Lymphotoxin beta receptor signaling limits mucosal damage through driving IL-23 production by epithelial cells

The immune mechanisms regulating epithelial cell repair after injury remain poorly defined. We demonstrate here that lymphotoxin beta receptor (LTβR) signaling in intestinal epithelial cells promotes self-repair after mucosal damage. Using a conditional gene-targeted approach, we demonstrate that LTβR signaling in intestinal epithelial cells is essential for epithelial interleukin-23 (IL-23) production and protection against epithelial injury. We further show that epithelial-derived IL-23 promotes mucosal wound healing by inducing the IL-22-mediated proliferation and survival of epithelial cells and mucus production. Additionally, we identified CD4(-)CCR6(+)T-bet(-) RAR-related orphan receptor gamma t (RORγt)(+) lymphoid tissue inducer cells as the main producers of protective IL-22 after epithelial damage. Thus, our results reveal a novel role for LTβR signaling in epithelial cells in the regulation of intestinal epithelial cell homeostasis to limit mucosal damage.

Characterization of virulence, colony morphotype and the glycopeptidolipid of Mycobacterium avium strain 104

SETTING

Members of the Mycobacterium avium complex (MAC) are responsible for mycobacterial disease in children, the aged and in immunocompromised individuals. The complex consists of different species, serovars and morphologic forms that vary in virulence. One isolate of the MAC is currently being sequenced (MAC 104) and was chosen based on its derivation from an AIDS patient and the fact that it could be genetically manipulated.

OBJECTIVE

MAC 104 was therefore analyzed for virulence, colony morphotype and expression of the glycopeptidolipid (GPL) responsible for serotying differences and the rough to smooth morphological switch.

RESULTS

The isolate was found to be virulent in the murine model of low-dose aerosol infection in that it could colonize the lung, proliferate within the tissue and disseminate to other organs. MAC 104 expressed a variety of colony morphotypes, the most prevalent of which were smooth opaque, smooth transparent and rough. All three morphotypes could persist in the lung; however, the transparent and rough morphotypes grew more rapidlyinvivo. The rough morphotype was unusual in that it expressed an atypical form of the GPL usually absent from rough morphotypes.

CONCLUSION

This characterization complements the genome data and confirms that MAC 104 behaves similarly to other MAC isolates.

Cu,Zn superoxide dismutase of Mycobacterium tuberculosis contributes to survival in activated macrophages that are generating an oxidative burst

Macrophages produce reactive oxygen species and reactive nitrogen species that have potent antimicrobial activity. Resistance to killing by macrophages is critical to the virulence of Mycobacterium tuberculosis. M. tuberculosis has two genes encoding superoxide dismutase proteins, sodA and sodC. SodC is a Cu,Zn superoxide dismutase responsible for only a minor portion of the superoxide dismutase activity of M. tuberculosis. However, SodC has a lipoprotein binding motif, which suggests that it may be anchored in the membrane to protect M. tuberculosis from reactive oxygen intermediates at the bacterial surface. To examine the role of the Cu,Zn superoxide dismutase in protecting M. tuberculosis from the toxic effects of exogenously generated reactive oxygen species, we constructed a null mutation in the sodC gene. In this report, we show that the M. tuberculosis sodC mutant is readily killed by superoxide generated externally, while the isogenic parental M. tuberculosis is unaffected under these conditions. Furthermore, the sodC mutant has enhanced susceptibility to killing by gamma interferon (IFN-gamma)-activated murine peritoneal macrophages producing oxidative burst products but is unaffected by macrophages not activated by IFN-gamma or by macrophages from respiratory burst-deficient mice. These observations establish that the Cu,Zn superoxide dismutase contributes to the resistance of M. tuberculosis against oxidative burst products generated by activated macrophages.

