The role of the liver in immunity to blood-stage murine malaria.

Mice vaccinated with fixed parasitized red blood cells and Bordetella pertussis can clear an otherwise lethal Plasmodium yoelii infection in 7 days; this protection is abolished by splenectomy before vaccination. Most mice splenectomized following vaccination were able to clear their infections, although their recovery was delayed. When labelled parasitized red cells were injected into mice during an infection, splenic uptake fell from day 3 onwards while uptake by the liver increased. Lymphocytes (mainly T cells) formed the majority of the live cells extracted from livers 7 days after infection, although blasts and myeloid cells were also present. Infected livers from vaccinated mice contained most cells. Less marked increases were observed 7 days after P. berghei infection of vaccinated mice. Examination of liver tissue showed that the sinusoids contained increased numbers of cells and suggested that activation of Kupffer cells was occurring, particularly in vaccinated mice infected with P. yoelii. Homing experiments confirmed the increased trapping of various cells in livers of vaccinated mice infected with P. yoelii. These results suggest an important role for the liver in recovery from blood-stage malaria infection.     

In vivo activation of macrophage oxidative burst activity by cytokines and amphotericin B.

Alterations in macrophage oxidative burst activity following in vivo administration of recombinant murine gamma interferon (IFN-gamma), recombinant murine tumor necrosis factor alpha, and the antifungal antibiotic amphotericin B were investigated. Mice were given intraperitoneal injections of these agents alone and in combination, and the oxidative responses of their resident peritoneal macrophages to challenge with Histoplasma capsulatum or zymosan particles were measured 1 to 5 days later. Various degrees of enhanced oxidative burst activity were achieved following treatment with each agent. However, a synergistic response was observed only when mice were treated with the combination of recombinant murine IFN-gamma and amphotericin B. These results not only confirm the dual role of amphotericin as an antifungal agent and as an immunomodulator but also suggest that IFN-gamma may serve as a useful adjunct in the treatment of intracellular fungal infections.     

Relationships between oxidative metabolism, macrophage activation, and antilisterial activity

Previous reports from this laboratory have revealed that macrophages obtained from 7-day Listeria-immune mice elicited 15 h before harvest with heat-killed homologous microorganisms were able to kill Listeria monocytogenes while resident or elicited cells were not [14, 16]. In the present study, experiments were conducted to determine if phagocytosis-associated oxidative metabolic activity participates in the enhanced destruction of Listeria by activated macrophages. Investigations into production of oxygen radicals by zymosan-stimulated macrophages revealed that Listeria-immune antigen-elicited (LIAE) cells produced significantly more superoxide and hydrogen peroxide than did resident, thioglycolate, or Listeria antigen-elicited macrophages. Additionally, the percentage of nitroblue tetrazolium (NBT) dye positive cells following exposure to zymosan was maximal in the immune-elicited population. Utilizing a luminol-dependent assay, a short-term chemiluminescent (CL) burst was noted in phagocytizing macrophages. This response was greatest in the LIAE population that exhibited a tenfold increase in peak chemiluminescence over other cell types. Prolonged in vitro culture of these cells diminishes their capacity to generate oxygen radicals. Additionally, LIAE macrophages cultured in excess of 38 h exhibited a significant decrease in zymosan-stimulated hydrogen peroxide release while the decline in superoxide generation was minimal. A substantial diminution in the Listeria-stimulated CL response was also noted during this time period. However, phagocytosis of Listeria by LIAE cells failed to induce the level of oxygen metabolites seen when zymosan was used as the particulate stimulant. In addition, scavengers of oxygen radicals were found to be relatively ineffective in reducing the killing of L monocytogenes by immunologically activated macrophages in culture. It therefore appears that toxic oxygen species do not play a major role in the heightened killing of Listeria by activated macrophages.     

Independence of macrophage activation and expression of the alleles of the Ity (immunity to typhimurium) locus

These studies demonstrate that alleles at the Ity locus do not affect T cell-dependent activation of macrophages by Corynebacterium parvum. Using a genetic analysis involving mice expressing various combinations of the Ityr, Itys, Lpsd, and Lpsn alleles we also show that the expression of the Ity alleles is not dependent on the ability of LPS to active macrophages. Since macrophage activation is though to be important in the killing of salmonella, these findings favor a mechanism of action of the Ity locus that does not involve bacterial killing.     

