In vitro inhibition of lymphoproliferative responses to tumor associated antigens and of lymphoma cell proliferation by rat splenic macrophages

Bacterial agents protect against autoimmune disease. I. Mice pre-exposed to Bordetella pertussis or Mycobacterium tuberculosis are highly refractory to induction of experimental autoimmune encephalomyelitis

Infectious agents have often been implicated in the etiology of autoimmune diseases. Here we show that bacteria may also play a role in resistance to autoimmune diseases. SJL/J and (SJL/J x BALB/c)F1 mice are genetically susceptible to induction of experimental autoimmune encephalomyelitis (EAE), a murine model for human demyelinating autoimmune diseases such as multiple sclerosis. We studied the effect of several bacteria on the development of EAE and found that exposure of SJL/J or (SJL/J x BALB/c)F1 mice to Mycobacterium tuberculosis or Bordetella pertussis consistently rendered mice highly refractory to subsequent induction of the disease. Other bacteria such as Escherichia coli, Shigella and Staphylococcus aureus were found to be less effective, or were protective only if specific immunization procedures were used. Furthermore, M. tuberculosis and B. pertussis were protective irrespective of the route of administration and minute amounts (as low as 0.5 micrograms) of M. tuberculosis were sufficient to protect EAE-susceptible mice against induction of the disease. Interestingly, these bacteria, which are commonly used to promote development of EAE, conferred the highest degree of protection against the disease. The M. tuberculosis-induced protection was found to be associated with active suppression mechanisms mediated by T lymphocytes capable of transferring protection to naive syngeneic mice. These findings indicate that certain bacteria may protect against the development of autoimmune diseases. These results also suggest the potential use for still-unidentified bacterial agents in the manipulation of certain autoimmune diseases.

Identification of a novel cell population in nonhealing wounds in tumors

We have explored wound healing in tumors as a possible model for tumor-host interaction. This work demonstrated tumor wound healing failure to be the result of intense inhibition of fibroblasts although the tumor cells did not appear to be the direct source of the inhibitors. The inflammatory infiltrate found in tumor wounds was then examined for possible sources of the observed fibroblast suppression. Although the tumor wound infiltrate contains cell populations similar to a normal wound infiltrate, it also contains a large, vacuolated, nonadherent, phagocytic mononuclear cell which has morphologic and cytochemical characteristics of a lipid-laden macrophage. However, the cell also proliferates under normal culture conditions and has an immunophenotype more characteristic of lymphocytes than those of macrophages with striking expression of the CD8 surface antigen. Conditioned media from this cell population markedly inhibit fibroblast proliferation suggesting it is the source of fibroblast inhibitors within the tumor wound. Mechanical dissociation of non-wounded tumors yielded evidence that the tumor wound cell is normally present in small numbers within the tumor.

Suppression of experimental allergic encephalomyelitis by MBP-coupled lymphoid cells and by MBP-liposomes: a comparison

In previous experiments, we showed that administration of myelin basic protein (MBP) inserted into phosphatidyl-serine liposomes, to susceptible animals suppressed the clinical manifestations of both acute and chronic-relapsing EAE. In this report we compare the effectiveness of treatment with MBP-liposomes and with MBP-coupled syngeneic spleen cells in EAE protection. Lewis rats treated with 150 micrograms MBP-liposomes or with 160 micrograms (35 x 10(6] MBP-coupled spleen cells, given 7 days before and 7 days after encephalitogenic challenge were equally protected against clinical EAE, when compared to untreated controls. In addition to clinical protection, in vitro proliferative responses of lymphocytes from treated rats were significantly reduced, but delayed hypersensitivity (DTH) reactions remained unaffected. Proliferation of lymphocytes from MBP-sensitized donors was inhibited by the addition of spleen cells but not of lymph node cells from treated donors. The inhibitory effect was observed with spleen cells regardless of whether the donors were treated or not, was antigen nonspecific, and localized in a radio-resistant, adherent cell population. Adoptive transfers of spleen cells from treated donors, after a 48-hr in vitro incubation with concanavalin A, showed that the cells from donors treated with MBP-coupled spleen cells, but not with MBP-liposomes, suppressed the disease in recipients, following challenge with MBP-complete Freund's adjuvant (CFA). These results suggest that two distinct mechanisms operate in the protection by MBP-coupled cells and MBP-liposomes, respectively.