Inflammation and lymphocyte activation during mycobacterial infection in the interferon-gamma-deficient mouse

Interferon-gamma is a pivotal cytokine in the protective response to tuberculosis. In its absence rampant bacterial growth results in tissue destruction and death. While macrophage activation is key, this pleiotropic cytokine has other secondary but significant roles. To investigate these roles, both intravenous and aerosol infection of the IFN-gamma gene disrupted (GKO) mouse was performed. For the first time we describe the very similar growth of bacteria, during the initial phase of infection, between control and GKO mice. During this initial phase, however, very different histopathologic consequences between control and GKO mice were observed. Key observations included an early increased accumulation of granulocytes and a much more rapid and pronounced interstitial pneumonia in the GKO mice. As infection developed, GKO mice mounted an antigen-specific response; however, lymphocyte activation was much more rapid in these mice. Of interest is the fact that this increased rapidity occurred prior to significant differences in bacterial number. Taken together these data support a role for IFN-gamma in limiting both initial cellular recruitment and acquired lymphocytic responses to mycobacterial infection. This role may be key in surviving the kind of chronic stimulatory disease caused by Mycobacterium tuberculosis.

CD95 signaling is not required for the down regulation of cellular responses to systemic Mycobacterium tuberculosis infection

There is a tendency among tuberculosis patients to have reduced cellular responses to mycobacterial antigens and this loss has been associated with apoptosis of CD4 T cells. In order to determine the role of CD95 in mediating apoptosis of antigen-specific lymphocytes in tuberculosis, mice with a mutated CD95L molecule were infected systemically with virulent Mycobacterium tuberculosis. Both control and CD95L mutant mice exhibited the expected loss of response to mycobacterial antigens, with the only difference being a slight delay in the loss of the response in the mutant mice. The limited persistence of the response in the mutant mice suggests that, while antigen-specific cellular responses do decline in mice infected with mycobacteria, this decline is not dependent upon CD95L.

Immunological basis for reactivation of tuberculosis in mice

In this study different inbred strains of mice appeared to control and contain a low dose aerosol infection with Mycobacterium tuberculosis in a similar manner, giving rise to a chronic state of disease. Thereafter, however, certain strains gradually began to show evidence of regrowth of the infection, whereas others consistently did not. Using C57BL/6 mice as an example of a resistant strain and CBA/J mice as an example of a strain susceptible to bacterial growth, we found that these animals revealed distinct differences in the cellular makeup of lung granulomas. The CBA/J mice exhibited a generally poor lymphocyte response within the lungs and vastly increased degenerative pathology at a time associated with regrowth of the infection. As a possible explanation for these events, it was then observed that the CBA/J mouse strain was also less able to upregulate adhesion molecules, including CD11a and CD54, on circulating lymphocytes. These results therefore suggest that a failure to control a chronic infection with M. tuberculosis may reflect an inability to localize antigen-specific lymphocytes within the lung.

CD8- and CD95/95L-dependent mechanisms of resistance in mice with chronic pulmonary tuberculosis

The role of CD8 T lymphocytes in the immune response to Mycobacterium tuberculosis infection remains enigmatic, with persuasive reports of both cytolytic and noncytolytic (cytokine-mediated) responses to infection. To address the importance of the cytolytic mechanisms, mice with targeted disruptions for CD8 and perforin or with gene mutations in the CD95/ CD95L signaling pathway were exposed to pulmonary infection. All mice tested showed no differences in their ability to contain the growth of infection during the early phase of disease. As the chronic phase of the disease ensued, however, both CD8- and CD95/CD95L-deficient mice gradually lost their ability to limit bacterial growth. This was associated with a tendency toward pyogenic inflammation in the lung. This tendency was not seen in the perforin gene-disrupted mice. In CD8 gene-disrupted mice, the ability to generate interferon-gamma secreting T cells was unimpaired. Although these cells were capable of entering the lung they were unable to influence the increasing bacterial load in this organ.

Expression of the nitric oxide synthase 2 gene is not essential for early control of Mycobacterium tuberculosis in the murine lung

The interleukin-12 and gamma interferon (IFN-gamma) pathway of macrophage activation plays a pivotal role in controlling tuberculosis. In the murine model, the generation of supplementary nitric oxide by the induction of the nitric oxide synthase 2 (NOS2) gene product is considered the principal antimicrobial mechanism of IFN-gamma-activated macrophages. Using a low-dose aerosol-mediated infection model in the mouse, we have investigated the role of nitric oxide in controlling Mycobacterium tuberculosis in the lung. In contrast to the consequences of a systemic infection, a low dose of bacteria introduced directly into the lungs of mice lacking the NOS2 gene is controlled almost as well as in intact animals. This is in contrast to the rapid progression of disease in mice lacking IFN-gamma or a key member of the IFN signaling pathway, interferon regulatory factor 1. Thus while IFN-gamma is pivotal in early control of bacterial growth in the lung, this control does not completely depend upon the expression of the NOS2 gene. The absence of inducible nitric oxide in the lung does, however, result in increased polymorphonuclear cell involvement and eventual necrosis in the pulmonary granulomas of the infected mice lacking the NOS2 gene.