The role of T cells in pathogenesis and protective immunity to murine malaria.

T-cell-mediated immunity to a virulent strain of Plasmodium berghei NK65 (Pb NK65) and to an attenuated derivative (Pb XAT) of the strain were examined in CBA mice by the administration of monoclonal antibodies against T-cell subsets or interferon-gamma (IFN-gamma). The injection of anti-CD8+ or anti-IFN-gamma delayed the mortality of mice infected with Pb NK65, although it did not affect the parasitaemia. In the late stage of PB NK65 infection, T cells, especially CD8+ T cells, were increased in number in the liver at the expense of splenic CD8+ T cells. These CD8+ T cells released IFN-gamma in culture without antigen stimulation and were thought to induce tumour necrosis factor-alpha (TNF-alpha) production by the cells in the liver. In mice infected with Pb XAT, or mice primed with Pb XAT and then challenged with Pb NK65, CD4+ T cells had a crucial role in preventing parasite growth and in protective immunity. IFN-gamma was again the key molecule in protective immunity. These results suggest that T cells stimulated with malaria antigen play important roles both in protective immunity and pathogenesis depending upon their subsets; CD8+ T cells in pathogenesis, and CD4+ T cells in protective immunity. These apparently contradictory responses may be mediated by the same cytokine, IFN-gamma.     

Chemokine receptors and their role in leukocyte activation

Chemokines were originally isolated based on their abilities to selectively attract and recruit leukocyte populations. Over the last few years there has been an explosion in the number of new chemokines identified, and as a result many receptors previously considered to be orphans have now been paired up with their ligands. Here we review some of the latest results in this area, illustrating with data from our laboratory. The central question from a drug discovery perspective, is to show whether inhibiting chemokine receptors leads to a change in disease status. Although we are still a long way from having candidate molecules to take into the clinic, a flavour of what may be possible can be inferred from mutant chemokines with antagonistic properties. We discuss recent data using two of these proteins, Met-RANTES which has anti-inflammatory properties, and AOP-RANTES which has been shown to prevent infection of macrophages and T-cells by M-tropic HIV strains.     

Cell-mediated immunity to orbital tissue antigens in thyroid-associated ophthalmopathy determined using the leukocyte procoagulant activity assay.

While it is generally accepted that thyroid-associated ophthalmopathy (TAO), a progressive inflammatory disorder of the extraocular muscle and orbital connective tissue (OCT), is immunologically mediated the nature of the underlying abnormalities is poorly understood. Although there is considerable evidence for antibody-mediated immunity against both eye muscle (EM) and OCT antigens in TAO a role of cell-mediated immunity (CMI) has not been studied in detail. We have used a new sensitive test for CMI, the leukocyte procoagulant activity (LPCA) assay and tested blood leukocytes from patients with TAO and autoimmune thyroid disease (ATD) without evident ophthalmopathy for reactivity against pig eye muscle (PEM) and human thyroid and OCT membrane and soluble fractions. In some cases human EM fractions were also tested. Preparations of PEM membrane (PEMM) and human thyroid membrane induced a significant LPCA response in both groups of patients. PEM cytosol, human OCT membrane and cytosol and human spleen membrane did not evoke a significant response in either group of patients. There were significant positive correlations in patients with TAO between (i) LPCA in response to PEMM and that to human thyroid membrane and (ii) LPCA in response to human thyroid membrane and that to human EM membrane. In patients with TAO there were no significant associations between LPCA response to PEMM and the detection of serum antibodies to a 64 kDa EM membrane protein in immunoblotting, or between LPCA response to PEMM and the duration or severity of the ophthalmopathy or clinical evidence for eye muscle involvement. These findings confirm a role of cell-mediated immunity against eye muscle antigens in thyroid-associated ophthalmopathy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood monocyte oxidative burst activity in acute P. falciparum malaria

The release of superoxide anion from blood monocytes was studied in eight patients with acute primary attack P. falciparum malaria. Before treatment a significant enhancement of the oxidative burst prevailed, which contrasts with previous findings of a depressed monocyte chemotactic responsiveness. During treatment and after clinical recovery the activity of superoxide anion release normalized in all patients.     