Modulation of lectin-stimulated lymphocyte agglutination and mitogenesis by estrogen metabolites: effects on early events of lymphocyte activation

Pharmacological doses of estrogens such as 17-beta estradiol (17-beta E) and diethylstilbestrol (DES) suppress cell-mediated immunity in vivo. In this report, we investigated the direct in vitro effects of 17-beta E and its major metabolites on lymphocyte proliferation in response to the T cell lectin phytohemagglutinin (PHA). PHA-induced lymphocyte agglutination, an early event indicative of active, cytoskeletal-dependent membrane alterations, was monitored in conjunction with blastogenesis. Without exception, the effects of individual estrogen metabolites on the PHA-induced agglutination occurring within minutes were accompanied, at every concentration of compound, by equivalent effects on the blastogenic response of activated cells measured after several days. This observation suggested a role for estrogens in modulating lymphocyte activation at the cell surface rather than through cytosolic receptor-mediated events. As suggested by previous studies with quinone metabolites of benzene, the catechol estrogen metabolite 2-OH estrone (2-OH E) was significantly more potent than the parent compound at suppressing lymphocyte proliferation in vitro and in vivo.

Activation of suppressor T cells by low-molecular-weight factors secreted by spleen cells from tumor-bearing mice

The spleens of mice bearing large M-1 fibrosarcomas have been shown to contain several populations of cells which nonspecifically suppress antibody synthesis by cocultured normal spleen cells. It has now been shown that the spleens of tumor-bearing mice also contain inducer cells which secrete soluble factors capable of activating suppressor T cells from unprimed precursor cells. The activated suppressor cells are Thy 1+, Lyt 1+2+ and secrete a soluble suppressive factor. They inhibit the in vitro generation of antibody-forming cells by cocultured normal spleen cells stimulated by T-cell-dependent antigens. They do not, however, suppress the antibody response to T-cell-independent antigens and do not inhibit antibody synthesis by cocultured nude mouse spleen cells cultured with T-cell-dependent antigens and exogenous helper factors. In addition, suppression is blocked if conditioned medium containing T-cell growth factors is added to the suppressor cell assays. These data suggest that cells in the spleens of tumor-bearing mice secrete inducing factors which activate suppressor cells. These activated suppressor cells in turn secrete soluble suppressor factors which inhibit antibody synthesis, possibly by interfering with the synthesis or release of T-cell growth factors.

Isolation of immunogenic and suppressogenic glycoproteins from adenovirus type 12 hamster tumor cells

Two types of glycoproteins were isolated from the membrane fraction of adenovirus type 12 (Ad12) hamster tumor cells by recovering detergent-solubilized glycoproteins using concanavalin A-affinity chromatography and gel filtration. One of the glycoproteins consisted of a polypeptide of 130,000 daltons (130K) with a pI value of 4.7-5.1, and the other consisted of a polypeptide of 18,500 daltons (18.5K) with a pI value of 6.3-6.6. The glycoproteins were immunologically different. The 18.5K glycoprotein induced in vivo resistance to tumor growth and anti-tumor cytotoxic T cells, while the 130K glycoprotein induced in vivo suppressor T cells which inhibited the activity of anti-tumor cytotoxic T cells.

Infection-induced immunosuppression in pyelonephritis: characteristics of the suppressor cell(s)

Infection-induced suppressor cells may be associated with a depression of cell-mediated immune (CMI) mechanisms in pyelonephritis. In the present study, cell viability and cell to cell contact were established as prerequisites for immunosuppression and the role of mononuclear phagocytic cells and polymorphonuclear leukocytes, as immunoregulatory cells affecting CMI, was also examined. Fractionation of spleen cell suspensions was carried out using carbonyl iron, nylon wool, glass beads, and sephadex. These procedures restored mitogenic responsiveness to splenic lymphocytes from pyelonephritic animals, and it was possible to isolate cells with accessory and suppressor activity from nylon wool columns. Elutable cells (that is, cells which adhere to the column but could be recovered by the addition of EDTA) were characteristically accessory cells and increased the mitogenic responsiveness of normal lymphocytes. Adherent splenocytes which suppress mitogenic responses were isolated from pyelonephritic animals. Additionally, neutrophils, at concentrations readily demonstrable in lesions, depressed CMI responses in vitro. With this information available it should now be possible to carry out a detailed analysis of the cellular mechanism by which CMI in renal infection is depressed.