Restraining mycobacteria: role of granulomas in mycobacterial infections

The generation of prolonged immunity to Mycobacterium tuberculosis requires not only an antigen-specific IFN-gamma-producing T cell response, including both CD4 and CD8 T cells, but also the generation of protective granulomatous lesions, whereby the close apposition of activated T cells and macrophages acts to contain bacterial growth. The importance of the granulomatous lesion in controlling this immune response and in limiting both tissue damage and bacterial dissemination has been considered a secondary event but, as the present review illustrates, is no less important in surviving mycobacterial infection than an antigen-specific T-cell response. The formation of a protective granuloma involves the orchestrated production of a host of chemokines and cytokines, the upregulation of their receptors along with upregulation of addressins, selectins and integrins to coordinate the recruitment, migration and retention of cells to and within the granuloma. In the present review, the principal components of the protective response are outlined and the role of granuloma formation and maintenance in mediating prolonged containment of mycobacteria within the lung is addressed.

A novel nonclassic beta2-microglobulin-restricted mechanism influencing early lymphocyte accumulation and subsequent resistance to tuberculosis in the lung

In this study, we compared the course of a low-dose aerosol Mycobacterium tuberculosis infection in mice bearing gene disruptions for the beta2-microglobulin molecule, the CD8 molecule, and the CD1 molecule. Over the first 50 d of infection, the CD8- and CD1-disrupted mice were no more susceptible to infection than were the control mice. In contrast, the bacterial load in beta2-microglobulin gene-disrupted mice increased rapidly and attained much higher levels than that observed in the other gene-disrupted mice and in control mice. A second major difference between the beta2-microglobulin gene-disrupted mice and the other animals was the development of lung granulomas; both the CD8- and CD1-disrupted mice developed essentially normal granulomas except for an apparent increased lymphocyte influx in the CD8-disrupted mice. The beta2-microglobulin gene-disrupted mice, on the other hand, developed granulomas virtually devoid of lymphocytes, with these cells instead localized within prominent perivascular cuffing adjacent to the lesions. These data support the hypothesis that a beta2-microglobulin-dependent, non-CD8- and non-CD1-dependent mechanism controls the early and efficient influx of protective lymphocytes into infected lesions, and that the absence of this mechanism decreases the capacity of the animal to initially deal with pulmonary tuberculosis.

Interleukin-6 induces early gamma interferon production in the infected lung but is not required for generation of specific immunity to Mycobacterium tuberculosis infection

Immunity to Mycobacterium tuberculosis is dependent upon the generation of a protective gamma interferon (IFN-gamma)-producing T-cell response. Recent studies have suggested that interleukin-6 (IL-6) is required for the induction of a protective T-cell response and that IL-4 may suppress the induction of IFN-gamma. To evaluate the role of the cytokines IL-6 and IL-4 in the generation of pulmonary immunity to M. tuberculosis, IL-6 and IL-4 knockout mice were infected with M. tuberculosis via aerosol. The absence of IL-6 led to an early increase in bacterial load with a concurrent delay in the induction of IFN-gamma. However, mice were able to contain and control bacterial growth and developed a protective memory response to secondary infection. This demonstrates that while IL-6 is involved in stimulating early IFN-gamma production, it is not essential for the development of protective immunity against M. tuberculosis. In contrast, while the absence of IL-4 resulted in increased IFN-gamma production, this had no significant effect upon bacterial growth.

Transient loss of resistance to pulmonary tuberculosis in p47(phox-/-) mice

Mycobacterium tuberculosis is an important respiratory pathogen the growth of which is controlled primarily by cytokine-activated macrophages. One of the principal mediators of this control is nitric oxide; however, superoxide has recently been shown to be protective in systemic mycobacterial infections. To determine whether superoxide is important in controlling M. tuberculosis during primary pulmonary infection, mice lacking the cytosolic p47(phox) gene (which is essential for effective superoxide production by the NADPH oxidase) were infected aerogenically. The lack of superoxide during an aerosol infection with M. tuberculosis resulted in a significant increase in bacterial growth over the early period of infection. Once antigen-specific gamma interferon-producing lymphocytes were detected in the draining lymph nodes, however, bacterial growth in the lung stopped. One interesting consequence of the lack of superoxide was an increase in neutrophilic infiltrates within the granuloma. This may be a consequence of increased tissue damage due to more rapid bacterial growth or may reflect a role for superoxide in controlling inflammation.

