is based on the finding that tumors in both humans and experimental animals, such as mice, express potential immunological targets, some of which have high selectivity for cancer cells. In contrast to the successful vaccination against some infectious diseases, where most vaccines induce neutralizing antibodies that act prophylactically, the aim of therapeutic cancer vaccines is to treat established tumors (primarily micrometastases). Since most tumor-destructive immune responses are cell-mediated, therapeutic cancer vaccination needs to induce and expand such responses and also to overcome "escape" mechanisms that allow tumors to evade immunological destruction. Tumor antigens (as with other antigens) are presented by "professional" antigen-presenting cells, most notably dendritic cells (DC). Therefore DC that have been transfected or "pulsed" to present antigen provide a logical source of tumor vaccines, and some encouraging results have been obtained clinically as well as in preclinical models. An alternative and more physiological approach is to develop vaccines that deliver tumor antigen for in vivo uptake and presentation by the DC. Vaccines of the latter type include tumor cells that have been modified to produce certain lymphokines or express costimulatory molecules, as well as cDNAs, recombinant viruses, proteins, peptides and glycolipids which are often given together with an adjuvant. Several studies over the past 5 years have demonstrated dramatic therapeutic responses against established mouse tumors as a result of repeated injections of agonistic monoclonal antibodies (MAbs) to the costimulatory molecule CD137 (4-1BB). However, the clinical use of such MAbs may be problematic since they depress antibody formation, for example, to infectious agents. The alternative approach to transfect tumor cells to express the CD137 ligand (CD137L) increases their immunogenicity, but vaccination with tumor cells expressing CD137L is ineffective in several systems where injection of anti-CD137 MAb produces tumor regression. Recent findings indicate that a more effective way to engage CD137 towards tumor destruction is to transfect tumor cells to express a cell-bound form of anti-CD137 single-chain Fv fragments (scFv). Notably, tumors from melanoma K1735, growing either subcutaneously or in the lung, could be eradicated following vaccination with K1735 cells that expressed anti-CD137 scFv. This was in spite of the fact that K1735, as with many human neoplasms, expresses very low levels of MHC class I and has low immunogenicity. Similar results were subsequently obtained with other tumors of low immunogenicity, including sarcoma Ag104. We hypothesize that the concomitant expression of tumor antigen and anti-CD137 scFv effectively engages NK cells, monocytes and dendritic cells, as well as activated CD4(+) and CD8(+) T cells (all of which express CD137) so as to induce and expand a tumor-destructive Th1 response. While vaccines in the form of transfected tumor cells can be effective, at least in mouse models, the logical next step is to construct vaccines that combine genes that encode molecularly defined tumor antigens with a gene that encodes anti-CD137 scFv. Before planning any clinical trials, vaccines that engage CD137 via scFv need to be compared in demanding mouse models for efficacy and side effects with vaccines that are already being tested clinically, including transfected DC and tumor cells producing granulocyte-macrophage colony-stimulating factor.

Immunoprevention of cancer poses a challenge to pharmacological research

The evolving understanding of the molecular mechanisms of carcinogenesis establishes that the long latency period would offer numerous opportunities for intervention before the final step of fully developed malignancy has been reached. Immunoprevention of cancer may be a new approach to cancer control, by eliminating the cellular minimal deviations that are seen in the early phases of carcinogenesis. Available results of immunotherapy of preneoplastic lesions and data on anticarcinogenesis with immunoregulators in experimental models are in good accordance with theoretical expectations. However, clinical research on immunoregulators still focuses on the treatment of advanced cancer. The major problem hampering a wider application of immunoregulators in cancer prevention is the possibility of potential adverse effects, which are largely unknown. The promotion of future research in this area is essential. Moreover, the ethical issues of intervention trials in cancer must be discussed, by considering the potential psychological and social consequences.

Interferons in precancer and cancer prevention: where are we?

Clinical research on interferons (IFN) still focuses on the treatment of advanced cancer. The research strategy eventually must be reevaluated. The cellular minimal deviations that are seen in early phases of carcinogenesis might be the most rational target for immune interventions. That biologic response modifiers have considerable capacity to prevent induction and development of malignant neoplasias has been demonstrated in several animal systems. Even the few clinical studies available at present on the treatment of preneoplastic lesions with IFN have definitely shown more success than those involving treatment of advanced tumors. In addition, there is experimental evidence that IFN might be suitable candidates for immunoprevention. The major problems hampering a wider application of IFN in immunoprevention is that they cause adverse effects. Unfortunately, we do not know much about the specific mechanisms involved in the immune control of human tumor development during the initial and the latency phases of carcinogenesis. More research is needed in this area. In this article the state of the art of using IFN for treating preneoplastic lesions is reviewed, and also we report some of our experimental results on IFN and anticancerogenesis.

Nonlinear dynamics of immunogenic tumors: parameter estimation and global bifurcation analysis

We present a mathematical model of the cytotoxic T lymphocyte response to the growth of an immunogenic tumor. The model exhibits a number of phenomena that are seen in vivo, including immunostimulation of tumor growth, "sneaking through" of the tumor, and formation of a tumor "dormant state". The model is used to describe the kinetics of growth and regression of the B-lymphoma BCL1 in the spleen of mice. By comparing the model with experimental data, numerical estimates of parameters describing processes that cannot be measured in vivo are derived. Local and global bifurcations are calculated for realistic values of the parameters. For a large set of parameters we predict that the course of tumor growth and its clinical manifestation have a recurrent profile with a 3- to 4-month cycle, similar to patterns seen in certain leukemias.

