Recognition and destruction of neoplastic cells by activated macrophages: discrimination of altered self

Modulation of macrophage function by transforming growth factor beta, interleukin-4, and interleukin-10

The findings reviewed above leave no doubt as to the complexity of actions of TGF-beta, IL-4, and IL-10 on monocytes/macrophages. Along with MDF, whose actions were recently reviewed elsewhere, TGF-beta, IL-4, and IL-10 are the only presently known, purified cytokines that have been shown to have strong macrophage-deactivating effects. However, none of them can be categorized as purely macrophage deactivating since they also exert macrophage-activating effects. In vitro, their effects, both in terms of extent and direction (activating vs. deactivating), are strongly influenced by the stimulation conditions (e.g., triggering signal, cytokine concentration, timing of cytokine addition), the species (mouse vs. human), the source (blood vs. peritoneal, alveolar, colostral) and the state of differentiation/activation of the macrophage (e.g., resting vs. inflammatory). In addition, TGF-beta, as well as IL-4 and IL-10, up- and/or downregulates the function of several cell types other than macrophages, which further hampers our ability to predict, on the basis of in vitro experiments with macrophages, possible effects during an immune response in vivo. Despite this complexity, the highly reductive approach of in vitro studies has revealed important differences in the ability of TGF-beta, IL-4, and IL-10 to modulate the phenotype of monocytes/macrophages. The disparities have been most striking with regard to the secretory function of monocytes/macrophages (see Table 2). First, TGF-beta, IL-4, and IL-10 have a different spectrum of activity. Thus, TGF-beta, but not IL-4 or IL-10, can induce resting human monocytes to produce TNF, IL-1, and IL-6. Second, they affect monokine and RNI and ROI production to a different extent. For example, IL-10 is an approximately 25-fold more potent suppressor of LPS-induced TNF production by mouse macrophages than is TGF-beta. Third, they differ in their ability to overcome additional activating stimuli, so that in the presence of LPS, IL-4, but not TGF-beta or IL-10 suppresses IFN gamma-induced RNI release. Fourth, their macrophage-deactivating effects require different stimulation conditions. Thus, IL-4, but not TGF-beta, interferes with RNI release strongly only after preincubation of the macrophages. Finally, these agents deactivate macrophages by distinct mechanisms. For example, IL-10 causes massive downregulation of TNF mRNA, whereas TGF-beta suppresses TNF release on a translational level. It will be a challenge to define clinical applications for these potent macrophage modulators on the basis of their different spectrum of activities. For TGF-beta and IL-4 such studies have already been initiated.

Uptake of phosphatidylserine liposomes by rat Peyer's patches following intraluminal administration

Uptake of the nonabsorbable marker 6-carboxyfluorescein was investigated both free and encapsulated in liposomes as a function of their surface charge and hydrodynamic diameter in rat Peyer's patch and nonpatch tissue. Significant uptake of the marker occurred only when encapsulated in liposomes consisting of at least 25 mol% phosphatidylserine and was highest in Peyer's patches. 6-Carboxyfluorescein encapsulated in liposomes equal to or greater than 374 nm was preferentially taken up by Peyer's patches. There was a trend to higher uptake in lower intestinal segments. These findings were supported by fluorescence microscopic observations. Uptake by Peyer's patches was specific for negatively charged liposomes as judged from competition studies.

Production of reactive nitrogen intermediates by bone marrow-derived macrophages on treatment with cisplatin in vitro

L929 culture medium (a source of macrophage colony stimulating factor (M-CSF) or recombinant granulocyte-macrophage colony stimulating factor (rGM-CSF)-derived bone marrow macrophages treated with cisplatin or lipopolysaccharide (LPS) (10 micrograms/ml) were effective in the production of L-arginine-dependent reactive nitrogen intermediates (RNI) and generation of tumouricidal activity. The abilities of RNI secretion and related tumouricidal activity against P815 mastocytoma cells were compared. These parameters were found to be closely correlated in various experiments. RNI secretion and generation of bone marrow macrophage-mediated tumouricidal activity were significantly inhibited by L-N-monomethyl arginine (L-NMMA), a specific inhibitor of the L-arginine pathway, but L-NMMA did not inhibit macrophage-mediated killing of tumour necrosis factor (TNF)-sensitive Wehi cells, suggesting that activated macrophages exhibit at least two cytolytic mechanisms, one by L-arginine-dependent nitric oxide pathway and another by TNF-mediated killing. The present findings suggest that the mechanism of tumour cell killing by activated macrophages may differ, depending on the tumour cell type, and reactive nitrogen intermediates play a major role in cisplatin-mediated activation of bone marrow-derived macrophages.

