Functional and biochemical parameters of activation related to macrophage cytostatic effects on tumor cells

"Activated" monocytes in gastric cancer patients. II. Suppressor and cytostatic activity in vitro

The spontaneous nitro-blue tetrazolium (NBT) reduction of monocytes from patients with gastric cancer was assessed and compared with an in vitro monocyte-mediated cytostasis of tumor cell lines and their suppressor activity. The increased NBT reduction correlated with the ability of monocytes to inhibit mitogen-induced normal lymphocyte response and cytostatic activity against L-1210 murine lymphoma cell line. These observations suggest that "activated" monocytes of some cancer patients may play the role of suppressor cells and exert an anti-tumor effect in vitro.

Regulation of glycoprotein biosynthesis by formation of specific glycosyltransferase complexes

Eukaryotic surfaces simultaneously express a complex array of protein-linked oligosaccharides and, during differentiation and on neoplastic transformation, these arrays change. The oligosaccharides linked to asparagine residues of proteins are a complex family of structures that are derived from a common precursor oligosaccharide by a network of competing biosynthetic pathways. The glycosylation reactions that make up these biosynthetic pathways often share common intermediates, requiring the competition between rival glycosyltransferases to be regulated at the supramolecular level. Investigation of two sequential glycosyltransferases that together add N-acetyllactosamine to glycoproteins has revealed their ability to form specific complexes. The functional consequences of complex formation were assessed by investigating the coupled reaction carried out by these sequential enzymes. The membrane enzymes are readily adsorbed by preformed liposomes, and their ability to interact after liposome adsorption has allowed direct investigation of the action carried out by these sequential enzymes when they are coadsorbed to the same liposome or adsorbed to separate liposomes shows the preferential use of endogenously generated intermediate over exogenously added glycoproteins. This facilitated passage of the intermediate glycosylated glycoprotein within the complex results in a tight coupling of the sequential enzymes. The formation of such complexes by sequential glycosyltransferases is proposed as a mechanism for controlling the competition between potentially rival glycosylation sequences during glycoprotein synthesis. The formation of different specific complexes under different conditions provides a flexible mechanism for regulating the synthesis of cell surface glycoproteins during development.

Corynebacterium parvum treatment of P388 tumor-bearing mice. I. Lysosomal enzyme levels in adherent peritoneal cells and peritoneal lavage fluid

BDF1 mice treated with Corynebacterium parvum (C. parvum) 2 days before an implant of 106 P388 leukemic cells had up to an 110% increase in survival time above control; Bacillus Calmette-Guérin (BCG) treatment was ineffective. Acid phosphatase and beta-glucuronidase were measured in adherent peritoneal lavage cells and beta-glucuronidase in peritoneal lavage fluid form mice treated with C. parvum or BCG 2 days before the implant of P388 cells. In the presence of the tumor, adherent peritoneal cells from C. parvum-treated animals had a 250-300% increased specific lysosomal enzyme activity above control values (cells form animals receiving tumor implant alone). Peak enzyme activity which occurred on day 3 was not present in adherent cells from BCG-treated tumor-bearing animals or the control animals. The beta-glucuronidase activity in peritoneal lavage fluid was elevated by the tumor cells, BCG, or C. parvum. Peak levels occurred on day 5 regardless of the treatment with an additive effect present on day 5 in animals receiving the combination of tumor with C. parvum. The evidence indicated the development of a different pattern of enhanced lysosomal enzyme activity if the immunopotentiator protected against the P388 tumor vs one that did not. Protection was associated with an increase in lysosomal enzyme activity in adherent cells with no increase in lavage fluid in the presence of tumor cells. Changes in cellular enzyme activity may prove to be diagnostic for antitumor activity by an immunostimulant.

