The effect of gold salts on tumour immunity and its stimulation by Corynebacterium Parvum

Kupffer cells and liver metastasis. Optimization and limitation of activation of tumoricidal activity

Kupffer cells, tissue-fixed macrophages located in the sinusoids of the liver, represent the highest concentration of mononuclear phagocytes in the body. Their ability to act as scavengers of particulate material in the blood has given rise to speculation that they play a role in controlling hepatic metastases derived from blood-borne tumor cells. Circumstantial evidence for such a role has been obtained from animal studies where Kupffer cell function has been compromised or inhibited, and from anecdotal clinical observations. Current evidence suggests that Kupffer cells are capable of nonspecifically eliminating some circulating tumor cells from the circulation via phagocytosis. This surveillance mechanism would appear to be limited in capacity, and subject to a number of external factors. Recent studies have demonstrated that Kupffer cells can be activated to a tumoricidal state via the administration of biological response modifiers such as gamma interferon or muramyl peptides. The localization of liposomes within Kupffer cells after systemic administration has provided a considerable stimulus for the efficient targeting of macrophage-activating compounds to these cells. Such therapeutic intervention, while capable of inducing Kupffer cell tumoricidal activity in situ and inhibiting tumor growth, is limited with respect to the location of the tumor cells (sinusoidal versus parenchymal) and to the size of the metastatic nodule. Therapeutic intervention using liposomes containing macrophage-activating agents may only be of benefit in patients with minimal tumor load who are at risk for hepatic metastases, rather than those patients who already have clinically detectable liver tumors.

Antiinflammatory proteins associated with human and murine neoplasms

The immune mechanisms by which a host recognizes and destroys a growing tumor are undoubtedly complex and, as yet, incompletely understood. It is apparent, however, that mononuclear phagocytes play an important role in the defense against neoplastic disease and that the ability of monocytes and macrophages to accumulate at and within a growing tumor is a strict requirement for them to effect that role. Studies from our laboratory as well as those of other investigators have demonstrated that patients with a variety of neoplastic diseases have a specific defect in monocyte chemotactic responsiveness and that this defect is associated with the presence of the tumor. Furthermore, we and others have shown that a similar defect occurs in tumor-bearing rodents, thus allowing model systems to be developed for the study of the mechanisms involved. We have demonstrated that transplanted, spontaneous or carcinogen-induced murine tumors produce low molecular weight proteins which inhibit the accumulation of macrophages to inflammatory foci and that a significant portion, if not all, of these proteins are physicochemically and antigenically related to the retroviral envelope protein p15E. We have shown that p15E itself can inhibit the inflammatory accumulation of macrophages in normal mice. Studies on a wide variety of cancer patients have revealed that the fluids of such patients contain proteins which inhibit the responses of normal monocytes to various chemotaxins and, as in tumor-bearing mice, that these antiinflammatory proteins are antigenically related to retroviral p15E. Recent studies have demonstrated that human tumor cells can simultaneously release factors which are chemotactic for monocytes with those which are p15E-related inhibitors of chemotactic responsiveness, suggesting that the mononuclear phagocyte response to a growing tumor may be, in part, dictated by the balance obtained between various proteins produced by that tumor. The isolation and characterization of endogenous retroviral sequences within the human genome and the observation that the envelope genes of these endogenous sequences are partially homologous to p15E provide potential candidates for the p15E-related inhibitors of chemotactic responses which have been identified from human cancer cells and fluids. Studies now under way in a number of laboratories should provide more definitive answers regarding the nature and source of these p15E-related inhibitors.(ABSTRACT TRUNCATED AT 400 WORDS)

Rejection of murine ovarian cancer following treatment with regional immunotherapy: correlations with a neutrophil-mediated activation of cytostatic macrophages

Rejection of the murine ovarian teratocarcinoma (MOT) in C3HeB/FeJ mice, following intraperitoneal (ip) treatment with Corynebacterium parvum (C. parvum), is abrogated by injections of silica. We, therefore, investigated whether C. parvum-elicited macrophages affect MOT targets in vitro. Tumor-cytostatic, but not cytolytic, macrophages were detected in normal and tumor-challenged mice treated with C. parvum. The dose responsiveness and kinetics of macrophage activation strongly correlated with tumor rejection. A pyridine extract of C. parvum, possessing greatly diminished tumor rejection properties, was significantly less effective in activating macrophages. Cytostatic macrophage activation and prevention of tumor outgrowth also followed treatment in C3H/HEJ mice, a strain with a known deficiency in cytolytic macrophage function. Peritoneal neutrophils, obtained 6 hr after treatment with C. parvum, were capable of activating cytostatic macrophages when reinjected ip into normal mice. These results indicate a critical role for tumor cytostatic macrophages in this immunotherapy model and suggest their activation is mediated by inflammatory neutrophils.

C. parvum treatment of transplanted rat tumours of spontaneous origin

C. parvum (Wellcome CN6134) has been examined for suppression of a range of transplanted rat tumours of spontaneous origin. With five tumours (three mammary carcinomas and two fibrosarcomas) growth of comparatively high cell inocula (with respect to the minimum for growth in control rats) was suppressed by admixture with the vaccine. Equivalent dry weights of Glaxo, Pasteur or Connaught BCGs were relatively ineffective. Intralesional injection of C. parvum into three three established tumours (two mammary carcinomas and one fibrosarcoma) retarded development of only one, the mmamary carcinoma Sp4. With three mammary carcinomas and one fibrosarcoma, active specific immune stimulation with vaccines of viable or irradiated cells admixed with C. parvum was again consistently effective only with carcinoma Sp4, and this tumour was also susceptible to intradermal but not intravenous treatment with C. parvum alone.

