Macrophage activation: dissociation of cytotoxic activity from Ia-A antigen expression

Human MCF activates monocytes to produce IL-1 but not TNF or CSF-1

Monocyte cytotoxicity inducing factor (MCF) is a novel cytokine which was originally characterized by its ability to induce monocyte cytotoxicity against tumor targets. The present studies were undertaken to define the mechanisms of cytotoxicity. Since the cytotoxic state may be mediated, in part, by the secretion of monokines, MCF's effect on IL-1, TNF and CSF-1 were measured. MCF caused human peripheral blood monocytes to secrete large amounts of IL-1 but not TNF. In contrast monocytes produce CSF-1 in culture and this production was not enhanced by MCF. IL-1 neither appeared to directly lyse the target K562 nor was able to activate macrophages for cytotoxicity. However, IL-1 may be necessary for lysis of K562 by activated macrophages through its cytostatic effect on K562. MCF increased monocyte surface expression of DR-beta (when studied by fluorescent microfluorometry) and messenger RNA for DR-beta after 24 h in culture. These functional studies indicate that MCF is a cytokine with a distinct spectrum of biologic activities whose functions may be mediated by synthesis and secretion of IL-1.

Inhibition of Ehrlichia risticii infection in murine peritoneal macrophages by gamma interferon, a calcium ionophore, and concanavalin A

Ehrlichia risticii incubated with mouse peritoneal macrophages elicited with thioglycolate broth survived and replicated, thereby allowing examination of the effects of several immunopotentiating agents. Treatment of the macrophages with recombinant murine gamma interferon (rMuIFN-gamma) in vitro at 1 day before or 3 h after infection made the macrophages resistant to infection with E. risticii, and macrophages treated with rMuIFN-gamma at 1 to 3 days after infection developed the capacity to eradicate intracellular E. risticii. Similar effects were seen with macrophages treated with the Ca2+ ionophore A23187 before or after E. risticii infection in vitro. Concanavalin A treatment before or 3 h after infection caused the macrophages to become resistant to infection with E. risticii but could confer neither ehrlichiacidal nor ehrlichiastic activity to them once infection had been established for more than 1 day. Bacterial products such as lipopolysaccharide and muramyl dipeptide were less or not at all effective, respectively, in conferring antiehrlichial activity to macrophages. Finally, protein kinase C activator, phorbol myristate acetate, and recombinant tumor necrosis factor did not induce any antiehrlichial activity in macrophages when the macrophages were treated either before or after infection.

Macrophage cell lines P388D1 and IC-21 stimulated with gamma interferon fail to inhibit the intracellular growth of Histoplasma capsulatum

Histoplasma capsulatum, a facultative intracellular parasite of macrophages, grows within mononuclear cells of the P388D1 and IC-21 cell lines with a generation time comparable to that with which it grows in normal resident peritoneal macrophages (10 +/- 2 h). Recombinant murine gamma interferon (rMuIFN-gamma) activates P388D1 cells to express la antigens but not to inhibit the intracellular growth of H. capsulatum, alone or in combination with lipopolysaccharide. IC-21 cells also could not be activated to fungistasis with rMuIFN-gamma. Explanted resident peritoneal macrophages of the C57BL/6 (from which the IC-21 cell line derives), C3H/HeJ, DBA/2 (from which the P388D1 cell line derives), A/J, and SJL/J strains of mice were all stimulated by rMuIFN-gamma to inhibit the fungus.

Immunophenotype of pulmonary cellular infiltrates in sheep with visceral caseous lymphadenitis

Pulmonary lesions associated with Corynebacterium ovis were analyzed with an indirect immunoperoxidase staining technique using monoclonal antibodies. The predominant cells in abscess walls and surrounding lung parenchyma were large macrophages which expressed major histocompatibility complex (MHC) class II molecules on their surfaces. T lymphocytes were prominent in the same sites in the naturally occurring lesions, and SBU-T4-positive ("helper/inducer") cells were the major subset of lymphocytes (mean T4/T8 ratio = 3.5). B lymphocytes and granulocytes comprised minor populations of infiltrating cells. These results implicate activated macrophages and MHC class II-restricted T lymphocytes in the pathogenesis of established C. ovis infections in sheep.

Modulation of major histocompatibility complex (MHC) expression by interferons and microbial agents. Independent regulation of MHC class II expression and induction of tumoricidal activity in bone marrow-derived mononuclear phagocytes

In a pure population of rat bone marrow-derived mononuclear phagocytes (BMM phi), the expression of major histocompatibility complex (MHC) molecules and ability to manifest tumoricidal activity were simultaneously studied. Resting BMM phi, which express low levels of MHC class II molecules and do not manifest tumoricidal activity, become strongly MHC class II-positive, and evolve tumoricidal activity within 24 h when incubated with macrophage-activating lymphokines (MAF) or gamma interferon (IFN-gamma). In contrast, BMM phi which were interacted for 24 h with heat-killed microbial agents (Corynebacterium parvum, Listeria) evolve tumoricidal activity without parallel enhancement of MHC class II expression. IFN-alpha,beta neither induced tumoricidal activity nor enhanced MHC class II expression. Further experiments have shown that (a) the kinetics of MAF- and/or IFN-gamma-induced amplification of MHC class II expression and of tumoricidal activity are different; (b) enhancement of MHC class II expression by rIFN-gamma is not invariably paralleled by induction of tumoricidal activity; and (c) inhibitors of macrophage tumoricidal activity differ in their ability to affect MHC class II expression. It is concluded from these findings that in a population of pure BMM phi, i.e. in the complete absence of lymphocytes, the expression of MHC molecules and induction of tumoricidal activity are independently regulated phenomena; in particular, the enhanced expression of MHC class II molecules is not a prerequisite for induction and/or manifestation of tumoricidal activity by mononuclear phagocytes.