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.

Resistance of virulent Mycobacterium avium to gamma interferon-mediated antimicrobial activity suggests additional signals for induction of mycobacteriostasis

The cytokine gamma interferon (IFN-gamma) plays a major role in the control of Mycobacterium avium infections. We assessed whether the progressive growth of virulent strains of M. avium was associated with alterations in the production of this cytokine as evaluated by reverse transcription-PCR and detection of immunoreactive cytokine in the serum and in spleen homogenates. We found that IFN-gamma was induced during infection by a virulent strain of M. avium to similar or even higher extents than the levels found during infections by a less virulent strain whose growth was controlled. IFN-gamma produced during infection by both mycobacterial strains was partly derived from T cells and led to activation of macrophages, namely, those that were infected. Concomitant with the development of the infection with the virulent strain of M. avium there was an extensive depletion of lymphocytes in the spleen. Thymectomy alone promoted the proliferation of the virulent, but not of the less virulent, strain of M. avium. Our data indicate that virulent strains of M. avium resist the antimicrobial mechanisms of IFN-gamma-activated macrophages and raise the possibility that a second, T-cell-dependent signal is required for the effective control of mycobacterial replication inside macrophages.

Cytokine/chemokine cascades in immunity to tuberculosis

The relationship between acquired specific resistance and delayed-type hypersensitivity (DTH) in immunity to tuberculosis has long been a topic of debate. Here, Ian Orme and Andrea Cooper propose that the events are separate mechanisms; protection is cytokine driven and initially controls the infection, whereas DTH is primarily chemokine driven and functions to wall off the infection and prevent further dissemination.

Antimycobacterial activities of isoxyl and new derivatives through the inhibition of mycolic acid synthesis

Isoxyl (ISO), a thiourea (thiocarlide; 4, 4'-diisoamyloxythiocarbanilide), demonstrated potent activity against Mycobacterium tuberculosis H37Rv (MIC, 2.5 micrograms/ml), Mycobacterium bovis BCG (MIC, 0.5 microgram/ml), Mycobacterium avium (MIC, 2.0 microgram/ml), and Mycobacterium aurum A+ (MIC, 2.0 microgram/ml), resulting in complete inhibition of mycobacteria grown on solid media. Importantly, a panel of clinical isolates of M. tuberculosis from different geographical areas with various drug resistance patterns were all sensitive to ISO in the range of 1 to 10 microgram/ml. In a murine macrophage model, ISO exhibited bactericidal killing of viable intracellular M. tuberculosis in a dose-dependent manner (0.05 to 2.50 microgram/ml). The selective action of ISO on mycolic acid synthesis was studied through the use of [1, 2-14C]acetate labeling of M. tuberculosis H37Rv, M. bovis BCG, and M. aurum A+. At its MIC for M. tuberculosis, ISO inhibited the synthesis of both fatty acids and mycolic acids (alpha-mycolates by 91.6%, methoxymycolates by 94.3%, and ketomycolates by 91.1%); at its MIC in M. bovis BCG, ISO inhibited the synthesis of alpha-mycolates by 87.2% and that of ketomycolates by 88.5%; and the corresponding inhibitions for M. aurum A+ were 87.1% for alpha-mycolates, 87.2% for ketomycolates, and 86.5% for the wax-ester mycolates. A comparison with isoniazid (INH) and ethionamide (ETH) demonstrated marked similarity in action, i.e., inhibition of the synthesis of all kinds of mycolic acids. However, unlike INH and ETH, ISO also inhibited the synthesis of shorter-chain fatty acids. ISO showed no acute toxicity against primary macrophage cell cultures as demonstrated by diminution of redox activity. A homologous series of ISO derivatives were synthesized. Most derivatives were as effective or more effective than the parent compound in the agar proportion assay. Thus, these thioureas, like INH and ETH, specifically inhibit mycolic acid synthesis and show promise in counteracting a wide variety of drug-sensitive and -resistant strains of M. tuberculosis.