Early appearance and activation of natural killer cells in tumor-infiltrating lymphoid cells during tumor development

We investigated NK cell infiltration into tumor developing lesions at early stage of tumor development after intraperitoneal inoculation of 3LL lung carcinoma into syngeneic C57BL/6 mice. Natural killer (NK) cells, which were detected by anti-NK 1.1 monoclonal antibody (mAb), remarkably increased in number in tumor-developing lesions (peritoneal cavity) as early as day 3 after inoculation of 3LL. The tumor-infiltrating NK cells from 3LL-inoculated mice produced a high level of interferon-gamma by co-culture with 3LL and showed enhanced cytotoxic activities against both NK-sensitive (YAC-1) and NK-resistant (3LL and P815) tumors. Furthermore, mice depleted of NK cells by injection of anti-NK 1.1 mAb or anti-asialo GM1 antibody showed shorter survival times after intraperitoneal inoculation of 3LL when compared with control mice. These results suggest that NK cells infiltrate the tumor-developing lesion at an early stage and may participate in the early protection against tumors through production of a high amount of interferon-gamma and enhanced cytotoxicity at tumor-bearing sites.

Mechanism of target cell recognition by CD3- LGL. I. Development of a monoclonal antibody to a K562-associated target cell antigen

In an attempt to identify the target recognition molecule(s) involved in the interaction between CD3- large granular lymphocyte (LGL) and a tumor cell target, monoclonal antibodies (mAb) to NK-susceptible K562 tumor cell membrane glycoproteins were developed. After screening by ELISA for reactivity to K562 membrane glycoproteins, two monoclonal antibodies were identified (mAb 35 and mAb 36). One of the monoclonal antibodies (mAb 36) was found to inhibit conjugation between LGL and K562 target cells and also to inhibit lysis of K562 by LGL. Upon further testing, mAb 36 also inhibited the binding between LGL and other NK-susceptible target cells, e.g., Daudi and Molt 4. In contrast, mAb 35, even though binding to K562, did not inhibit the binding of LGL to tumor targets and therefore was used as an isotype control. When mAb 36 was utilized as an affinity matrix, bound proteins specifically inhibited CD3- LGL-K562 conjugation. Experiments involving tunicamycin treatment of tumor target cells demonstrated that mAb 36 recognized a carbohydrate moiety rather than the protein core. Therefore, these data suggested that the target cell recognition molecule which is recognized by mAb 36 appears to be a membrane carbohydrate-associated molecule.

Mechanism of target cell recognition by natural killer cells: characterization of a novel triggering molecule restricted to CD3- large granular lymphocytes

In an attempt to identify a molecule in target recognition by CD3- large granular lymphocytes (LGL), we have generated a rabbit antiidiotypic (anti-ID) serum against a monoclonal antibody (mAb 36) that reacted with the cell membrane of K562. Flow cytometry analysis demonstrated that the anti-ID serum bound selectively to CD3- LGL and that F(ab')2 fragments of the anti-ID serum blocked both target cell binding and lysis by NK cells. Stimulation of CD3- LGL with F(ab')2 fragments resulted in the release of serine esterases and the secretion of interferon gamma. Furthermore, anti-ID F(ab')2 antibodies crosslinked to anti-DNP F(ab')2 mediated directed cytotoxicity of a non-natural killer (NK)-susceptible mouse target (YAC-1) via this surface ligand. These functional reactivities were only removed by adsorption with the specific idiotype. Protein analysis showed that the anti-ID serum immunoprecipitated 80-, 110-, and 150-kD proteins. Using this anti-ID, a partial cDNA was cloned and an antipeptide antiserum was made against the portion of the predicted amino acid sequence that corresponded to a portion of the ID binding region. This antipeptide serum exhibited similar functional and biochemical reactivities to those observed with the anti-ID serum. These data suggest that the cell surface moiety recognized by the anti-ID and anti-p104 is novel and is selectively involved in both recognition and triggering of NK-mediated lytic function.

Immuno-chemotherapy of advanced colorectal cancer with alpha-2a interferon and 5-fluorouracil. Immunopharmacological studies

Twelve patients with metastatic colorectal cancer received alternating cycles of low immunomodulating doses of alpha-IFN + 5-Fluorouracil (5-FU) or 5-FU alone. Hematological, biochemical and physical evaluation showed that both treatment cycles were well tolerated. However, transient fever and moderate flu-like symptoms were observed following alpha-IFN administration. Treatment with 5-FU alone produced long-lasting inhibition of CD8+ T lymphocytes, but did not depress NK activity (NKA). Combined treatment with alpha-IFN produced a short-term increase of NKA and antagonized the effect of 5-FU on CD8+ cells on day 5 of the cycle. Parallel studies on in vitro models showed antiproliferative effects of 5-FU on PHA-stimulated MNC and confirmed the preferential inhibition of CD8+ cells. Pretreatment with alpha-IFN did not reverse the effect of 5-FU on CD8+ lymphocytes, but partially protected MNC from the toxic effects of the drug. This was presumably due to the cytostatic effects induced by alpha-IFN on MNC before exposure to the cycle-specific antineoplastic agent. This investigation suggests that alpha-IFN could play a positive role in immuno-chemotherapy of colorectal cancer through multiple mechanisms not entirely related to direct antitumor effects of the agent.

