Increased activity of FIM in serum of mice during a Mycobacterium bovis (BCG) infection.

In mice given an intravenous injection of Mycobacterium bovis (BCG), the bacilli proliferated in the spleen, liver and lungs but the peritoneal cavity remained sterile. The numbers of blood monocytes and alveolar macrophages were increased during the first 2 weeks of the infection, whereas the number of peritoneal macrophages remained constant. To study whether factor-increasing monocytopoiesis (FIM) plays a role in the regulation of the monocytosis during the BCG infection, the activity of this factor in the serum of mice at various intervals during the infection was determined. Previous studies have shown that FIM stimulates monocyte production by its effect on the mitotic activity of monoblasts and promonocytes in the bone marrow. The FIM activity of the serum reached a maximum on Day 4 and remained elevated during the first 21 days of the BCG infection. Since FIM is synthesized and secreted by macrophages that have phagocytosed opsonized particles, it is highly probable that FIM occurring in serum originates from macrophages that have ingested BCG. The results of the present study led to the conclusion that FIM plays a role in the monocytosis developing during infection with BCG.     

A novel rat monoclonal antibody reactive with murine tumoricidal Kupffer cells and activated peritoneal macrophages from BCG-infected mice

A rat monoclonal antibody, termed 1A2.10D and raised against mouse BCG-activated peritoneal-macrophages, was used to detect antigenic determinant(s) on mouse tumoricidal activated peritoneal and liver macrophages from BCG-infected mice by indirect immunofluorescence flow cytometry and immunoblot analysis. This antibody was of the rat IgG2b subclass and not cytolytic to BCG-activated macrophages in the presence of rabbit complement. The antigen(s) was expressed on tumoricidal activated peritoneal and liver macrophages from BCG-infected mice and some macrophage cell lines. Its expression could not be detected on resident peritoneal cells, peritoneal exudate cells containing non- or low tumoricidal macrophages, thymocytes, resting bone marrow cells, normal spleen cells, various established mouse tumour cells or one macrophage cell line. Immunoblot analysis showed the antibody to bind to one major protein of 56,000 MW, and to be expressed on the peritoneal and liver macrophages from BCG-infected mice. Using this antibody and a fluorescence-activated cell sorter, selection was made of antibody-positive or -negative macrophages from BCG-infected mice to examine their tumour killing activity. The antibody-positive macrophages clearly showed higher tumour killing activity than the negative macrophages.     

Spleen cell transfer induces T cell-dependent granulomas in tuberculous nude mice

After IV infection with an attenuated strain of Mycobacterium bovis BCG, athymic nude mice produced a few hepatic granulomas; most of the other foci of bacterial parasitization lacked obvious cellular reactions. Nude mice BCG-infected four weeks earlier received spleen cells from normal euthymic littermates. After transient splenomegaly which peaked at about two weeks, numerous hepatic granulomas appeared by four weeks and the number of viable BCG decreased. The development of hepatic granulomas required viable spleen cells and depended on the spleen cell dose and corresponded with positive footpad reactions. The effective population seemed to be T cells, since they were sensitive to treatment with anti-brain associated theta antigen serum (antiBAT) plus complement, and were found in nylon-wool passed fractions. After transfer with sensitized spleen cells, adoptive immunity was observed, provided that the recipient BCG-infected nude mice had been splenectomized before transfer. AntiBAT plus complement treatment of the sensitized spleen cells decreased the granuloma-producing as well as antimycobacterial capacity. When BCG-infected nude mice were irradiated with 500 r of gamma ray, granuloma production was decreased after immune spleen cell transfer. Co-transfer of immune spleen cells with normal nude mouse bone marrow cells to BCG-infected irradiated nude recipients restored the granuloma-forming ability.     