The role of macrophage activation in chronic inflammation

The macrophage is the characteristic cell type in chronic inflammatory reactions, in the rheumatoid synovium, as in other sites. When macrophages are activated, considerable synthesis of enzymes and other proteins occurs. Macrophages can be activated by (i) products of activated lymphocytes, (ii) immune complexes and (iii) the complement cleavage product C3b. Among the many consequences of macrophage activation are (i) secretion of hydrolytic enzymes, (ii) cleavage of C3 into C3a, which is cytolytic, and C3b, (iii) production of tissue thromboplastin, a powerful procoagulant, and (iv) formation of polyamine oxidase, which in the presence of appropriate substrates generates factors that lyse or limit the proliferation of tumour cells, lymphocytes and micro-organisms. The relevance of these observations to the pathogenesis of chronic inflammatory reactions is discussed.     

Antibody-independent immunity to reinfection malaria in B-cell-deficient mice.

Immunity to "reinfection malaria" or "premunition" was studied in B-cell-deficient mice which had previously experienced acute malaria caused by the avirulent plasmodia Plasmodium yoelii or P. chabaudi or by the lethal P. vinckei. Such mice resisted challenge infection with large numbers of homologous parasites but differed in their capacity to resist challenge with heterologous species. Mice immune to P. yoelii resisted infection with P. chabaudi but developed acute-type, albeit nonlethal, infections when challenged with P. vinckei. Whereas mice immune to P. chabaudi resisted challenge with P. vinckei and vice versa, they developed fulminating malaria and died when infected with P. yoelii. The data suggest that immunity to reinfection malaria in B-cell-deficient mice, although antibody independent, is mediated by different mechanisms of resistance depending upon the plasmodial species used to initiate acute infection. Additional evidence supporting this concept was gained from preliminary experiments in which immunity to reinfection was measured by the ability of chronically infected mice to control endogenous parasites at low levels. B-cell-deficient mouse strains showed genotypic differences in their ability to develop immunity to reinfection with P. yoelii. In contrast, the same mouse strains uniformly developed immunity to reinfection with P. chabaudi. These findings suggest that different genetic loci control resistance to reinfection malaria caused by different species of plasmodia. Finally, B-cell-deficient mice acutely infected with lethal plasmodia, P. vinckei or P. berghei, died at the same time or earlier than similarly infected immunologically intact mice, indicating that "early death" in virulent malarial infections is an antibody-independent phenomenon.     

T-cell immunity in murine malaria: adoptive transfer of resistance to Plasmodium chabaudi adami in nude mice with splenic T cells.

Acute infections caused by the murine malarial parasite Plasmodium chabaudi adami are resolved by antibody-independent mechanisms of immunity. The fact that athymic nude mice developed high-grade unrelenting malaria and died when infected with this parasite suggested a significant role for T lymphocytes. Using adoptive transfer techniques, we demonstrated that spleen cells from either nonimmune or immune donor BALB/c mice eventually suppressed P. chabaudi adami infections in histocompatible recipient nude mice in a dose-dependent manner. Infections in recipients of "immune" spleen cells were less severe, demonstrating a depressed peak parasitemia and a shortened duration of patent infection, than was observed in recipients of normal spleen cells. Also, when sufficient numbers of immune spleen cells were transferred, the second wave of parasitemia (characteristic of this infection in nonimmune mice) failed to occur. T lymphocytes mediated protection in recipient mice, since T-cell-enriched, but not B-cell-enriched, spleen cell fractions suppressed P. chabaudi adami infections in nude mice. Protection was best achieved with T cells that bore the L3T4 phenotype. Patent parasitemias developed in all recipient mice, suggesting that the grafted cells did not limit parasite growth directly but achieved this end by activating other as yet unidentified inhibiting cell systems.     

The immune response in cirrhotic rats. Antigen distribution, humoral immunity, cell-mediated immunity and splenic suppressor cell activity.

The immunological disturbances occurring as a result of liver disease have been studied in an animal model of cirrhosis. The mononuclear phagocytic cells of the normal liver phagocytose large amounts of antigen irrespective of whether that antigen is injected directly into the portal or into the systemic circulations. The liver therefore acts as a filter 'in series' and 'in parallel' with the spleen and reduces the immunogenicity of antigens entering the organism by either of these routes. In rats with hepatic cirrhosis, there is a reduction in the capacity of the liver to phagocytose the flagellar antigen of Salmonella adelaide. This results in increased stimulation of splenic lymphoid tissue and in an increased antibody response to this thymus-independent antigen. The increased antigenic stimulus to the spleen may also be responsible for the increased suppressor-cell activity which has been demonstrated in these rats, and may be the mechanism of the diminished cell-mediated immune response both in this animal model of cirrhosis and in the human disease state. These studies suggest that many of the immunological disturbances associated with chronic liver disease may be the result of maldistribution of antigen occurring because of impaired hepatic phagocytic capacity.     