Mycobacterium tuberculosis aerogenic rechallenge infections in B cell-deficient mice

OBJECTIVE

Use gene disrupted mice to examine the possible role of secretory antibody on resistance to re-exposure to pulmonary tuberculosis.

DESIGN

Mice deficient in B cells due to targeted gene disruption were infected by aerosol exposure with Mycobacterium tuberculosis. A further set were identically exposed then given isoniazid to clear the infection and establish a state of memory immunity.

RESULTS

Control of the aerosol infection and generation of gamma interferon proceeded in a similar manner in both naive and memory immune mice, regardless of B cell deficiency.

CONCLUSIONS

The absence of antibody responses did not affect the course of infection, thus confirming the classical literature that antibody plays no significant protective role.

Total body and regional bone mineral density in men: effect of age

Bone density is related to the risk of fracture, with a decrease in bone density resulting in an increased risk of fracture. The aims of this study were to characterize the relationship between bone mineral density (BMD) and age at different skeletal sites in men, and to determine whether the BMD pattern with age reflects the pattern of fracture in men. We studied 178 healthy Caucasian men, ages 20-79 years (approximately 30 per decade) from a general practitioner register. Spinal radiographs were obtained from men over 50 years of age and graded by a radiologist for spinal osteoarthritis by the method of Kellgren. BMD was measured by dual-energy X-ray absorptiometry at the anteroposterior (AP) lumbar spine, femoral neck, Ward's triangle, trochanter, ultradistal forearm and total body (providing estimates for the pelvis, head, arms, legs, trunk, ribs and spine). Severe osteoarthritis (grades 3 and 4) was associated with increased spine BMD, and therefore individuals with severe osteoarthritis were excluded from analysis of the spine. There was a decrease in height of vertebrae L2-4 in men between 20 and 79 years of age (4%), resulting in a decrease in projected area. The change in BMD in standard deviation units (T-score) between 20 and 79 years was calculated: there were significant decreases at the femoral neck (-1.6), Ward's triangle (-2.4), total body (-0.6), and its subregions the pelvis (-1.4), trunk (-0.8), ribs (-0.7) and legs (-0.7). There was no change in BMD with age at the AP lumbar spine, ultradistal forearm, or the total body subregion of the head. Similar results were found after adjusting for height and weight. Thus, there was only a small decrease in total body BMD across life, but a substantial decrease in BMD of the pelvis and proximal femur, sites rich in trabecular bone. These are the same sites associated with substantial increases in fracture incidence in men with aging.

Role of gamma delta T cells in immunopathology of pulmonary Mycobacterium avium infection in mice

Several studies have shown that gamma delta T cells influence granuloma development after infection with intracellular pathogens. The role of gamma delta T cells in controlling the influx of inflammatory cells into the lung after Mycobacterium avium infection was therefore examined with gene-disrupted mice (K/O). The mice were infected with either M. avium 724, a progressively replicating highly virulent strain of M. avium, or with M. avium 2-151 SmT, a virulent strain that induces a chronic infection. gamma delta-K/O mice infected with M. avium 2-151 SmT showed early enhanced bacterial growth within the lung compared to the wild-type mice, although granuloma formation was similar in both strains. gamma delta-K/O mice infected with M. avium 724 showed identical bacterial growth within the lung compared to the wild-type mice, but they developed more-compact lymphocytic granulomas and did not show the extensive neutrophil influx and widespread tissue necrosis seen in wild-type mice. These data support the hypothesis that isolates of M. avium that induce protective T-cell-specific immunity are largely unaffected by the absence of gammadelta T cells. Whereas with bacterial strains that induce poor protective immunity, the absence of gamma delta T cells led to significant reductions in both the influx of neutrophils and tissue damage within the lungs of infected mice.