Deficient T-cell mitogen response in murine experimental autoimmune myasthenia gravis: a defect in the adherent cell population

T-Lymphocyte number and functions are often reduced, while B-lymphocyte function is often increased in patients with autoimmune disorders. To study the mechanisms responsible for these T-cell malfunctions in autoimmunity we adapted the murine experimental autoimmune myasthenia gravis (EAMG) model. Splenocytes from C57BL/6 mice immunized with acetylcholine receptors (AChR) in complete Freund's adjuvant (CFA) produced approximately half the amount of concanavalin A (Con A)-induced interleukin 2 (IL-2) as did splenocytes of CFA-inoculated controls. Further, AChR plus CFA-immunized splenocytes showed a marked reduction in T-cell proliferative responses induced by Con A or phytohemagglutinin when compared with CFA-inoculated controls. By contrast, lipopolysaccharide-induced B-cell function is preserved. Deficient Con A splenic T-cell response is seen early after secondary inoculation with CFA or AChR in CFA. T-Cell recovery occurs in CFA-inoculated mice but not in AChR plus CFA-inoculated mice. Defective Con A splenic T-cell response seen early after secondary immunization with CFA or AChR in CFA is due to the presence of a defective splenic adherent cell population. Moreover, defective Con A splenic T-cell response seen after established autoimmunity to AChR in EAMG is also due to the presence of a defective splenic adherent cell population.

Modulation of mitogen-induced proliferation of autologous peripheral blood lymphocytes by human alveolar macrophages

Experiments were carried out to determine the effect of cocultivation of T-cell-enriched human peripheral blood lymphocytes with autologous alveolar macrophages on mitogen-induced proliferation as determined by [(3)H]thymidine uptake. Cells obtained by fiberoptic bronchoscopy and saline bronchial lavage from 14 normal volunteers were enriched for macrophages by adherence in plastic dishes for 1 h in RPMI 1640 medium supplemented with 10% fetal calf serum. Nonadherent mononuclear cells were prepared from heparinized venous blood after Ficoll-Hypaque sedimentation by passage over nylon wool columns. T-cell-enriched populations were incubated with and without alveolar macrophages, either in the presence or absence of phytohemagglutinin. In these experiments, the number of lymphocytes was held constant (10(5) per well), while the number of alveolar macrophages was varied (0.1 x 10(5) to 4.0 x 10(5) per well). Alveolar macrophages generally tended to stimulate phytohemagglutinin-induced lymphoproliferation at lymphocyte/macrophage ratios of 10:1 but consistently and significantly suppressed proliferation at ratios which approach those usually observed in recovered human bronchial lavage fluid, namely, 1:4. The suppressive effect of alveolar macrophages was observed as early as 48 h after culture initiation, while the magnitude of suppression increased with time. Suppression did not appear to be due to alteration in lymphocyte viability, nor was it sensitive to indomethacin. These results indicate that human alveolar macrophages can modulate the in vitro proliferative response of autologous peripheral blood lymphocytes. This observation may have relevance to interactions between alveolar macrophages and bronchial lymphocytes in the human lung in vivo.

Psychosocial factors and psychophysiological mechanisms in the aetiology and development of cancers

Socio-cultural factors which may play a contributory role in the aetiology of cancer have been extensively investigated and it is well established that the incidence rates of different forms and sites of the disease are not equally distributed throughout the population. Social class, occupational, environmental and 'life-style' differences, amongst others, have been found to be associated with an excess risk of cancer, although the argument concerning the relative importance of these various factors remains a controversial one. It seems increasingly clear however, that there are large behavioural components which govern exposure to potential carcinogens and there is growing interest in the extent to which social and psychological demands may be associated with these agents or may operate as contributory factors in their own right. A number of early studies of psychological approaches to the study of cancer aetiology are reviewed from a methodological perspective. Much of the early work suffered from the problem that psychological characteristics of individuals who already had cancer were used to construct models concerned with aetiological factors. A number of the more recent studies which have attempted to overcome these difficulties are discussed. Tentatively, these later investigations suggest that two main groups of factors are related to an increased risk of cancer. First, the loss of, or lack of closeness or attachment to an important relation (often a parent) early in life, and second, the inability to express hostile feelings or more generally the abnormal release of emotion. Several psychophysiological mechanisms are reviewed which have attempted to account for the relationship between psychological disturbances and the onset of cancer, particularly the growing evidence which implicated a role for the immune system as a link between the central nervous system and disease processes.

