Macrophage-neoplastic cell interactions: implications for neoplastic cell growth.

Subcutaneous transplantation of EL4 lymphoma cells within C57BL10 mice evoked an oedematous inflammatory response involving increased leukopoiesis within the bone marrow, a blood leukocytosis, an influx of leukocytes into the transplants and surrounding host connective tissues, and extensive remodelling of surrounding host connective tissues involving fibroplasia and angiogenesis. Dexamethasone not only significantly reduced the numbers of circulating blood leukocytes within C57BL10 mice bearing the subcutaneous EL4 lymphoma transplants, but also reduced the oedematous inflammatory response to the transplants. The decreased influx of inflammatory leukocytes into the site of EL4 lymphoma cell transplantation within the dexamethasone-treated mice, was accompanied by reduced growth of the transplants. Although the EL4 lymphoma cells produce factors with Colony Stimulating Factor activity and with chemotactic activity for cells of the monocyte-macrophage lineage, they do not appear to produce fibroblast growth factors directly but can induce (or stimulate) macrophages to generate fibroblast growth factors in vitro. While not directly inhibiting the growth of subcutaneous fibroblasts in vitro, dexamethasone does suppress the production and/or activity of fibroblast growth factors generated through macrophage-EL4 cell interactions in vitro. The inhibitory effects of dexamethasone on macrophage influx, fibroplasia and angiogenesis within the connective tissue surrounding the EL4 lymphoma transplants appear to be casually related events and would account for the inhibitory effect of dexamethasone on the growth of the lymphoma transplants.

The influence of FK-506 on the thymus: an immunophenotypic and structural analysis.

The influence of the powerful new immunosuppressant FK-506 on the thymus was investigated in Sprague-Dawley rats that were immunized with sheep erythrocytes and treated with FK-506 (1 mg/kg/day i.m.) for 7 days. Suppression of humoral immunity in drug-treated animals was accompanied by reductions in circulating lymphocytes bearing activation markers (interleukin-2 receptor beta-chain and OX40, activated CD4+ cells) and by striking thymic medullary atrophy. There were, however, no significant differences in thymic weights or in thymocyte numbers between experimental and control groups during the period of FK-506 administration. Reduction of the medullary compartment was visualized immunohistochemically, by decreases in major histocompatibility complex (MHC) class I- and MHC class II-positive cells and in CD37+ (mature medullary) thymocytes. Flow cytometric analysis of thymocytes showed that FK-506 induced increases in bright, Thy-1.1+ cells and in numbers of CD4+ and CD8+ thymocytes, whilst CD37+ cells were less numerous than in controls. Percentages of MHC class I- and MHC class II-positive cells varied little throughout the course of FK-506 administration. Evidence of selective damage to medullary epithelial cells, attributable to FK-506, was found at both the light and electron microscopic levels, whilst thymic macrophages in drug-treated rats displayed features of enhanced phagocytic activity, including ingestion of damaged epithelial cells. These FK-506-induced abnormalities were reversed within 14 days of drug withdrawal. These findings suggest that, like cyclosporin A, FK-506 reversibly disrupts the thymic microenvironment and may interfere with the function/maturation of T lymphocytes.

Tumour-induced suppression of delayed-type hypersensitivity in the mouse: independence of cyclophosphamide-sensitive suppressor cells.

Delayed-type hypersensitivity (DTH) responses to sheep red blood cells and ovalbumin were markedly reduced in mice receiving viable Landschütz ascites tumour cells at the time of immunization. Similar inhibitory effects were observed in control immunized animals when cell-free ascitic fluid or tumour bearer serum was administered together with antigen at the challenge site. Normal mouse serum exhibited much less pronounced inhibitory activity over the range of concentrations tested. High-dose cyclophosphamide (Cy) prior to immunization enhanced DTH responses to both antigens in normal mice. However, in animals also given tumour or soluble tumour-associated material, the immunosuppressive effect which had been observed in non-Cy-treated controls was preserved. It is concluded that the observed suppression of DTH is not dependent on Cy-sensitive T suppressor cells or on the presence of immunosuppressive factors during induction of the immune response.

Inhibition by the Landschütz ascites carcinoma of the granulomatous inflammatory response to C. parvum.

I.p. or i.v. administration of Corynebacterium parvum (CP) to MF1 mice induces a generalized inflammatory response, associated with marked hepatosplenomegaly and accompanied by a pronounced granulomatous response in the liver. Injection of the Landschütz ascites carcinoma (LAC) 24 h after CP substantially reduced the intensity of the inflammatory response, and decreased both the frequency and size of the hepatic granulomas, as revealed by morphometric analysis of histological sections. The difference in cellular composition of the granulomas between the experimental groups, as revealed by light microscopy, was further emphasized and characterized by ultrastructural studies. These revealed the predominance of macrophages within the granulomas in tumour-bearing mice, in contrast to the predominance of epithelioid cells in the lesions which developed in mice given CP alone. Our experimental findings show that the inhibitory effect of the growing LAC on granuloma formation in response to CP cannot be ascribed to (a) sequestration of the microorganism within the growing tumour, (b) a nonspecific inflammatory stimulus, (c) diversion and seqestration of mononuclear phagocytes in the growing tumour or (d) the presence of lactate dehydrogenase-elevating virus in either the host or tumour cells. The inhibition of liver granuloma formation is consistent with an effect mediated by soluble, heat-stable tumour-associated factor(s).