Interleukin-3 induces antimicrobial activity against Leishmania amazonensis and Trypanosoma cruzi and tumoricidal activity in human peripheral blood-derived macrophages

The ability of interleukin-3 (IL-3) to induce antimicrobial and tumoricidal activity was evaluated. Macrophages infected with two intracellular protozoa, Leishmania amazonensis or Trypanosoma cruzi, were treated with cytokines. IL-3 induced a dose-dependent enhancement of microbistasis against leishmanias, and the activity of IL-3 (100 ng/ml) was comparable to that of gamma interferon (IFN-gamma) (1,000 U/ml). In addition, IL-3 in combination with either granulocyte-macrophage colony-stimulating factor (GM-CSF) or macrophage CSF (M-CSF) or with IFN-gamma reduced infection and lowered the required dose. IL-3 similarly activated macrophages to inhibit intracellular replication of T. cruzi. Furthermore, IL-3 induced antibody-independent tumoricidal activity against melanoma cells that was dose dependent and comparable to that of lipopolysaccharide and GM-CSF. The mechanisms by which IL-3 induced antimicrobial activity may involve at least the augmentation of oxidative capacity. IL-3, at concentrations of 0.5 ng/ml or greater, led to a significantly increased oxidative burst which paralleled the inhibition of protozoan replication. The enhancement of oxidative capacity by IL-3 (5 ng/ml or higher) was comparable to that of IFN-gamma. The induction of tumoricidal activity was associated with the production of tumor necrosis factor alpha (TNF-alpha), which in this system may feed back to enhance the macrophage inhibition of leishmanias, as demonstrated by neutralization of IL-3 activation by anti-TNF-alpha antibody. Thus, peripheral blood macrophages remain responsive to IL-3, as demonstrated by enhanced antimicrobial and tumoricidal activity. IL-3 may have potential clinical applications because of these properties and its effect on myelopoiesis.

Effect of interferon-gamma priming on the activation of murine peritoneal macrophages to tumouricidal state by cisplatin, IL-1, and tumour necrosis factor (TNF): production of IL-1 and TNF

The effect of interferon-gamma (IFN-gamma) priming of murine peritoneal macrophages on the activation to tumouricidal state by cisplatin, lipopolysaccharide (LPS)-IL-1 and TNF was investigated. Cisplatin-, LPS-, IL-1- or TNF-treated IFN-gamma-primed macrophages showed significantly enhanced tumouricidal activity and binding to tumour cells, compared with unprimed treated or untreated macrophages. Macrophages treated with cisplatin, LPS, IL-1 and TNF produced released and membrane-associated IL-1 and TNF activity which was significantly enhanced after priming with IFN-gamma. These observations suggest the use of IFN-gamma along with these biological response modifiers in designing immunotherapeutic protocols for treatment of malignancy.

In vitro study of contact-mediated killing of Candida albicans hyphae by activated murine peritoneal macrophages in a serum-free medium

Activated peritoneal macrophages obtained from Listeria-immune mice were demonstrated to kill nonphagocytosable Candida albicans hyphae by contact-mediated mechanisms in a serum-free synthetic medium. The actual killing of hyphae was confirmed by a microculture technique utilizing the dimorphic nature of the fungus. The most efficient candidacidal activity was demonstrated by the macrophages obtained from mice first immunized with live Listeria monocytogenes and then elicited with heat-killed L. monocytogenes cells. Resident macrophages from control mice showed only low candidacidal activity against C. albicans hyphae and yeast cells. Direct physical contact appeared to be required for macrophages to efficiently kill oversized C. albicans hyphae. Efficient in vitro killing of hyphae also required relatively high effector/target cell ratios (50 or higher). The contact-mediated candidacidal activity of activated macrophages was not significantly abrogated by oxygen-radical scavengers, suggesting the involvement of oxygen-independent mechanisms. These results suggest that the enhanced nonspecific immunity to candidiasis seen in Listeria-immune hosts can be attributed, at least in part, to activated fungicidal macrophages. The ability of macrophages to detect and destroy both yeast and hyphal C. albicans cells is clearly an important element of the host defense against candidiasis.