The generation of natural killer (NK) cells from NK precursor cells in rat long-term bone marrow cultures

In this report, we describe a novel long-term bone marrow culture (LTBMC) system to study the origin and generation of natural killer (NK) cells from NK precursors. Rat bone marrow was cultured for 4 wk in RPMI 1640 with 5% fetal calf serum and 2-mercaptoethanol to allow the formation of an adherent stromal cell layer containing NK precursor cells. After addition of interleukin 2 (IL-2), the LTBMC generated high numbers (up to 100-fold expansion in 7 d) of pure 3.2.3+ large granular lymphocytes with lytic activity against NK-sensitive and -resistant tumor targets, as well as antibody-dependent cellular cytotoxicity. NK activity in LTBMC could be detected 3 d after addition of as little as 1 U/ml rIL-2, whereas lymphokine-activated killer activity was found 5 d after addition of at least 10 U/ml rIL-2. In vivo depletion and in vitro complement lysis studies showed that the NK precursor cells in LTBMC did not express the NK-associated surface markers asialo GM1 or 3.2.3. We also found that LTBMC cells did not exhibit colony growth in granulocyte/macrophage or spleen colony-forming unit assays. The generation of NK cells from NK precursors required, in addition to IL-2, a second growth/maturation factor(s), which was present in the conditioned medium of the LTBMC. This LTBMC system provides a unique in vitro model to study the development of NK cells from precursor cells, the role of the bone marrow stromal microenvironment in this development, and the lineage relationship of NK cells to other hematopoietic cells.

Vaccination against polyoma virus (PyV) tumors using vaccinia-PyV recombinants: a major tumor-specific transplantation antigen (TSTA) epitope resides within the C-terminal segment of middle-T protein

We previously reported that inoculation of rats with live vaccinia virus (VV) recombinants VVpyMT, VVpyLT expressing either the middle-T (MT) or large-T (LT) proteins of polyomavirus (PyV) can elicit immunity to challenge with syngeneic PyV-tumor cells. We now report the results of cross-vaccination studies. VVpyMT was ineffective against cells expressing LT protein but prevented development of MT-expressing cells. Conversely, the VVpyLT was ineffective against MT-expressing cells. In the two experiments performed, tumor growth enhancement rather than retardation was observed in VVpyLT-vaccinated animals receiving PyV-LT (FRLTI) challenge tumor cells. To determine the location of the major TSTA within MT, a further VV recombinant (VVpyMT/Cfr) was constructed that expresses only the unique C-terminal segment of MT. VVpyMT-Cfr and VVpyMT were equally effective in eliciting tumor immunity, indicating the presence of a major TSTA epitope within the unique C-terminal region of MT.

In vivo treatment with monoclonal antibody 3.2.3 selectively eliminates natural killer cells in rats

We recently described a mAb 3.2.3 (IgG1), that recognizes a 60-kD dimeric molecule expressed exclusively on fresh and rIL-2-activated NK cells and polymorphonuclear cells. mAb 3.2.3 enhances cytolytic activity of NK cells against selected FcR+ tumor target cells by reverse antibody-dependent cellular cytotoxicity (ADCC), indicating that it recognizes an important triggering site on NK cells. The in vivo treatment of F344 rats with mAb 3.2.3 intraperitoneally completely and selectively eliminated NK/ADCC function in the spleen and peripheral blood for up to 10 d after treatment. Total numbers and percentages of T cells, monocytes, or PMN were not decreased and T cell function, as determined by Con A stimulation, was not affected. The reduction in NK function was associated with a decrease in the numbers of LGL and the expression of other NK-related cell surface markers including CD2, CD8, and asialo GM1. Depletion of NK cells with 3.2.3 markedly decreased the survival of F344 rats injected intravenously with MADB106 mammary adenocarcinoma cells, but did not affect the subcutaneous growth of MADB106 tumors. These results indicate that mAb 3.2.3 (in contrast to anti-asialo GM1 and OX8, which are less selective markers) will be useful for studies on the functional role of NK cells in vivo as well as their in vivo differentiation and origin from 3.2.3- precursors.

[Development of Eimeria tenella in MDBK cell culture with a note on enhancing effect of preincubation with chicken spleen cells]