Effects of the Landschütz ascites carcinoma and ascitic fluid on macrophage activity in C. parvum-injected mice.

I.p. administration of 1.4 mg Corynebacterium parvum (C. parvum) 24 h before inoculation of Landschütz ascites carcinoma (LAC) cells significantly impaired growth of the tumour in MF1 mice. The injection of tumour cells caused a transient inhibition of the activity of the mononuclear phagocyte system (MPS) in both normal and C. parvum-treated hosts, as evidenced by impaired clearance of colloidal carbon from the bloodstream and reduction in hepatic phagocytosis of 51Cr-labelled sheep erythrocytes. Depression in Kupffer-cell activity was associated with a shift in particle distribution towards the spleen. The pronounced hepatosplenomegaly in response to C. parvum was significantly less in animals which also received tumour cells. Histological examination of liver and spleen revealed evidence of depressed MPS activity. Granuloma production in the liver in response to C. parvum was inhibited in tumour-bearing mice, and macrophage proliferation within the spleen was also reduced. Ascitic fluid showed similar inhibitory effects to those of tumour-cell suspensions, suggesting production by LAC of a heat-stable macrophage-inhibitory factor.

An ultrastructural study of peritoneal mononuclear phagocytes from Corynebacterium parvum-injected mice.

Peritoneal mononuclear phagocytes harvested from mice 24 h after i.p. injection of C. parvum displayed hypertrophy of the Golgi and smooth endoplasmic reticulum complex with attendant increase in lysosome production. The ingested bacilli were identified within phagolysosomes, within which large myelin figures accumulated. In addition to heterophagic vacuoles, autophagosomes and lipid droplets were observed. These latter two inclusions may reflect a direct or indirect cytopathic effect of C. parvum on the phagocytes.

An ultrastructural study of peritoneal mononuclear phagocytes from iota carrageenan injected mice.

Mononuclear phagocytes harvested from peritoneal cavities of mice injected intraperitoneally 24 h previously with iota carrageenan were invariably vacuolated or lysed. The incidence of lysed cells was approximately 25%. Carrageenan could be identified as fibrillar material within phagolysosomes of varying size, and retention of the fibrillar structure of this material, even within lysed cells, suggests that iota carrageenan is relatively resistant to biochemical degradation and hence persists within the phagolysosomes. The limiting membranes of many of the larger vacuoles were frequently ruptured, probably indicating osmotic stress on these membranes as the phagolysosomes swell.

Endocytosis of the antiprotease aprotinin by Landschütz ascites carcinoma cells and its effects in vitro and in vivo.

Aprotinin was bound and endocytosed by Landschütz ascites carcinoma (LAC) cells in vitro. Addition of the antiprotease to cultures of these cells led to a dose-dependent growth-inhibitory and cytotoxic effect. In mice inoculated with LAC cells and treated with aprotinin there was a transient reduction in both the number and concentration of recovered ascites cells during the early phase of tumour growth. This was accompanied by a temporary increase in the proportion of peritoneal phagocytes (mononuclear phagocytes and polymorphonuclear leucocytes) relative to carcinoma cells. However, the number and concentration of ascites cells eventually achieved was comparable in saline and aprotinin-treated animals.

Effects of the antiprotease Trasylol on peripheral blood leucocytes.

Binding of the antiprotease Trasylol to human peripheral blood lymphocytes and polymorphonuclear leucocytes (PMNs) was demonstrated at the ultrastructural level using an indirect immunoperoxidase technique. This also revealed endocytosis of membrane bound Trasylol by PMNs. Trasylol inhibited PHA- and ConA-induced lymphocyte stimulation, and was cytotoxic to unstimulated cells.

A new method for the simultaneous assay of rosette-forming and antibody-secreting cells, utilising immune adhesion reactions in monolayer.

Mixtures of sheep erythrocytes and immune spleen cells from mice were incubated in shallow slide chambers coated with erythrocyte ghosts or anti-mouse Ig, with poly L-lysine as a coupling agent. Antigen-binding cells and erythrocytes surrounding antibody-releasing lymphocytes became bound to the reactive surfaces by immunocytoagglutination and could be readily observed on inversion of the chambers. The sensitivity of the method compares with those currently in use for quantification of antibody-releasing cells, and resolution of rosettes is markedly superior to that obtainable in other assay systems. The advantages and limitations of the method are discussed.

Aprotinin and growth of Walker 256 carcinosarcoma in the rat.

Growth of the Walker 256 carcinosarcoma implanted within various sites in Spraque-Dawley rats was investigated in animals receiving twice daily i.p. injections of the antiprotease aprotinin. Although administration of aprotinin partially attenuated the growth and lethality of i.p. tumour, no effect of aprotinin was found on intramuscular tumour development. Furthermore, we were unable to demonstrate unequivocal growth inhibition by aprotinin of lung tumour colonies from i.v. injection of tumour cells. Histological examination of intramuscular and pulmonary tumours revealed little evidence of host cellular immune response in either saline- or aprotinin-treated rats.

Pregnancy specific beta1-glycoprotein--a product of the syncytiotrophoblast.

Pregnancy specific beta1-glycoprotein (PSbetaG) has been identified in vitro in trophoblast cultures and in vivo, using transmission electron microscopy, in the syncytiotrophoblast, PSbetaG may, like other pregnancy proteins, have immunosuppressive properties.