Role of interleukin-18 (IL-18) in mycobacterial infection in IL-18-gene-disrupted mice

Immunity to mycobacterial infection is closely linked to the emergence of T cells that secrete cytokines, gamma interferon (IFN-gamma), interleukin-12 (IL-12), and tumor necrosis factor alpha (TNF-alpha), resulting in macrophage activation and recruitment of circulating monocytes to initiate chronic granuloma formation. The cytokine that mediates macrophage activation is IFN-gamma, and, like IL-12, IL-18 was shown to activate Th1 cells and induce IFN-gamma production by these cells. In order to investigate the role of IL-18 in mycobacterial infection, IL-18-deficient mice were infected with Mycobacterium tuberculosis and Mycobacterium bovis BCG Pasteur, and their capacities to control bacterial growth, granuloma formation, cytokine secretion, and NO production were examined. These mice developed marked granulomatous, but not necrotic, lesions in their lungs and spleens. Compared with the levels in wild-type mice, the splenic IFN-gamma levels were low but the IL-12 levels were normal in IL-18-deficient mice. The reduced IFN-gamma production was not secondary to reduced induction of IL-12 production. The levels of NO production by peritoneal macrophages of IL-18-deficient and wild-type mice did not differ significantly. Granulomatous lesion development by IL-18-deficient mice was inhibited significantly by treatment with exogenous recombinant IL-18. Therefore, IL-18 is important for the generation of protective immunity to mycobacteria, and its main function is the induction of IFN-gamma expression.     

Growth of mycobacterium bovis (BCG) in T lymphocyte-depleted mice.

BCG Montreal (10-6 viable bacilli) injected intravenously into adult thymectomized, irradiated, and bone marrow-reconstituted (THXB) C57Bl times C3H F1 hybrid mice induced a progressive systemic infection which killed 95% of the animals within 60 days. Control mice infected with this dose of BCG did not die. The infected THXB mice failed to develop detectable levels of tuberculin hypersensitivity although they did show considerable Arthus (3 h) reactivity. The BCG-infected THXB mice lost weight progressively, and the root spleen and root lung indices increased substantially as the infection proceeded. None of the THXB mice developed an antibacterial immune response to the systemic BCG infection, and this was reflected by the continued persistence of macroscopic lung granuloma in these animals. The BCG-infected control mice developed as many surface tubercles as did the THXB animals, but the granulomas rapidly regressed in size and numbers in the normal mice. The lung changes correlated with the amount of tritiated thymidine incorporated by the lung cells in the later stages of the BCG infection. T cell depletion depressed the early splenic peak normally seen in BCG-infected controls, but, on the other hand, there was a progressive increase in lung counts in the THXB mice as the infection progressed and this late peak was not seen in the control animals. The significance of these findings is discussed in relation to the development of antituberculous immunity by BCG-infected mice.     

Correlation of Increased Metabolic Activity, Resistance to Infection, Enhanced Phagocytosis, and Inhibition of Bacterial Growth by Macrophages from Listeria- and BCG-Infected Mice

Macrophages from mice infected with facultative intracellular organisms such as Listeria monocytogenes and BCG have been shown to resist infection by antigenically unrelated intracellular bacterial parasites. This study compares phagocytosis, bacterial growth inhibition, and oxidation of glucose by macrophages from normal mice, mice infected with listeria or BCG, or mice immunized with killed listeria in incomplete Freund's adjuvant. Macrophages from listeria- and BCG-infected mice ingested more listeria; 67 and 57%, respectively, had three or more cell-associated bacteria versus 22% of controls (P < 0.001). Peritoneal macrophages from listeria- and BCG-infected animals significantly (P < 0.001 covariance analysis) inhibited growth of listeria in suspension, whereas control macrophages had no such inhibitory effect. The rate of oxidation of glucose-1-(14)C was higher in macrophages from listeria- and BCG-infected mice than from either uninfected animals or those immunized with killed listeria. During phagocytosis of killed or live bacteria, or latex particles, the rate of glucose oxidation was increased (P < 0.01). These data suggest that the cellular immunity after infection by an intracellular organism is associated with an increase in metabolic activity of macrophages, namely, an increase in the rate of glucose oxidation resulting in enhancement of phagocytosis and killing.     