Eimeria tenella, an intracellular protozoan parasite infecting the epithelial cells of the ceca of chickens, causes severe diarrhea and bleeding that can lead its host to death. It is of interest that E. tenella first penetrate into the mucosal intraepithelial lymphocytes (IEL) before they parasitize crypt or villous epithelial cells. This in vitro study was undertaken to know whether the penetration of E. tenella into such a lymphoid cell is a beneficial step for the parasite survival and development. Three sequential experiments were performed. First, the in vitro established bovine kidney cell line, MDBK cells, were evaluated for use as host cells for E. tenella, through morphological observation. Second, the degree of parasite development and multiplication in MDBK cells was quantitatively assayed using radioisotope-labelled uracil (3H-uracil). Third, the E. tenella sporozoites viability was assayed after preincubation of them with chicken spleen cells. E. tenella oöcysts obtained from the ceca of the infected chickens were used for the source of the sporozoites. Spleen cells (E) obtained from normal chickens (FP strain) were preincubated with the sporozoites (T) at the E:T ratio of 100:1, 50:1 or 25:1 for 4 or 12 hours, and then the mixture was inoculated into the MDBK cell monolayer. Morphologically the infected MDBK cells revealed active schizogonic cycle of E. tenella in 3-4 days, which was characterized by the appearance of trophozoites, and immature and mature schizonts containing merozoites. The 3H-uracil uptake by E. tenella increased gradually in the MDBK cells, which made a plateau after 48-60 hours, and decreased thereafter. The uptake amount of 3H-uracil depended not only upon the inoculum size of the sporozoites but also on the degree of time delay (preincubation; sporozoites only) from excystation to inoculation into MDBK cells. The 3H-uracil uptake became lower as the preincubation time was prolonged. In comparison, after preincubation of sporozoites with spleen cells for 4 or 12 hours, the 3H-uracil uptake was significantly increased compared with that of control group. From the results, it was inferred that, although the penetration of E. tenella sporozoites into the lymphoid cells such as IEL is not an essential step, it should be at least a beneficial one for the survival and development of sporozoites in the chicken intestine.

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.

Immune competence in 90Sr-exposed, adult thymectomized and antilymphocyteglobulin-treated CBA mice. I. Allogenic skin graft reaction

CBA mice subjected to either adult thymectomy, internal exposure to 90Sr or antilymphocyteglobulin treatment separately, or to combinations of the three were tested for cellular immune competence using their reaction to allogenic skin grafts. Peripheral blood white cell counts did not reveal any obvious correlation between the degree of mononuclear cell depletion and the ability to accept grafts, suggesting that the particular treatments depleted specific fractions of mononuclear cells, differing in their extent of involvement in the rejection process. No single treatment alone induced a significant prolongation in the time elapsed before graft rejection. Adult thymectomy followed by appropriate antilymphocyteglobulin treatment induced severe lymphocytopenia and a profound suppression of the cell-mediated immune system, as evidenced by the acceptance of allogenic skin grafts. When applied to 90Sr-preexposed mice the same treatment induced lifelong acceptance of grafts, indicating a similar, though weaker immunosuppressive impact of 90Sr. Hence it was possible to significantly enhance immunosuppression in 90Sr-exposed mice. This in vivo model should be useful when investigating the role of immunological responsiveness in radiation carcinogenesis.

Natural killer activity in Fischer-344 rat lungs as a method to assess pulmonary immunocompetence: immunosuppression by phosgene inhalation

Phosgene, also known as carbonyl chloride, carbon oxychloride, and chloroformyl chloride, is a toxic air pollutant and a potential occupational health hazard. Studies were initiated (a) to evaluate the measurement of pulmonary natural killer (NK) activity as a method to assess pulmonary immunocompetence, and (b) to determine whether exposure to phosgene resulted in local pulmonary or systemic immune dysfunction. Fischer-344 male rats were exposed either to filtered air or to 1.0 ppm phosgene gas for four hours. The effect of phosgene on lung NK activity was quantified at different times after acute phosgene exposure. Pulmonary NK activity was measured by mincing lung tissue into small pieces prior to incubation with collagenase. Whole-lung homogenate was assayed for NK activity utilizing a 4 hour 51-Cr-release assay with YAC-1 cells as target cells. Acute phosgene exposure resulted in a suppressed pulmonary NK activity on days 1, 2, and 4 after exposure; however, normal levels of biological activity were observed 7 days after exposure. The suppressed NK activity was not restored after removal of adherent cells from the lung homogenate, thus indicating that the effect of phosgene on NK activity was not due to immunosuppression via mobilization of suppressor alveolar macrophages. Pulmonary immunotoxicity was also observed after exposure at 0.5 ppm, while no adverse effects were observed at 0.1 ppm phosgene. Systemic immunotoxic effects were observed for NK activity in the spleen, but not in the peripheral blood. It is thus important in pulmonary immunotoxicology to evaluate systemic immune functions, since secondary effects--distant to the original interaction--may occur with potentially serious consequences. Cells exhibiting natural killer activity comprise a part of the nonspecific innate immunity that is important in defense against both neoplastic and viral diseases. Any perturbation of this important nonspecific immunological mechanism may result in a compromised host more susceptible to infectious and neoplastic disease.

The cellular immunotherapy of cancer: current and potential uses of interleukin-2

The potential for immune-mediated destruction of neoplasms was suggested nearly one century ago. Despite this, no "magic bullet" has yet been identified. Nevertheless, the physiology of cell-mediated immune reactions has been well characterized in molecular, cellular, and clinical studies of allograft and microbial immunity. Extensive studies performed in laboratory animal models have documented the in vitro and in vivo destruction of various neoplastic tissues by immune cells. This destruction can be directed against autologous, syngeneic, or allogeneic tumors in several systems with varying degrees of "tumor specificity". Two approaches exist towards utilizing these immune reaction in vivo. The first involves providing the tumor bearer with immunostimulatory agents, either specific or nonspecific, designed to activate and amplify the destructive potential of the individual's endogenous immune cells able to recognize and destroy autologous tumor. The second approach provides immune cells with antitumor capacity to a tumor-bearing individual, these cells having been activated exogenously. A number of successful regimens involving these two approaches, and combinations of them, have been delineated in animal tumor models. These experimental studies lay a strong foundation for initiating clinical trials of these concepts for patients with cancer. This review summarizes the diverse experimental studies in animals leading to clinical trials, presents recent data from ongoing clinical trials directly testing the potential for cellular immunotherapy, and then presents some of the major challenges facing further development and application of this potential therapeutic approach.