A survey of the effect of metals on the immune response

Evidence has been presented that the effect of metals on the immune response is highly variable: either enhancement or suppression may occur, depending on metal dose, route of inoculation, nature of antigenic stimulus, time of metal administration in relation to antigen, or the specific class of immunoglobulins produced. Very little is known of the mechanisms of metal-induced suppression or enhancement; mitogenicity of some metals may be involved in their stimulatory effects on immunity.An evaluation of available data shown no significant difference in the effect of carcinogenic and noncarcinogenic metals on immunity; the general effect of carcinogenic metals appears to be that of immunosuppression, but enhancement of immunity may also occur.Additional studies are needed to define immunological effects of carcinogenic and noncarcinogenic metals. Few experiments have analyzed the effects of these metals on cellular aspects of immunity, and, especially on those immunological reactions that play a role in tumor suppression or enhancement.

Effects of Corynebacterium parvum on murine myeloid leukaemia

The effects of C. parvum on RFM/UN myeloid leukaemia were studied. Mice inoculated with 7.0 mg but not 0.7 mg C. parvum i.p. survived significantly longer than untreated leukaemic mice (P less than 0.001). Administration of silica abrogated the effects of C. parvum, whilst polyvinyl pyridine-N-oxide prevented the inhibitory effects of silica. These studies demonstrate that a single large dose of C. parvum, either before or after leukaemic-cell passage, can significantly prolong the survival of RFM mice bearing myeloid leukaemia. The effects of silica and PVNO on C. parvum suggest a critical role for macrophages in C. parvum effects on myeloid leukaemia.

C. parvum immuntherapy of transplanted rat tumours

C.parvum (Wellcome CN 6134) has been tested for tumour suppression against a range of syngeneically transplanted rat tumours, both carcinogen-induced and of spontaneous origin. Subcutaneous growth was not prevented by distant subcutaneous or intravenous injection of the preparation, although growth rates were sometimes depressed or accelerated. In contrast, C. parvum injected in admixture with tumour cells consistently suppressed their growth and with highly immunogenic tumours induced systemic tumour immunity, C. parvum injected intravenously retarded development of pulmonary tumour deposits, and intrapleural injection suppressed growth of pleural tumours and malignant effusions. Host immunosuppression failed to abrogate the tumour-suppressive effect of locally applied C. parvum, but host macrophage depletion with silica totally abolished the response. These studies indicate that in the rat, tumour suppression is most consistently achieved by regional application of C. parvum, and that this response is more dependent upon local macrophage stimulation than generation of systemic immune responses.

Effects of Corynebacterium parvum on tumour metastases in mice

The effects of Corynebacterium parvum on the Lewis lung tumour and its metastases have been studied. Intravenous but not intraperitoneal or subcutaneous C. parvum reduced the growth of the primary tumour. Both intravenous and intraperitoneal C. parvum significantly reduced pulmonary metastases. When combined with excision of the primary tumour, C. parvum given not more than 2 days before excision caused only slight reduction of metastases, but when given intravenously or intraperitoneally 3–4 days before excision, metastases were significantly reduced and some mice were cured of tumour. Subcutaneous C. parvum had no effects on metastases.

Non-specific operation (amputation) increased tumour metastases, but C. parvum counteracted this.

Metastases were significantly increased by the administration of silica and cortisone acetate but were unaffected by trypan blue. The antimetastatic action of C. parvum was not significantly altered by these treatments. Thymectomy and irradiation did not affect tumour metastases or the antimetastatic action of C. parvum, whereas antilymphocyte serum depressed metastasis and abrogated the protective effects of C. parvum.

It appears that the inhibitory effects of C. parvum on tumour metastases are mediated through macrophages in concert with a subpopulation of T2 lymphocytes.

Immunological mechanisms in metastatic spread and the antimetastatic effects of C. parvum

The effects of the host's immune response on metastatic spread was investigated by observing the numbers of pulmonary metastases that developed from an s.c. implant of the Lewis lung carcinoma in C57BL mice in which different cell populations had been suppressed. Macrophage function was impaired by treatment with silica (Si), cortisone acetate (CA), or trypan blue (TB). T-cell function was depressed by adult thymectomy and sublethal irradiation, or by treatment with antilymphocyte serum (ALS). Metastasis was significantly increased and phagocytic activity decreased by Si and CA, but were unaffected by TB. Thymectomy and irradiation had no effect on metastases, whereas ALS when given before, but not after tumour growth, reduced their number. The antimetastatic action of the immunopotentiating agent C. parvum was investigated in these immunologically impaired mice. It was unaffected by Si, CA or TB. However, the inhibiting effect of these agents on phagocytic activity was overcome by treatment with C. parvum. Its antimetastatic action was unaffected in mice which had been thymectomized and irradiated, but could be abrogated by ALS. However, ALS was only able to prevent this activity if given before tumour growth; it was ineffective if given after tumour growth. This study showed that metastatic spread was inversely related to phagocytic activity. The antimetastatic effect of C. parvum appears to be mediated through macrophages in concert with a subpopulation of T lymphocytes, which were considered to be necessary in the sensitization arm of the response as opposed to the effector arm of this response.

Rubella virus and rheumatoid arthritis

A collection of synovial fibroblasts from 19 patients with rheumatoid arthritis (RA) and 12 patients with osteoarthrosis or other non-RA disease has been examined for rubella virus antigens by immunofluorescence and radioimmunoassay with negative results. Eluates of synovial membrane prepared under conditions likely to dissociate antigen-antibody complexes have shown no rubella antibody. A serological survey of RA patients and those with other forms of arthritis has shown no differences in the frequency or levels of rubella haemagglutination-inhibiting antibody. These results provide little support for various hypotheses that a persistent infection with rubella virus underlies or initiates the rheumatoid process.