Microbicidal activities of Salmonella typhimurium- and interferon-gamma-activated mouse peritoneal macrophages

Activation of mouse peritoneal macrophages during infection of mice by various facultative intracellular bacteria and after intravenous injection of recombinant interferon-gamma (rIFN-gamma) was studied. Macrophage activation was demonstrated on the basis of three different criteria, i.e. inhibition of Toxoplasma gondii proliferation, enhanced release of H2O2 and increased expression of Ia antigen. Macrophages activated during an infection with Salmonella typhimurium showed no enhanced salmonellacidal or listericidal activity relative to control macrophages, whereas Listeria-activated macrophages killed Listeria but not Salmonella faster than control macrophages. The rate of proliferation of Salmonella in spleen and liver of activated mice was comparable to the proliferation in the organs of control mice. rIFN-gamma-activated macrophages displayed neither an enhanced salmonellacidal nor an enhanced listericidal activity. When high numbers of Listeria were injected intravenously the proliferation in spleen and liver of rIFN-gamma-treated and control mice was similar. The proliferation of Listeria in the liver of rIFN-gamma-treated mice was less than in control mice when 1 LD50 or lower numbers of bacteria were injected. It is concluded that peritoneal macrophages become activated during infections of mice with various intracellular pathogens. However, these activated macrophages do not show enhanced bactericidal activity against all bacteria. Furthermore, rIFN-gamma is not sufficient to enhance the listericidal activity of macrophages.     

Granuloma formation and hemopoiesis induced by C36-48-mycolic acid-containing glycolipids from Nocardia rubra

As previously reported (I. Yano, I. Tomiyasu, S. Kitabatake, and K. Kaneda, Acta Leprologica 2:341-349, 1984), Nocardia rubra, one of the nonpathogenic actinomycetes, possesses three classes of mycolic acid-containing glycolipid, i.e., glucose mycolate, trehalose dimycolate, and trehalose monomycolate. The carbon chain length of their mycolic acids is shorter (C36-48) than that in mycobacteria (longer than C70), and the glycolipid consists of only alpha-mycolic acid. One intravenous administration of 500 micrograms of each purified glycolipid to ICR mice in the form of water-in-oil-in-water emulsion without any protein antigens caused prominent granuloma formation in the lungs, spleen, and liver. The lung index in the treated mice was about 3.5 times larger than that in the control mice (given water-in-oil-in-water emulsion only) at 1 week after the injection and then rapidly declined, while spleen and liver indices peaked at 2 weeks after the injection and persisted longer. The granuloma consisted of macrophages, some of which phagocytized glycolipid micelles, lymphocytes, monocytes, and neutrophils. In addition, many small hemopoietic islands were observed in the liver sinusoids, where various immature blood cells were trapped by the prominent cytoplasmic projections of Kupffer cells. The granuloma formation and hemopoiesis observed here are considered to be the most characteristic morphological expression of macrophage activation in these organs. This is the first report to show that such histological changes can be induced by chemically defined and homogeneous mycolic acid-containing glycolipids other than those of mycobacteria.     

Role of macrophages in the development of arteritis in MRL strains of mice with a deficit in Fas-mediated apoptosis

The lpr and gld genes have been shown to encode the Fas antigen deletion mutant and the Fas ligand (FasL) mutant, respectively. An MRL strain of mice bearing the gld gene was observed to spontaneously develop granulomatous arteritis, similar to that in mice bearing the lpr gene, indicating that arteritis in this strain is due to an inefficient Fas–FasL interaction resulting in an incapacity for Fas-mediated apoptosis. The arterial lesions in both strains were characterized by a remarkable perivascular accumulation of activated macrophages bearing Mac-2 antigen, following the infiltration of CD4⁺ cells, and this resulted in the destruction of the arterial wall. Almost all of these infiltrating cells were Fas-positive, as determined in MRL/gld mice. Macrophage colony-stimulating factor (M-CSF), which is present at increased levels in MRL/lpr mice, but not in MRL/Mp- +/+ (MRL/+) mice, induced the expression of Mac-2 antigen and Fas antigen on spleen adherent cells of MRL/+ mice. Moreover, continuous infusion of M-CSF into the peritoneal cavity or subcutis of MRL/+ mice induced the release of oxygen radicals of peritoneal macrophages or granuloma formation associated with the massive accumulation of Mac-2+ cells, respectively. These findings suggest that macrophages in these mice, which may be activated by M-CSF and may avoid Fas-mediated apoptosis, play a critical role as effector cells in the destruction of arterial wall.     