Lymphocyte subpopulations and responsiveness in rats bearing intracranial tumors induced by avian sarcoma virus

The mitogenic responsiveness of peripheral blood lymphocytes obtained from Fischer 344 rats inoculated with avian sarcoma virus was studied. In addition, quantitative alterations in lymphocyte subpopulations were determined in these animals. Only peripheral blood lymphocytes from rats bearing astrocytomas had significantly diminished responses to concanavalin A when compared to control responses. The percentage of lymphocyte subpopulations detected in either the peripheral blood or spleen of tumor-bearing rats did not differ from values obtained with control rats. However, rats bearing astrocytomas had a marked decrease in the absolute number of the various lymphocyte subpopulations as a result of lymphopenia. Neither the sarcoma-bearing rats nor the virus-inoculated rats that did not develop tumors exhibited this lymphopenia. In addition, sera from rats bearing astrocytomas diminished the concanavalin A reactivity of spleen cells obtained from normal rats. The results of this study establish the avian sarcoma virus-induced rat astrocytoma model as a useful immunological parallel for the human disease.

In vitro suppression of T-cell mitogenic response and tumor cell proliferation by spleen macrophages from normal chickens

Adherent cells isolated from spleen of normal specific pathogen-free chickens inhibited mitogen-induced blastogenesis of autochthonous, syngeneic, or allogeneic lymphocytes. The adherent cells were also inhibitory to in vitro proliferation of cells of a rapidly dividing tumor line, MDCC-MSB-1, derived from a lymphoma induced by Marek's disease virus. The effector cell of suppression of both lymphoprolifrative functions appeared to be a macrophage because the suppressive activity of adherent cells could be abrogated by pretreatment with carrageenan but not with antisera specific to chicken T or B cells. The proportion of macrophages needed for effective suppression was substantially higher than the proportion of macrophages ordinarily present in spleen of normal, unstimulated chickens. This heretofore unrecognized suppressive capability of normal, presumably resting macrophages have been detected in certain infections.

Effector and enhancing lymphoid cells in plasmacytoma-bearing mice. II. Dynamic changes during tumor progression

The Winn assay was used for the study of effector (tumor-inhibiting) and enhancing (tumor-promoting) lymphoid cells in BALB/c mice bearing MOPC-104E plasmacytomas. Kinetic studies with thymus, lymphnode, spleen and bone-marrow cells revealed that spleen, lymph node and to a lesser extent bone-marrow cells from 7- and 10-day tumor-bearers inhibited MOPC-104E growth, while at day 13 all three cell populations enhanced tumor growth. However, at day 16 strong tumor inhibition was observed again by spleen cells and to a lesser extent by lymph-node cells and thymocytes. Peritoneal cells from normal and tumor-bearing (7 and 10 days) animals enhanced tumor growth significantly. Separation of spleen cells on nylon wool columns showed that at 10 days the effector cells were T lymphocytes, but at a later stage (35 days) a different effector mechanism was present in the spleen. Treatment of MOPC-104E recipients with carrageenan or silica had little influence on tumor growth, but marked tumor inhibition occurred after lethal irradiation and bone-marrow reconstitution. This latter observation, together with the finding that bone-marrow, lymph node and peritoneal cells from normal donors enhanced tumor growth in several experiments, suggests that this plasmacytoma, like hormone-dependent tumors, requires lymphocyte-derived growth factors.

Augmentation of cell-mediated cytotoxicity to a rat lymphoma. I. Stimulation of non-T-cell cytotoxicity in vivo by tumour cells

The injection of a syngeneic Gross-virus-induced lymphoma into W/Fu rats induced peaks of cytotoxicity in the spleen attributable to non-T cells and T cells 3 and 10 days later, respectively. The conditions required for augmenting the cytotoxicity of the non-T cells in various lymphoid compartments (shown elsewhere to closely resemble NK cells) were analysed using the ip and iv routes of inoculation and a variety of tumour cells including those normally susceptible or resistant to lysis by NK cells in vitro. Using an ip inoculation of W/FuG-1 cells (a tumour susceptible to lysis by NK cells), a short-lived, 3-fold increase in cytotoxicity was observed in the spleen at day 3 and a 5-fold increase in the PEC at day 5. Cytotoxicity in other lymphoid organs remained unchanged. Tumours resistant to lysis by NK cells also stimulated cytotoxicity in the spleen or PEC, although the effect depended on the dose and route of inoculation used, and depression of cytotoxicity was observed under some conditions.