Inhibition of cell-mediated immunity by tumour cell products: depression of interleukin-2 production and responses to interleukin-2 by mouse spleen cells

Supernatants from cultures of mouse and human tumour cells inhibited the production of interleukin-2 (IL-2) by stimulated mouse spleen cells. The tumour cells tested, all of which were active, included a mouse and a human melanoma, three methylcholanthrene-induced fibrosarcomas of mice, and human HeLa cells. Supernatants from normal mouse and human fibroblasts were inactive. Inhibition was dose-dependent. Spleen cells from aged mice were more susceptible to inhibition than spleen cells from young mice. When tumour cell culture supernatants were fractionated on Sephacryl S-300, two peaks of activity were found, with apparent molecular weights of approximately 50 and 18 kD. Supernatants from tumour cell and fibroblast cultures caused variable, but generally weak, inhibition of responses of lymphoblasts to IL-2. It is suggested that inhibition of IL-2 production may be an important mode of action of tumour cell products that inhibit cell-mediated immunity.

Suppression of T-lymphocyte cytotoxicity following exposure to 60-Hz sinusoidal electric fields

A significant 25% inhibition (P less than .005) of allogeneic cytotoxicity of the target cell MPC-11 by the murine cytotoxic T-lymphocyte line CTLL-1 was observed when the 4-h cytotoxicity assay was conducted immediately following a 48-h pre-exposure of the effector lymphocytes to a 10-mV/cm (rms) 60-Hz sinusoidal electric field. At 1.0 mV/cm a significant 19% inhibition (P less than .0005) was seen. At 0.1 mV/cm a nonsignificant 7% inhibition of cytotoxicity was noted. When the 4-h cytotoxicity assay was conducted in the presence of the field using previously unexposed effector lymphocytes, cytotoxicity was not significantly reduced. Cell proliferation in the presence of interleukin-2 was unaffected by the field. These data suggest a dose response and threshold (between 0.1 and 1.0 mV/cm) for inhibition of cytotoxicity in clonal T-lymphocytes by exposure to a 60-Hz sinusoidal electric field. These results suggest mechanisms by which 60-Hz electric fields could affect the function of cells of the immune system.

Cell-mediated cytotoxicity in children during and after therapy for acute lymphoblastic leukemia

Cell-mediated cytotoxicity is considered to play a major role in immune defense and in particular in the killing of virus-infected and neoplastic cells. It appears to have some interesting implications when considering the infectious risk of acute lymphoblastic leukemia (ALL) children during immunosuppressive chemotherapy and the role of self-defense against minimal residual disease. We have studied natural killer (NK) activity and lymphokine-activated killer (LAK) activity in children during and after treatment for ALL. We observed that peripheral blood mononuclear cells in 22 children undergoing maintenance chemotherapy displayed significantly depressed NK activity compared with normal controls even when the proportion of NK cells was normal. LAK activity was also considered in 43 ALL children during and after maintenance chemotherapy. We observed that LAK activity was persistently comparable with that of normal controls. It seems definite that NK activity impairment is transient and is completely restored in ALL children a few months after chemotherapy has been successfully completed. The evidence that LAK activity is not impaired in ALL children may have some implications in view of a possible immunomodulatory approach in the presence of refractory disease.

T-cell tumor elimination as a result of T-cell receptor-mediated activation

It has recently been shown that activation of murine T-cell hybridomas with antigen inhibits their growth in vitro. The "suicide" of these neoplastic T cells upon stimulation with antigen suggested the possibility that activation via the antigen-specific receptor could also inhibit the growth of neoplastic T cells in vivo. To test this, mice were subcutaneously inoculated with antigen-specific T-cell hybridomas and then treated intraperitoneally with antigen. Administration of the appropriate antigen immediately after inoculation with the T-cell hybridoma abrogated tumor formation; antigen administered after tumors had become established decreased the tumor burden and, in a substantial fraction of animals, led to long-term survival. The efficacy of antigen therapy was due to both a direct inhibitory effect on tumor growth and the induction of host immunity. These studies demonstrate the utility of cellular activation as a means of inhibiting neoplastic T-cell growth in vivo and provide a rationale for studying the use of less selective reagents that can mimic the activating properties of antigen, such as monoclonal antibodies, in the treatment of T-cell neoplasms of unknown antigen specificity.