Effect of Mycobacterium tuberculosis BCG infection on the resistance of mice to ectromelia virus infection: participation of interferon in enhanced resistance.

Mice infected with Mycobacterium tuberculosis BCG were more resistant than normal mice to ectromelia virus infection. It is suggested that enhanced interferon production in peritoneal exudate cells and spleen cells of BCG-infected mice plays an important role in this resistance.     

Immunosuppressive effect of cyclosporin A on Mycobacterium bovis BCG infections in mice.

The effect of increasing doses of cyclosporin A (CsA) given to mice infected intravenously with Mycobacterium bovis BCG was investigated. Development of both tuberculin hypersensitivity and acquired antituberculous resistance was suppressed in a dose-responsive manner. Daily dosages at 100 mg/kg of body weight prevented any reduction in the BCG counts within the lungs, liver, or spleen. This effect was associated with lowered nonspecific resistance to a Listeria monocytogenes challenge and a decline in specific protective immunity adoptively transferred to naive recipients. CsA treatment had no effect on antilisterial activity by activated macrophages or on the antituberculous immunity expressed by specific memory T cells. CsA treatment inhibited the ability of BCG-vaccinated mice to produce gamma interferon (IFN-gamma) after a secondary stimulation with live BCG or with lipopolysaccharide. Spleen cells from BCG-infected mice which were exposed to daily treatment with CsA showed reduced IFN-gamma production in response to purified protein derivative or concanavalin A stimulation, suggesting that the immunosuppressive effect of CsA on BCG-infected mice was expressed by inhibiting the development of effector T cells responsible for the production of IFN-gamma.     

Effect of granulocyte-macrophage colony-stimulating factor on the number of leucocytes and course of Listeria monocytogenes infection in naive and leucocytopenic mice.

This study concerns the effect of recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) on the number of circulating leucocytes, activation of peritoneal macrophages and proliferation of Listeria monocytogenes in various organs of naive and leucocytopenic mice. Mice were rendered leucocytopenic by sublethal total body irradiation or cyclophosphamide treatment. GM-CSF treatment enhanced the number of granulocytes and monocytes in peripheral blood during L. monocytogenes infection in naive mice, but not in irradiated or cyclophosphamide-treated mice. In naive mice, irradiated and cyclophosphamide-treated mice, GM-CSF did not affect the course of L. monocytogenes infection in thigh muscle, spleen and liver. However, GM-CSF treatment significantly increased the number of macrophages in the peritoneal cavity of naive mice during infection; these macrophages were more enlarged and showed a higher frequency of binucleated and multinucleated cells relative to non-GM-CSF-treated mice. Together, these results demonstrated that GM-CSF increased the number of circulating granulocytes and monocytes, and the number of peritoneal macrophages during infection with L. monocytogenes in naive mice, but did not affect the course of the infection in thigh muscle, spleen or liver of these mice. In leucocytopenic mice, however, GM-CSF did not affect the number of circulating phagocytes, which explains that this factor had no effect on the proliferation of the bacteria in the various organs.     