Increased monocyte-mediated cytostasis of lymphoid cell lines in breast and lung cancer patients

Peripheral blood mononuclear cells of most normal adults and patients with breast or lung cancer were found to inhibit [3H] thymidine uptake by lymphoid cell lines in a growth inhibition assay. At effector:target cell ratios between 5:1 and 20:1, lung cancer patients and breast cancer patients, when compared to normal individuals, demonstrated significantly greater inhibition of [3H] thymidine uptake by a human lymphoid cell line (F-265). The effector cells were adherent and were probably monocytes. Sephadex G-10 column passage or adherence to plastic removed most growth-inhibitory activity. Adherent cells recovered from plastic flasks (88-94% monocytes) were strongly growth-inhibitory. Lung cancer patients receiving BCG immunotherapy were found to have an apparently increased activity compared to patients not treated with BCG. The possible mediation of the growth inhibition by release of prostaglandins was suggested by the reduced cytostatic effects in the presence of indomethacin. Growth-inhibitory activity was not species-restricted, since human effector cells and also effector cells from tumor-bearing mice were reactive against the human target cell and against a murine lymphoma line (RBL-5). Natural killer (NK) cells did not appear to contribute appreciably to the observed cytostasis, since the levels of their activities did not correlate, and human NK cells are non-adherent and have little reactivity against F-265 or RBL-5. The inhibition of [3H]thymidine uptake by target cells was demonstrated to be a good reflection of actual inhibition of proliferation, since incubation of adherent cells from cancer patients with F-265 resulted in similar degrees of reduction in the number of target cells and in [3H] thymidine uptake.

Immune responses to weakly immunogenic virally induced tumors. II. Suppressive effects of the in vivo carried tumor YAC

Unprimed spleen cells from A and C57BL/6 mice could not produce cytotoxic responses to their syngeneic tumors: a Moloney virus-induced in vitro subline YAC-1 and a Rauscher virus-induced in vitro subline RBL5, respectively. Spleen cells from A and C57BL/6 mice immunized with YAC-1 OR RBL5 (which cross-react serologically) generated significant syngeneic cytotoxicities after cultivation in vitro. The in vivo carried tumor of A mice, unlike the in vitro sublines, could not stimulate a priming effect. In contrast, YAC stimulated the formation of suppressor cells in both A and C57BL/6 mice. The suppressor cells abrogated the priming effect of the syngeneic tumors, but not the priming effect of the allogeneic tumors. Furthermore, YAC did not suppress normal allogeneic anti-tumor responses. The theoretical and the practical implications of these studies are discussed.

Tumor-induced changes in T cell mitogen responses in rats: suppression of spleen and blood lymphocyte responses and enhancement of thymocyte responses

Concanavalin A (Con A) and phytohemagglutinin (PHA) responses of spleen and blood lymphocytes from tumor-bearing (TB) rats were found to be markedly depressed in 4 different models employing tumors of spontaneous origin. Removal of phagocytic cells from both spleen and blood lymphocyte suspensions led to a complete restoration of the responses, indicating that the decreased responses were not due to intrinsic defects in the lymphocytes. The reduction was shown to be due to the inhibitory effect of an increase in the percentage of phagocytic cells. In addition, TB induced an atrophy of the thymus and a decrease in the number of thymic lymphocytes, mainly due to severe lymphocyte depletion in the cortex. The cells that remained in the thymus exhibited increased responsiveness to PHA and Con A as compared to thymus cells from normal rats. Similar results were found in hydrocortisone acetate-treated rats, suggesting that TB leads to a decrease in nonresponsive, cortical corticosteroid-sensitive thymocytes.

Natural cell-mediated cytotoxicity in rats. II. In vivo augmentation of NK-cell activity

Natural cell-mediated cytotoxicity in rats as well as in mice has been shown to vary consistently with age, with peak levels detectable at 5-10 weeks. The levels of cell-mediated cytotoxicity against tumor cells could be augmented in strains of inbred rats with either high or low levels of natural reactivity, by IP injection of a variety of agents, including C. parvum, LCMV, KRV, and poly I:C. The specificity of the augmented cytotoxicity appeared to be the same as the specificity of natural killer cells which are found in normal rat spleen cells. Similarly, the cells mediating the augmented cellular cytotoxicity were small, non-adherent, esterase-negative lymphocytes with Fc receptors, as are rat NK cells. The kinetics and organ distribution of the augmentation of NK activity by poly I:C and C. parvum were compared and the kinetics were found to differ, with a shorter time course of augmented activity seen after inoculation with poly I:C. These data indicate that interferon may play a central role in the augmentation of NK activity in vivo.