Immunopathogenesis of Mycobacterium avium infection

One of the most obvious problems one perceives when working with Mycobacterium avium isolates is the vast array of phenotypes expressed with regard to colonial morphotype, serovar and particularly virulence. Thus whenever experimental data derived from different MAC isolates is compared the variety of this group of mycobacteria must always be considered. Another issue of concern is the extrapolation of in vitro data to the in vivo disease. We have reported, in the past, that survival in murine macrophage culture does not always correlate with survival in vivo (23). It is plausible therefore, that the pathways outlined in section 5.2 and figure 3 play a crucial role in the initiation of the innate immune response in general and that there are components of this response which are not expressed by IFN-gamma activated macrophages but which are necessary for bacterial control. In conclusion, we suggest that the initial control of MAC infection requires a healthy lung (or gut) architecture and that control by unactivated macrophages includes respiratory burst activity and also the sequestration of free iron away from the mycobacterial phagosome. Acquired immunity is important in controlling bacteria which have overcome the innate response and this control is mediated by cytokine activation of infected macrophages. Finally, we have described an animal model of infection in which uncontrolled bacterial growth occurs and in which lesions similar to those seen in AIDS patients develop.

Expression of memory immunity in the lung following re-exposure to Mycobacterium tuberculosis

OBJECTIVE

To examine the memory immunity expressed in the lung in response to a low-dose aerosol challenge.

DESIGN

Memory-immune C57BL/6 mice were generated by infection followed by drug treatment with isoniazid and rifabutin. Both memory-immune and naive mice were then rechallenged via both the aerosol and intravenous routes. The growth of bacteria in target organs, the expression of cytokines within these organs and the ability of T cells to recognize selected mycobacterial protein antigens were determined over time.

RESULTS

There was a finite delay before immunity was expressed in the lungs of the memory-immune mice. This was in contrast to the immediate control of bacterial growth seen in the liver of intravenously challenged mice. In both cases, the expression of interferon-gamma (IFN-gamma) mRNA in the target organ correlated with the control of bacterial growth. Memory immunity in the spleen and lung differed: whereas splenic T cells strongly recognized the major Ag85 protein, the 45 kDa protein, and a synthetic peptide representing the ESAT molecule, only the Ag85 molecule was recognized by T cells harvested from thoracic lymph nodes after pulmonary rechallenge.

CONCLUSIONS

Immunity, as mediated by IFN-gamma, is expressed more slowly following an aerosol rechallenge and appears to be restricted in terms of antigen specificity. Moreover, very strong levels of memory immunity can prevent progressive disease in the lungs, but cannot prevent the establishment of secondary infection.

Disruption of the cellular inflammatory response to Listeria monocytogenes infection in mice with disruptions in targeted genes

The results of this study to dissect the nature of the acquired immune response to infection with Listeria monocytogenes in mice with targetted gene disruptions show that successful resolution of disease requires the essential presence of alphabeta T cells and the capacity to elaborate gamma interferon. In the absence of either of these entities, mice experience increasingly severe hepatitis and tissue necrosis and die within a few days. The data from this study support the hypothesis that the protective process is the efficient replacement of neutrophils in lesions by longer-lived mononuclear phagocytes; alphabeta-T-cell-knockout mice died from progressive infection before neutrophil replacement could occur, whereas in gammadelta-T-cell-knockout mice this replacement process in the liver has previously been shown to be much slower. In the present study we attribute this delay to reduced production of the macrophage-attracting chemokine MCP-1 in the gammadelta-T-cell-knockout animals. These data further support the hypothesis that gammadelta T cells are important in controlling the inflammatory process rather than being essential to the expression of protection.

Adequate expression of protective immunity in the absence of granuloma formation in Mycobacterium tuberculosis-infected mice with a disruption in the intracellular adhesion molecule 1 gene

It remains unknown whether the expression of cell-mediated protective immunity and the capacity to mount a delayed-type hypersensitivity (DTH) reaction in tuberculosis infection represent two manifestations of a basic response or are dissociable events. In this study, we present data in favor of the latter hypothesis, by showing that tuberculosis infection in the lungs of mice possessing only a truncated form of intracellular adhesion molecule 1 due to gene disruption was still adequately controlled by the expression of protective immunity in the absence of any sustained influx of macrophages and the lack of formation of appreciable granulomas. These animals also had no detectable DTH response to mycobacterial proteins in the footpad assay, indicating that the accumulation of blood-borne macrophages at sites of mycobacterial infection or antigen deposition is not essential to control of the infection. These data support the hypothesis that the DTH component of the cellular response is not protective but contributes by walling off the sites of infection to prevent dissemination and reactivation disease.