Impaired IL-15 production associated with susceptibility of murine AIDS to mycobacterial infection

LP-BM5 murine leukemia virus (MuLV) injection causes murine AIDS (MAIDS), a disease characterized by many functional abnormalities of immunocompetent cells. We show that MAIDS mice are susceptible to Mycobacterium bovis Bacille Calmette-Guérin (BCG) infection as assessed by survival rate and bacterial counts. The peritoneal exudate macrophages from MAIDS mice produced a significant level of interleukin (IL)-12 soon after inoculation with BCG, whereas IL-15 and tumor necrosis factor (TNF) production were severely impaired in BCG-infected MAIDS mice. The appearance of natural killer (NK) and CD4+ T helper type 1 (Th1) cells specific for mycobacterial antigen were depressed in MAIDS mice after BCG infection. Thus, it appeared that impaired production of IL-15, besides other inflammatory cytokines, in MAIDS mice may be involved in the poor responses of the NK and Th1 cells, resulting in an increased susceptibility to BCG.     

Identification and characterization of a BCG antigen expressed at the membrane surface of in vitro infected mouse peritoneal macrophages.

A murine monoclonal antibody to Mycobacterium bovis (BCG) (230A4A6) was used to identify an antigenic determinant expressed at the surface of murine peritoneal macrophages infected in vitro. This determinant was shown to be expressed with a delay in infected macrophages following in vitro infection. Isolation of the 230A4A6 reactive antigen showed that it was part of a 12-kD molecule. This protein was shown to be capable of eliciting delayed-type hypersensitivity in infected mice in a standard footpad assay as well as provide stimulus for mitogenesis of BCG-primed spleen cells.     

Neutrophils play a protective nonphagocytic role in systemic Mycobacterium tuberculosis infection of mice

Evidence showing that neutrophils play a protective role in the host response to infection by different intracellular parasites has been published in the past few years. We assessed this issue with regard to the infection of mice with Mycobacterium tuberculosis. We found a chronic recruitment of neutrophils to the infection foci, namely, to the peritoneal cavity after intraperitoneal infection and to the spleen and liver after intravenous inoculation of the mycobacteria. However, bacilli were never found associated with the recruited neutrophils but rather were found inside macrophages. The intravenous administration of the antineutrophil monoclonal antibody RB6-8C5 during the first week of infection led to selective and severe neutropenia associated with an enhancement of bacillary growth in the target organs of the mice infected by the intravenous route. The neutropenia-associated exacerbation of infection was most important in the liver, where a bacterial load 10-fold higher than that in nonneutropenic mice was found; the exacerbation in the liver occurred both during and after the neutropenic period. Early in infection by M. tuberculosis, neutropenic mice expressed lower levels of mRNAs for gamma interferon and inducible nitric oxide synthase in the liver compared to nondepleted mice. These results point to a protective role of neutrophils in the host defense mechanisms against M. tuberculosis, which occurs early in the infection and is not associated with the phagocytic activity of neutrophils but may be of an immunomodulatory nature.     

Role of tumor necrosis factor-alpha in Mycobacterium-induced granuloma formation in tumor necrosis factor-alpha-deficient mice

To study the role of TNF-alpha in mycobacterial infection, we generated TNF-alpha-knockout (KO) mice, in which the third and fourth exons of the TNF-alpha gene were disrupted. The C57BL/6 KO mice were injected with virulent Mycobacterium tuberculosis strain Kurono or avirulent bacillus Calmette-Guérin (BCG) Pasteur (10(6) colony-forming units), through the tail veins. The major organs were removed at weekly intervals, and morphologic observation, assays of IL-1, IL-12, IFN-gamma, and inducible nitric oxide synthase mRNA expression, and colony counts in the lungs and spleen were performed. Peritoneal macrophages from BCG- and H37Rv strain-treated mice produced significant levels of nitric oxide after stimulation in vitro. Formation of abscesses was seen only in the Kurono-treated groups, and these abscesses contained large numbers of mycobacteria. The administration of recombinant TNF-alpha significantly ameliorated the mycobacterial lesions. IFN-gamma mRNA was expressed significantly in virulent H37Rv-treated groups with time, and the number of mycobacterial colonies per unit weight increased remarkably with time. Nitric oxide production was not observed in H37Rv-treated groups but was seen in BCG-treated groups. We concluded that TNF-alpha played an important role in protective immunity against virulent mycobacteria. Because avirulent mycobacteria did not induce granulomas in TNF-alpha-KO mice, TNF-alpha played an indirect role in granuloma formation.     