Tumour prevention and rejection with recombinant vaccinia

Tumour-specific antigens (TSA; ref. 1) have been exploited in the diagnosis and imaging of human cancer and anti-TSA antibodies have therapeutic potential. Vaccination with TSA or anti-idiotypic (TSA) antibodies has also been used to control tumour growth in model systems. An effective immune response nevertheless demands copresentation of antigen with host histocompatibility determinants. We therefore examined whether live vaccinia virus recombinants expressing TSA in cells of the vaccinated host might better elicit tumour immunity. Polyoma virus (PY) is tumorigenic in rodents; because killed PY-transformed cells can elicit tumour immunity, a PY-specific TSA has been postulated. Tumorigenesis involves expression of three early PY proteins, large-T (LT), middle-T (MT) and small-T (ST), but their role as TSAs is unclear. We therefore expressed the three T proteins in separate vaccinia recombinants. Rejection of PY tumours was observed in rats immunized with recombinants expressing either LT or MT. Further, tumour-bearing animals could be induced to reject their tumours by inoculation of recombinants.

The role of tumor-specific Lyt-1+2- T cells in eradicating tumor cells in vivo. II. Lyt-1+2- T cells have potential to reject antigenically irrelevant (bystander) tumor cells on activation with the specific target tumor cells

The present study investigates some of mechanisms for tumor-specific Lyt-1+2- T cell-mediated tumor cell eradication in vivo through analyses of tumor specificity in the afferent tumor recognition and efferent rejection phases. When C3H/He mice which had acquired immunity against syngeneic MH134 hepatoma were challenged with other syngeneic X5563 plasmacytoma cells, these mice failed to exhibit any inhibitory effect on the growth of X5563 tumor cells. However, the inoculation of X5563 tumor cells into the MH134-immune C3H/He mice together with the MH134 tumor cells resulted in appreciable growth inhibition of antigenically distinct (bystander) X5563 tumor cells. Although the growth of X5563 cells was inhibited in an antigen-nonspecific way in mice immunized to antigenically unrelated tumor cells (bystander effect), the activation of Lyt-1+2- T cells leading to this effect was strictly antigen-specific. Such a bystander growth inhibition also required the admixed inoculation of the bystander (X5563) and specific target (MH134) tumor cells into a single site in mice immunized against the relevant MH134 tumor cells. Furthermore, the results demonstrated that Lyt-1+2- T cells specific to MH134 tumor cells were responsible for mediating the growth inhibition of antigenically irrelevant (bystander) and relevant tumor cells. These results are discussed in the context of cellular and molecular mechanisms involved in the Lyt-1+2- T cell-initiated bystander phenomenon.

Increased macrophage activity in protein A treated tumor regressed animals

Male swiss albino mice transplanted with 1 x 10(6) viable fibrosarcoma tumor cells were treated with Protein A (60 micrograms/kg) right from the day of transplantation for 4 weeks, twice weekly. The therapy resulted in lesser tumor incidence, significant inhibition of tumor growth and enhanced percent survival in treated animals as compared to untreated controls. Treated animals also showed gains in body weight, an increase in peripheral blood leucocyte count, significant increase in macrophage function and number. Stimulation of macrophage number and macrophage function by Protein A may be related to its antitumor.

Effect of immunotherapy with a saline phenol extract of allogeneic tumour on E-rosette counts in horn cancer-affected cattle

The mean percentage of cells forming rosettes with 2-aminoethyl isothiouronium bromide-treated sheep erythrocytes (EAETRFC) in the peripheral blood of 10 horn cancer-affected cattle (40.05 +/- 2.91) was significantly low in comparison to the value in unaffected control animals (58.61 +/- 1.68). Immunotherapy with a saline phenol extract of allogeneic tumour tissue resulted in a gradual increase in the mean percentage of EAETRFC on each subsequent week. The increase was statistically significant from the second week onwards and on the sixth week, the percentage of EAETRFC in horn cancer affected cattle (56.80 +/- 1.38) closely approximated the value in unaffected controls.

Dietary fat and neoplasia--the role of net energy in enhancement of carcinogenesis: effects of fat and calories on the immune system

The mechanism by which carcinogenesis is enhanced by dietary fat is not understood. We know that a minimum level of essential fatty acids (EFA) is necessary for mammary tumor development and that this level probably exceeds the normal requirements of rats. Once the minimum level of EFA has been supplied, the calorie contribution of dietary fat may account for its enhancement of carcinogenesis. In this regard, we must recognize that the efficiency with which dietary energy is utilized is known to increase as the fat content of the diet is raised. Hence even when fed isocalorically to low fat diets, high fat diets will provide more net energy. Modulation of host immunity has been proposed as a mechanism of action of both fat and calorie intake on neoplasia. We review the literature examining the effects of fat and calories on the cell-mediated immune system, that arm of the immune system most directly responsible for the killing of neoplastic cells.

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.

Monoclonal antiidiotypic antibodies related to a murine oncofetal bladder tumor antigen induce specific cell-mediated tumor immunity