The role of hydrogen sulphide signalling in macrophage activation

Hydrogen sulphide (H₂S) is the latest identified small gaseous mediator enabled by its lipophilic nature to freely permeate the biological membranes. Initially, H₂S was recognized by its roles in neuronal activity and vascular relaxation, which makes it an important molecule involved in paracrine signalling pathways. Recently, the immune regulatory function of gasotransmitters, H₂S in particular, is increasingly being appreciated. Endogenous H₂S level has been linked to macrophage activation, polarization and inflammasome formation. Mechanistically, H₂S‐induced protein S‐sulphydration suppresses several inflammatory pathways including NF‐κB and JNK signalling. Moreover, H₂S serves as a potent cellular redox regulator to modulate epigenetic alterations and to promote mitochondrial biogenesis in macrophages. Here in this review, we intend to summarize the recent advancements of H₂S studies in macrophages, and to discuss with focus on the therapeutic potential of H₂S donors by targeting macrophages. The feasibility of H₂S signalling component as a macrophage biomarker under disease conditions would be also discussed.     

巨噬细胞移动抑制因子对固有免疫的调节作用

长期以来,巨噬细胞移动抑制因子(MIF)一直是一种功能不明的细胞因子.最近几年的研究发现,MIF是宿主抗微生物预警系统和应急反应(可以促进免疫细胞促炎症功能)的一个必要组成成份,是一种对固有免疫反应具有关键性调节作用的重要分子.研究表明,MIF参与了包括脓毒症、炎症和自身免疫性炎症疾病在内的一系列疾病的发病机制,这为未来使用靶向MIF疗法治疗相关的人类疾病提供了全新的思路.     

The role of macrophage activation and of Bcg-encoded macrophage function(s) in the control of Mycobacterium avium infection in mice.

Following the intraperitoneal inoculation of 2.5 x 10(8) colony-forming units of Mycobacterium avium strain ATCC 25291, there was bacillary growth in the liver, spleen and peritoneal cavity of C57BL/6, C57BL/10, DBA/1 and BALB/c mice whereas DBA/2, C3H/He, CBA/Ca and CD-1 mice controlled the infection showing constant or slightly decreasing numbers of viable bacteria in the liver and spleen and effective clearance of the bacilli from the peritoneal cavities. The acquisition of non-specific resistance (NSR) to Listeria monocytogenes during the infection by M. avium was high in C57BL/6, BALB/c and C3H/He mice and negligible in DBA/2 and CD-1 mice. The magnitude of the acquisition of NSR was reduced in T cell-deficient mice and was directly proportional to the dose of the inoculum of M. avium. The production of hydrogen peroxide by phorbol myristate acetate-stimulated peritoneal macrophages of M. avium-infected mice was higher in C57BL/6 and BALB/c mice than in CD-1, DBA/2 and C3H/He animals. BALB/c. Bcgr (C.D2) mice, unlike their congenic strain BALB/c, restricted bacterial growth following the intravenous inoculation of 2.5 x 10(8) CFU of M. avium as efficiently as DBA/2 mice. C.D2 and BALB/c peritoneal macrophages from infected mice produced similar amounts of H2O2 but BALB/c mice developed higher levels of NSR to listeria than C.D2 mice. The production of nitrite by peritoneal macrophages from infected mice was found to be enhanced in DBA/2 and C3H/He but not in BALB/c, C57BL/6, DC-1 and C.D2 mice. Resident peritoneal macrophages from C.D2 mice were more bacteriostatic in vitro for M. avium than macrophages from BALB/c mice. The same relative differences between the two macrophage populations were observed when the cells were activated with lymphokines. The results show that the populations were observed when the cells were activated with lymphokines. The results show that the resistance to M. avium infection in mice is under the control of the Bcg gene and that susceptibility may be due to some defect in macrophage antibacterial function not completely overcome by the activation of this phagocyte in the susceptible strains of mice.