Fungicidal activity of rabbit alveolar and peritoneal macrophages against Candida albicans

We tested the ability of rabbit macrophages to kill Candida albicans in vitro. Resident (unstimulated) alveolar macrophages killed 28.1 +/- 1.9% of ingested organisms in 4 h, whereas resident peritoneal macrophages killed only 15.2 +/- 1.3% (mean +/- standard error of the mean, P < 0.01). Peritoneal macrophages obtained from rabbits treated 3 weeks earlier with complete Freund adjuvant showed enhanced candidacidal activity relative to normally resident peritoneal cells (28.2 +/- 3.1%, P < 0.01). Candidacidal activity by alveolar macrophages recovered from such treated animals was slightly enhanced relative to untreated alveolar macrophages (32.9 +/- 2.3%). Candidacidal activity by peritoneal and alveolar macrophages was not decreased by several agents (cyanide, azide, sulfadiazine, and phenylbutazone) that inhibit the ability of human blood monocytes to kill C. albicans. In contrast, candidacidal activity by alveolar macrophages was greatly diminished by iodoacetate, an ineffective inhibitor of this function in human monocytes. We conclude that rabbit macrophages kill C. albicans by a fungicidal mechanism distinct from the peroxidase-H2O2 mechanism of human granulocytes and monocytes, and that the fungicidal properties of peritoneal and alveolar macrophage populations are enhanced after nonspecific stimulation with complete Freund adjuvant.

Dose-dependent macrophage stimulation by Corynebacterium parvum

Corynebacterium parvum (C. parvum) administered at a dose of either 0.1, 1 or 10 mg/kg intraperitoneally (ip) to BDF1 mice was evaluated for its influence on peritoneal exudate cell differentials, numbers, respiration, phagocytic activity and capacity and intracellular microbicidal activity. The ip administration of 1 mg/kg of C. parvum resulted in a 2-3 fold increase in the yield of peritoneal exudate cells 1-5 days after injection; 0.1 mg/kg was ineffective, while 10 mg/kg of C. parvum manifested an increased cell yield on days 1 and 5 following injection. No alterations in cell differentials were noted at any dose level. A trend toward a dose-related alteration in the respiratory burst, phagocytic activity and capacity was demonstrated. The most dramatic alteration observed was a profound increase in intracellular microbicidal activity in macrophages obtained from mice administered 1 mg/kg of C. parvum. The higher dose of C. parvum was suppressive. It was concluded that a relationship between macrophage microbicidal activity and tumor cell killing exists because the 1 mg/kg, which elicited maximal macrophage microbicidal activity, also induced the greatest increase in protection against two unrelated tumor models as previously reported.

Normal human monocytes inhibit tumor cell growth in vitro

Normal human monocytes were evaluated in an in vitro assay of growth inhibition of tumor cells. Monocytes were isolated from the blood of 6 normal subjects by Ficoll-Hypaque separation and adherence to plastic microtest wells. Cervical carcinoma cells (HeLa) were added to the microwells to result in a ratio of 50 monocytes to one HeLa cell. Cultures were then incubated for 6 to 46 hr. Growth inhibition was evaluated by measuring the uptake of 3H-thymidine over a 4-hr pulse period after 2, 18, or 42 hr of monocyte-HeLa interaction. Inhibition of HeLa growth by monocytes was 23.8% +/- 8.6% over 6 hr, 22.0% +/- 8.9% over 22 hr. and 68.3% +/- 7.5% over 46 hr. Growth inhibition of HeLa cells was confirmed by direct enumeration of HeLa cells at the end of coincubation. Attachment of monocytes to the HeLa cells was confirmed by light and scanning electron micrographs. Granulocytes, lymphocytes, and other cell lines did not comparably inhibit HeLa growth and media replenishment did not ablate the effect. These data demonstrate that normal human monocytes can inhibit the growth of a malignant cell line in vitro in the absence of overt activation procedures.

Activation and cytotoxic activity of macrophages: a short review

Interaction of sensitized T-lymphocytes with specific antigen, as well as several other nonimmunological stimuli, will induce the appearance of new properties in macrophages collectively referred to as "activation". The importance of macrophage activation in various physiological processes is only just beginning to be understood. A growing body of evidence strongly suggests that activated macrophages may play a dual role: firstly in protecting the host against certain interacellular pathogens, and secondly in modulating cell proliferation and adversely affecting cells with abnormal growth properties. It is expected that the ability of activated macrophages to discriminate between normal and tumor cells will receive increasing attention. If confirmed, this property may be of major importance with regard to immunotherapy of tumors.