Rat monoclonal antibody 6.10 recognizes a 175-kDa protein expressed in all BALB/c mouse transitional cell bladder carcinomas tested, in epithelial cells of the mouse embryo, and in a few epithelial cells of adult mice. The antibody was used as an immunogen to generate two mouse monoclonal antibodies, 21D9 and 43A10, which bind to idiotopes on antibody 6.10 associated with the binding site for the 175-kDa antigen. The antiidiotypic antibodies induced bladder tumor-specific, cell-mediated immunity when injected into syngeneic mice, as shown by delayed-type hypersensitivity reactions in vivo and leukocyte adherence inhibition reactions in vitro. Tumor specificity was demonstrated by employing as controls a chemically induced BALB/c fibrosarcoma, MCA-1511 (MCA, 3-methylcholanthrene), and its corresponding antiidiotypic antibody, 5.96. Lymphocytes from mice sensitized with antibody 21D9 or 5.96 specifically recognized antigens in extracts of BALB/c bladder carcinoma BTCC-1660 (BTCC, bladder transitional cell carcinoma) and sarcoma MCA-1511, respectively, as shown by leukocyte adherence inhibition reactivity. This reactivity was selectively abrogated by prior treatment of the sensitized cells with the appropriate antiidiotypic antibodies and complement. An antigen recognized in vitro by antibody 21D9-sensitized lymphocytes could be separated from BTCC-1660 extract by immunoabsorption with antibody 6.10 and elution with acidic buffer. Our findings indicate that the oncofetal antigen defined by antibody 6.10 is recognized by the immune system of syngeneic mice and suggest that antiidiotypic antibodies related to certain oncofetal antigens can be used to immunize against syngeneic tumors.

Immunotherapeutic studies of different clonal lines of herpesvirus-induced fibrosarcoma in a syngeneic rat

Transformation of White Buffalo rat embryonic cells by dye-light-inactivated herpesvirus type 2 resulted in the development of two clones of transformed cells (G2 and rat fibrosarcoma) with significantly different tumorigenic capabilities. The G2 cell line was initially nontumorigenic, while the rat fibrosarcoma line was very highly tumorigenic in rats. These significant differences in transformed cell clones from the same initial culture offered an opportunity to study aspects of the immunobiology of oncogenicity. The development of fibrosarcomas in immunoincompetent nude mice with the same early passages of the G2 cell line which were nontumorigenic in the immunocompetent rat suggested that immunologic resistance developed more effectively in the competent host against the G2 line than against rat fibrosarcoma cells. Syngeneic rats which were first exposed to the early passage nontumorigenic G2 cells were completely protected against tumor development by the rat fibrosarcoma cell lines. In subsequent in vitro passages of the G2 cell line, it lost its ability to protect against rat fibrosarcoma challenge and gradually became oncogenic in rats. Modification of antigenic exposure, accomplished by treating the G2 cells with cholesteryl hemisuccinate, resulted in an increase in the protection by these cells and a delay in tumor development.

Prospectively randomized trial of adjuvant active-specific immunotherapy for human colorectal cancer

Over the last four years a guinea pig model of active-specific immunotherapy (ASI) with a syngeneic tumor cell:bacillus calmette-Guerin (BCG) vaccine was translated into a prospectively randomized, controlled clinical trial in patients with colorectal cancer. Primary tumors from patients undergoing standard surgical resection were dissociated enzymatically and cryopreserved by techniques that maintain cell viability. Patients with transmural extension of tumor or nodal metastases were randomized into groups treated by resection alone (control) or resection plus ASI. With a mean follow-up of 28 months (range, 14-24), only 3 of 20 treatment patients had recurrences and none have died, whereas 9 of 20 control patients had recurrences and 4 died. These differences are statistically significant and are sufficiently encouraging to warrant expansion of these studies into other research centers.

Natural killer cells

It is proposed that this article will encompass a review of primarily the human natural killer cell. The following parameters of the human natural killer (NK) cell will be reviewed: its ontogeny; surface membrane characteristics including monoclonal antibody reactivity, cell lineage, the natural killer sensitive targets, and the proposed mechanism of action of natural killer cells cytotoxicity against these NK sensitive targets; the status of natural killer cell in relationship to clinical disease; the alteration of natural killer cells both in vitro and in vivo; and finally postulate relevance of the natural killer cell in context of the evolution or pathophysiology of human disease. There will be an attempt through this review to encompass the more recent publications that pertain to the various sections.

Immunosuppressor control as a modality of cancer treatment: effect of plasma adsorption with Staphylococcus aureus protein A

In tumor-bearing hosts both cellular and humoral tumor-growth-enhancing factors are present. They cause immunosuppression and facilitate the growth of tumors. Very early during tumor growth these factors are either elicited by the tumor cells or induced by the host immunocytes. Among these immunosuppressive agents, circulating immune complexes appear to play a predominant role. They also activate suppressor cell activity. Plasma adsorption of CIC and IgG by protein A of Staphylococcus aureus has been reported to cause tumor regression. Plasma adsorption with protein A-collodion charcoal, protein A-silica, or protein A-Sepharose also induced tumorilytic reactions. Even direct infusion of protein A induced tumor regressions in rat mammary tumors. Recent studies showing tumor regressions following S. aureus Wood 46 plasma adsorption or infusion of normal plasma adsorbed over S. aureus indicate that specific blocking factor removal by plasma adsorption may not be the mechanism for causing tumor destruction. Results indicate that S. aureus plasma adsorption leaches a number of staphylococcal agents. Thus, it appears that staphylococcal agents, protein A, enterotoxin, and other factors are responsible for the induction of reactions leading to tumor destruction. A unified mechanism explaining the results obtained with plasma adsorption using protein A of S. aureus, or S. aureus Wood, or direct protein A infusion, was presented.