Simultaneous expression of Ia and cytocidal activity by macrophages, and the consequences for antigen presentation

We have investigated whether the interrelationship of Ia expression and cytotoxicity by macrophages, as the two functions if expressed at the same time, might be counterproductive for T-cell development and function. We report that, under some circumstances, there is a clear dissociation of the two activities, as was demonstrated for both in vitro and in vivo conditions. However, the two functions could also be superimposed. Dissociation or superimposition was determined by (i) the nature of the inducing stimulus, and (ii) by the time-span between stimulation and evaluation. It was found that Ia and tumour killing were mainly expressed by the same macrophage population and, as a result, cytolytic activity, when associated with Ia expression, can be directed against T-cell hybridomas in an antigen-specific manner. The physiological relevance of the dissociation or superimposition of Ia expression and tumour killing by macrophages is discussed.

Antigens associated with various cytotoxic activities of murine peripheral macrophages

BCG- or glucan-elicited murine peripheral macrophages released a cytotoxin in the presence of loach egg lectin, whereas proteose peptone-, glycogen-, or thioglycollate-elicited or resident macrophages did not. The macrophages that released cytotoxin coincided with those that showed lectin-dependent macrophage-mediated cytolysis (LDMC) in response to loach egg lectin. The cytotoxin released by BCG-elicited macrophages in response to loach egg lectin had a molecular weight of 55 K daltons. The macrophages that released cytotoxin and other cytotoxic macrophages such as those that showed LDMC- and antibody-dependent macrophage-mediated cytolysis (ADMC) were examined by using several antibodies to surface antigens of macrophages. The results showed that murine peripheral macrophages could be divided into three types. Resident macrophages (Type I) which had common macrophage antigens (Mac-1 and B12) showed only LDMC in response to wheat germ agglutinin. Some elicited macrophages (Type II) were asialo GM1-positive and showed both ADMC and LDMC in response to wheat germ agglutinin. Activated macrophages (Type III) showed LDMC in response to loach egg lectin and cytotoxin-release, but had no antigen detectable with monoclonal anti-macrophage antibody (C14). These three types of macrophages were clearly distinguished diagrammatically by their roof-shaped, rocket-shaped and irregular-shaped profiles of activities and antigens. These data suggest that several selected surface antigens of macrophages are associated with distinct cytotoxic stages of peripheral macrophages.

Surface antigen expression by bovine alveolar macrophages: functional correlation and influence of interferons in vivo and in vitro

Alveolar macrophages (AM) procured by bronchoalveolar lavage of healthy calves were tested for the expression of two antigens defined by monoclonal antibodies. One of these, H34A, detects a MHC type II (Ia)-antigen; the other, B18A, a heterodimer of unknown function. No single AM-activity could be ascribed solely to the subpopulations defined by the presence or absence of these two surface antigens. The expression of both antigens could be modulated by in vitro treatment of the AM with recombinant E. coli-derived bovine interferon-gamma (rBoIFN-gamma), but not by interferon-alpha 1 (rBoIFN-alpha 1). Enhanced Ia-expression was detectable within 3 h of exposure to rBoIFN-gamma and reached a maximum by 24-48 h. Expression of the Ia-antigen required continual presence of bioactive IFN. However, cells that reverted from the Ia+ to the Ia- state did not become refractory to reinduction, and induction was possible even after several days (at least 96 h) in culture, despite the in vitro maturation and modulation of the AM that occurred. Treatment of calves with rBoIFN-gamma also resulted in increased numbers of Ia(H34A)+ cells, but in a decline of B18A+ cells. In contrast to the in vitro findings, rBoIFN-alpha 1 appeared to have some modulatory effect in vivo. The latter effect may be indirect rather than direct as for rBoIFN-gamma. As previously shown for rBoIFN-alpha 1, in vitro treatment of the AM with rBoIFN-gamma "activated" the AM as judged by enhanced cytotoxicity, enhanced accessory cell activity in mitogen-driven lymphocyte-proliferation, enhanced IgG Fc- and C3b-receptor expression and content of some enzymes. The fact that the two IFNs have very similar effects on cell functions, but differ markedly in their Ia-inducing immunoregulatory activity, supports the notion that the Ia-antigen expression may be irrelevant as a surface marker for macrophage activation, and may rather be a marker for a certain functional stage of the macrophage. Moreover, the acquisition of this stage appears to be, at least in the AM, a reversible event.