Squamous cell carcinoma: infiltrating monocyte/macrophage subpopulations express functional mature phenotype

Biopsies from 26 patients with advanced stage squamous cell carcinoma of the head and neck were investigated to determine the intensity of the inflammatory cellular infiltrate and the expression of leucocyte antigens. Mononuclear cell infiltration varied considerably between the individual patients and also within the tumour. Tumour-infiltrating cells consisted mainly of T lymphocytes and monocytes (Mo)/macrophages (M phi). Staining procedure with monoclonal antibodies (moabs) against Mo/M phi revealed different clusters of antigen expression: (1) moabs 27E10 and a-CD35 detected a subgroup of Mo/M phi with particular staining of perivasal Mo; (2) moab a-CD1 stained preferentially cells in tumour cell clusters; (3) moabs that reacted with cells of either typical M phi or dendritic morphology throughout the tumour-tissue: a-Fc gamma receptor I-III, a-class II antigens, a-CD4, Rm3/1, a-CD36 and 25F9. Thus, the majority of tumour-infiltrating mononuclear phagocytes were found to possess a rather mature phenotype. The number of Mo/M phi with mature phenotype within the tumours correlated with T lymphocyte infiltration in the tissue.

Macrophages and cancer

The uncontrolled growth of metastases resistant to conventional therapeutic modalities is a major cause of death from cancer. Data from our laboratory and others indicate that metastases arise from the nonrandom spread of specialized malignant cells that preexist within a primary neoplasm. These metastases can be clonal in their origin, and different metastases can originate from different progenitor cells. In addition, metastatic cells can exhibit an increased rate of spontaneous mutation compared with benign nonmetastatic cells. These data provide an explanation for the clinical observation that multiple metastases can exhibit different sensitivities to the same therapeutic modalities. These findings suggest that the successful therapy of disseminated metastases will have to circumvent the problems of neoplastic heterogeneity and the development of resistance. Appropriately activated macrophages can fulfill these demanding criteria. Macrophages can be activated to become tumoricidal by interaction with phospholipid vesicles (liposomes) containing immunomodulators. Tumoricidal macrophages can recognize and destroy neoplastic cells in vitro and in vivo, leaving nonneoplastic cells uninjured. Although the exact mechanism(s) by which macrophages discriminate between tumorigenic and normal cells is unknown, it is independent of tumor cell characteristics such as immunogenicity, metastatic potential, and sensitivity to cytotoxic drugs. Moreover, macrophage destruction of tumor cells apparently is not associated with the development of tumor cell resistance. Macrophages are found in association with malignant tumors in a definable pattern, suggesting that the most direct way to achieve macrophage-mediated tumor regression is in situ macrophage activation. Intravenously administered liposomes are cleared from the circulation by phagocytic cells, including macrophages, so when liposomes containing immunomodulators are endocytosed, cytotoxic macrophages are generated in situ. The administration of such liposomes in certain protocols has been shown to bring about eradication of cancer metastases. Macrophage destruction of metastases in vivo is significant, provided that the total tumor burden at the start of treatment is minimal. For this reason, we have been investigating various methods to achieve maximal cytoreduction in metastases by modalities such as chemotherapy or radiotherapy prior to macrophage-directed therapy. It is important to note that even the destruction of 99.9% of cells in a metastasis measuring 1 cm2 would leave 10(6) cells to proliferate and kill the host. The ability of tumoricidal macrophages to distinguish neoplastic from bystander nonneoplastic cells presents an attractive possibility for treatment of the few tumor cells which escape destruction by conventional treatments. Macrophage-directed therapy has been studied in several human protocols, yielding important biological information about the use of liposome-encapsulated macrophage activators in cancer patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Diagnosis and recommended management of esophageal perforation and rupture

Over the past 47 years (1937 to 1984), a total of 127 patients with esophageal perforation or rupture were evaluated at Duke Medical Center or the Durham Veterans Administration Medical Center. In 13 patients, the diagnosis was established at the time of autopsy and in the remaining 114, the diagnosis was established clinically. The etiology, radiological findings, underlying esophageal disease, time interval between onset of symptoms and therapy, and eventual outcome were evaluated. Patients with anastomotic leaks and those in whom carcinoma resulted in perforation or fistula were excluded. Iatrogenic causes were responsible for 55% of perforations, followed by spontaneous rupture in 15%, foreign body perforation in 14%, and traumatic perforation in 10%. Of the 127 patients, 114 underwent treatment involving primary closure (43%), drainage alone (28%), resection (9%), or nonoperative therapy (20%). The overall mortality among these 114 patients was 21%. Fourteen patients sustained a major complication requiring additional operative intervention. The overall mortality among patients requiring reoperation was 57%. Survival was significantly influenced by a delay in treatment of greater than 24 hours. With the exception of nonoperative therapy, survival was improved for all forms of treatment instituted within 24 hours. Primary closure within 24 hours resulted in the most favorable outcome (92% survival). In addition to early treatment, other factors associated with a favorable outcome included traumatic perforation (100% survival), foreign-body perforations (94% survival), and iatrogenic causes (80% survival). Spontaneous rupture resulted in the lowest survival (37%). The incidence of esophageal perforation has increased dramatically since 1967.(ABSTRACT TRUNCATED AT 250 WORDS)