Characterization of tumor-induced inflammation and the effect of some anti-inflammatory drugs on the increased vascular permeability

The vascular bed in a murine dermal tissue responded to inoculated tumor cells by two-phased changes in the vascular permeability. The initial increase in the vascular permeability was seen in an early stage (1 to 3 day post tumor cells inoculation), and the inflammation was sensitive to glutathione (GSH). Glucocorticoids reduced the increased vascular permeability, but neither acetylsalicylic acid nor indomethacin did. The later vascular response was produced by a growing solid tumor in a continuous mode beginning at 5th to 10th day post inoculation. The degree of the increased vascular permeability in this chronic phase was in direct proportion to the wet weight of the solid tumor, and the inflammation was insensitive to glutathione. Glucocorticoids reduced the increased vascular permeability, but neither acetylsalicylic acid nor indomethacin did. The action of glucocorticoids on the tumor-induced vascular hyper-permeability was discussed in connection with a tumor factor possibly responsible for the vasoexudation.

Tumour regression after extracorporeal affinity chromatography of blood plasma across agarose beads containing staphylococcal protein A

The therapeutic effect of absorbing plasma from tumour patients with immobilized staphylococcal protein A was tested. Plasma prepared by centrifugation was passed over protein A-Sepharose and then reinfused into the patient. Five patients were thus treated. One with malignant melanoma and one with renal adenocarcinoma showed measurable regression of metastatic lesions. In another with malignant melanoma a subcutaneous metastasis showed histopathological changes compatible with a therapeutic effect. In two patients, one with malignant melanoma and one with renal adenocarcinoma, no signs of regression were found. No severe adverse effects of the treatment were observed.

Mitomycin C-treated or irradiated concanavalin A-activated T cells augment the activation of cytotoxic T cells in vivo

The activation of cytotoxic T lymphocytes (CTL) in vivo after immunization of normal or cyclophosphamide-treated mice with allogeneic cells was strongly augmented by the administration of mitomycin C-treated or irradiated concanavalin A-activated spleen cells (Con A-spl). This effect of the Con A-spl was abrogated by treatment with Anti-Thy 1 antibody plus complement, and was therefore presumably mediated by activated "helper" T cells. (The term "helper" cell is only operationally defined in this context and indicates that the augmenting irradiation resistant T cells are obviously not CTL precursor cells). These observations indicated (i) that even the cytotoxic response against allogeneic stimulator cells suffers in vivo from insufficient "helper" T cell activity, and (ii) that the injection of Con A-spl may serve as a simple procedure to apply this "helper" activity in vivo. This procedure was at least as effective as the repeated injection of interleukin 2 (IL-2)-containing cell supernatants with up to four 30-unit doses of IL-2 per mouse. IL-2-containing cell supernatants were found to mediate similar effects only if injected into the footpads but not intravenously. This was in line with the reported observation that IL-2 has an extremely short half-life in vivo. The injection of Con A-spl was also found to augment the proliferative response in the regional lymph nodes.

The augmentation of tumor-specific immunity by virus help. II. Enhanced induction of cytotoxic T lymphocyte and antibody responses to tumor antigens by vaccinia virus-reactive helper T cells

The present study investigates the role of vaccinia virus-reactive helper T cells in causing enhanced induction of syngeneic tumor immunity. Vaccinia virus-reactive helper T cell activity capable of inducing the augmented generation of cytotoxic T lymphocyte (CTL) or antibody responses was generated in C3H/HeN mice by inoculating i.p. live virus. Immunization of these mice with vaccinia virus-infected syngeneic X5563 plasmacytoma or MH134 hapatoma cells led to augmented induction of immune resistance against the challenge with corresponding viable tumor cells when compared with the incidence of resistance observed in control mice not primed to vaccinia virus. In vitro cytotoxicity tests utilizing spleen cells and serum from mice which resulted in the augmented tumor resistance by virus help have revealed that spleen cells from C3H/HeN mice immune to the X5563 plasmacytoma exhibited appreciable anti-X5563 CTL activity, whereas serum from these mice failed to display any antibody response. In contrast, MH134-immune mice exhibited potent anti-MH134 antibody, but not CTL responses. Such an anti-tumor CTL or antibody response augmented by vaccinia virus-reactive helper T cells was found to be tumor specific. These results are discussed in the context of (a) the functional diversity of tumor antigens, and (b) mechanisms of virus help that are involved in various forms of augmented induction of syngeneic tumor immunity.

Human lymphocyte function-associated antigens

Three cell surface molecules, designated LFA-1, LFA-2, and LFA-3 were identified by mAbs selected for their ability to block cytolysis by an OKT4+, HLA-DR-specific CTL line. The LFA mAbs block all CTL and proliferative functions studied. In addition, anti-LFA-1 mAbs inhibit NK-mediated cytolysis. By analogy with murine LFA-1, human LFA-1 may be involved in the adhesion stage of cellular interactions. LFA-2, the SRBC receptor molecule, appears to be a T cell function-specific molecule. We have not yet established whether LFA-2 participates in antigen recognition or whether it is involved in antigen-non-specific interactions. The anti-LFA-3 mAb specifically blocks function by binding to the target cells, implying that LFA-3 may be a target ligand for an effector-specific receptor. The CTL-target interaction involves a number of steps, including antigen recognition, cell adhesion, and delivery of the lethal hit [22]. The LFA antigens show the complexity of this process at the molecular level. The anti-LFA monoclonal antibodies will be useful probes into the T cell immune response and may prove clinically relevant, both diagnostically and therapeutically.