Further study on relationship of anti-tuberculous protection to lung granulomata produced by intravenous injections of synthetic 6-0-mycoloyl-N-acetyl-muramyl-L-alanyl-D-isoglutamine with or without specific antigens.

The synthetic adjuvant, 6-0-mycoloyl-n-acetylmuramyl-L-alanyl-D-isoglutamine (mycol-MDP), is know to have a similar activity to the adjuvant moiety which resides in BCG cell walls (CW). Mycol-MDP plus a specific antigen, PPD, produced lung granulomata followed by anti-tuberculous protection in BCG CW high responder C57BL/6 (B6) mice, but not in low responder C3H/HeMs) (C3H) mice when a granuloma assay and an aerosol challenge with Mycobacterium bovis, Ravenel were carried out 4 weeks after the injection. However, when the granuloma assay and mycobacterial infection were performed 1 week after the injection, both B6 and C3H mice showed slight but definite lung granuloma formation accompanied by detectable protection. This suggested that the early development of granuloma was elicited by direct activation of macrophages with mycol-MDP. This possibility was confirmed since T-cell-deprived (B) mice produced lung granulomata 1 week after injection with mycol-MDP alone. However, contrary to our expectation, these B mice did not show anti-tuberculous protection. The role of T cells for anti-tuberculous immunity is discussed in relation to the adjuvant activity of mycol-MDP.     

Parallelism between superoxide production of peritoneal exudate cells and lung granulomatous response in mice vaccinated with BCG cell walls

Since peritoneal macrophages are reported to be different from alveolar macrophages in their activated states, we examined whether O-2 production, one of the parameters of macrophage activation, in mouse peritoneal exudate cells (PEC) is enhanced under the condition in which lung granuloma, the accumulation of activated macrophages, is produced with Bacillus Calmette-Guérin (BCG) cell wall (CW). As a result, we observed the enhanced O-2 production of PEC that occurs in parallel with lung granuloma formation; high responders, C56BL/6 mice, showed high O-2 production of PEC whereas low responders, C3H/He and DBA/1 mice showed low O-2 production of PEC, suggesting that enhanced O-2 production of PEC as well as lung granuloma formation is genetically controlled. Results from T cell-depleted mice and allogeneic bone marrow chimeric mice also showed the occurrence of this parallelism. From these findings, we presumed that circulating macrophage activating factor and other lymphokines produced by BCG CW-sensitized T cells may activate both peritoneal macrophages and lung macrophages.     

Macrophages in bronchoalveolar lavage fluid are not representative of macrophages in granulomas of the lungs of BCG-infected mice

To find out whether macrophages obtained by bronchoalveolar lavage (BAL) represent the macrophage population in alveoli, we performed a quantitative study to compare the expression of cell-surface antigens by macrophages in the lavage fluid as well as in the alveolar spaces of sectioned lung tissue from normal and BCG-infected mice. The amount of antigen on cells, determined with a quantitative immunocytochemical method, was expressed as the mean specific absorbance per 0.25 micron2 cell-surface area. In normal mice, BAL and intra-alveolar macrophages are identical. Macrophages in BAL fluid and intra-alveolar macrophages, both from BCG-infected mice, expressed antigen F4/80 and Fc receptor II to about the same extent, but the former showed a significantly higher level of antigen expression as defined by antibodies M1/70, M5/114, 30.G.12, and M3/38. In granulomatous lesions, expression of antigens by macrophages, assessed semi-quantitatively, was considerably less than that by BAL macrophages. Lymphocytes in the BAL fluid resembled those in the granulomas. These findings led to the conclusion that in BCG-infected mice, the macrophages found in BAL fluid do not resemble those occurring in either the alveoli or the granulomatous lesions of the lungs. On these grounds, the relevance of findings in BAL fluid to lung interstitial lung diseases should be reconsidered.