Infection of DBA/2 or C3H/HeJ mice by intraperitoneal injection of vaccinia virus elicits activated macrophages, cytolytic and cytostatic for S91-melanoma tumor cells

Murine peritoneal macrophages harvested 3-4 days after IP injection of vaccinia virus lysed S91-melanoma tumor cells in vitro; enhanced tumoricidal activity was measured with effector macrophages prepared 5-6 days after vaccinia virus infection. Treatment of virus-elicited macrophages prepared from DBA/2 mice with anti-asialo-GM1 antiserum, anti-Thy 1.2 antiserum or anti-Iad antiserum in the presence of complement so that cells sensitized with antibodies were lysed, did not reduce the measured level of tumoricidal activity indicating that macrophages [Ia(-); asialo GM1(-)] and not natural killer cells [asialo GM1(+); Thy 1.2(+/-)] or T-cells [Thy 1.2(+)] were responsible for mediating the lysis of S91-melanoma tumor cells. When incubated with virus-elicited macrophages but not thioglycollate-elicited macrophages, the ability of S91-melanoma tumor cells. to synthesize DNA was completely blocked. The results of these experiments support the view that one aspect of antitumor immunity enhanced during immunotherapy with vaccinia virus is the activation of macrophages which have cytolytic as well as cytostatic effects on melanoma tumor cells.

Analysis of peritoneal macrophages in continuous ambulatory peritoneal dialysis patients

Peritoneal macrophages (PMC) from patients undergoing continuous ambulatory peritoneal dialysis (CAPD) were compared to peritoneal macrophages from healthy volunteers and to peripheral blood monocytes (PBM) from CAPD patients, hemodialysis patients, and healthy volunteers. PMC from CAPD patients had morphology similar to PMC and PBM from healthy volunteers. HLA-DR antigen and Fc receptors were present on the cell surface. These monocytes had similar sequential morphologic changes in long-term culture compared to PBM from healthy volunteers. Phagocytosis, hydrogen peroxide generation and bactericidal activity were the same in PMC from CAPD patients as in PBM from healthy volunteers. Chemotaxis and eicosanoid precursor uptake studies suggest that PMC from CAPD patients may be relatively immature bone-marrow-derived cells. Although these cells function well as phagocytes, further study is warranted to define their immune competence, many components of which develop during differentiation into mature macrophages and may therefore be deficient in patients undergoing CAPD.

The acquisition of anti-influenza virus activity by macrophages

Exposure of resident peritoneal macrophages or thioglycollate-induced macrophages (TG-Mø) to influenza or Sendai virus-infected spleen cell culture supernatants (MAS) resulted in macrophage activation. When normal resident macrophages were used as effector cells, both infected P815 and L929 cells were lysed in the presence of MAS. MAS-activated TG-Mø also lysed influenza virus-infected L929 cells. Histocompatibility between effector cells and target cells was not required for target cell destruction. The effector cells were plastic-adherent, phagocytic and Ia-. MAS-activated macrophages were also resistant to influenza virus infection in vitro. Both infectious and non-infectious preparations of influenza or Sendai virus preparations were effective at generating MAS. The mediator(s) which renders macrophages to become cytotoxic and resistant to infection was acid-stable, heat-labile (56 degrees C, 30 min; or 100 degrees C, 5 min), and the activity was neutralized by sheep antimouse type 1 interferon (IFN).

The role of the macrophage in cardiac allograft rejection in the rat

Macrophages (MO) are a well-recognized component of the cellular infiltrate in first-set (acute) allograft rejections. Definition of their actual role in the mediation of rejection depends on showing that they are present in sufficient numbers and at relevant sites in rejecting grafts, that they are capable of mediating damage to graft tissues, and that their absence interfere with rejection. We have used rat heart allografts to investigate these questions. Normal rejection takes 7 days. By this time the MO is the major infiltrating cell and large numbers are present close to myocardial cells. In some cases they appear to push pseudopodia into the cell. Neither they, or other cell types, appear to be interacting with endothelial cells. MO extracted from rejecting allografts are potent secretors of plasminogen activator but show poor glass adherence and phagocytic ability compared to resident peritoneal cells. Graft MO are able to damage beating heart cells in vitro; their activity is not immunologically specific. Peritoneal MO from rats immunised with allogeneic spleen cells and MO grown in vitro from bone marrow in the absence of allostimulators behave similarly. Manipulation of MO behaviour was attempted with rabbit anti-rat MO serum. This did not prolong allograft survival and did not significantly depress blood monocyte levels. 750 rads irradiation prolonged graft survival usually until the death of the animal. Rejection could be restored with small lymphocytes from a normal rat, and the addition of bone-marrow cells had no effect. However, hearts rejected by animals given irradiation and lymphocytes alone contained as many MO as those rejected by normal animals, despite a reduction in blood monocyte levels to less than 5% of normal. We conclude that MO are present in large numbers and at relevant sites in rejecting allografts, and that they show features of activation and have a cytotoxic capability against relevant target cells. However, present approaches available for the prevention of MO accumulation in rejecting allografts are inadequate and, thus, no definitive statements about the need for MO as an effector cell in allograft rejection can be made.