Interleukin 12 (IL-12) is crucial to the development of protective immunity in mice intravenously infected with mycobacterium tuberculosis

Immunity to Mycobacterium tuberculosis infection is associated with the emergence of protective CD4 T cells that secrete cytokines, resulting in activation of macrophages and the recruitment of monocytes to initiate granuloma formation. The cytokine-mediating macrophage activation is interferon-gamma (IFN-gamma), which is largely dependent on interleukin-12 (IL-12) for its induction. To address the role of IL-12 in immunity to tuberculosis, IL-12 p40(-/-) mice were infected with M. tuberculosis and their capacity to control bacterial growth and other characteristics of their immune response were determined. The IL-12 p40(-/-) mice were unable to control bacterial growth and this appeared to be linked to the absence of both innate and acquired sources of IFN-gamma. T cell activation as measured by delayed type hypersensitivity and lymphocyte accumulation at the site of infection were both markedly reduced in the IL-12 p40(-/-) mice. Therefore, IL-12 is essential to the generation of a protective immune response to M. tuberculosis, with its main functions being the induction of the expression of IFN-gamma and the activation of antigen-specific lymphocytes capable of creating a protective granuloma.

The course of Mycobacterium tuberculosis infection in the lungs of mice lacking expression of either perforin- or granzyme-mediated cytolytic mechanisms

CD8 T cells have been shown to be protective against Mycobacterium tuberculosis infections in the mouse. These cells have been shown to be cytolytic toward M. tuberculosis-infected cells and have also been shown to release the protective cytokine gamma interferon in response to mycobacterial antigen. It has therefore been unclear how these cells mediate their protective response. To dissect this problem, we compared the courses of M. tuberculosis infections in control, perforin gene-knockout, and granzyme gene-knockout mice exposed by the realistic pulmonary route. The inability to express either of these molecules limits the expression of the major lytic pathway but does not appear to influence the course of the infection or result in any discernible histologic differences. These data seem to rule against a lytic role for CD8 T cells in the lungs and hence tend to suggest instead that another type of mechanism, such as cytokine secretion by these cells, is their primary mode of action.

Evidence for a reduced chemokine response in the lungs of beige mice infected with Mycobacterium avium

The basis of the increased susceptibility of beige mice to Mycobacterium avium infections is still not clearly understood. In this study we examined the growth of three virulent strains of M. avium in beige mice and normal C57BL/6 controls. Depletion of natural killer (NK) cells by administration of anti-asialo GM1 antisera did not affect the growth of M. avium in any of the groups of animals. Similarly, interferon-gamma (IFN-gamma) gene-disrupted mice were more susceptible to infection than control mice but the growth of M. avium was not further affected by NK-cell depletion. In terms of effector immunity, beige mice showed enhanced expression of IFN-gamma and tumour necrosis factor-alpha (TNF-alpha) when compared with wild-type C57BL/6 mice. In agreement with these results; I-A and interferon-inducible protein (IP-10) expression was also higher in beige mice than in wild-type animals, as was expression of the chemokines macrophage inflammatory protein-2 (MIP-2) and macrophage chemotactic protein (MCP-1) during latter stages of the infection. However, over the first few weeks of the infection, when the susceptibility of the beige mouse lung first becomes evident, MIP-1 beta and MIP-2 chemokine expression in the lungs was lower in beige mice than in wild-type animals. These data indicate, therefore, that the increased susceptibility of beige mice to M. avium infection in the lung is not due to lack of NK-cell activity, nor can it be explained in terms of the effector cytokine response. Instead, the lower early expression of the neutrophil chemoattractants MIP-1 beta and MIP-2 in the lungs of beige mice tends to suggest that the enhanced susceptibility of these mice to M. avium infection may be due in part to defective recruitment of neutrophils or other cells responsive to these specific chemokines.

An anti-inflammatory role for gamma delta T lymphocytes in acquired immunity to Mycobacterium tuberculosis

Although a role for gammadelta receptor-bearing T cells in the acquired immune response to infection with Mycobacterium tuberculosis is suggested by several lines of evidence, the only data indicating a possible role in specific protective immunity have been provided by very high dose i.v. infection models. In the current study, more modest low dose inocula delivered by the aerosol route grew identically in wild-type controls and in mutant mice in which the Cdelta gene of the gammadelta TCR has been disrupted by homologous recombination. This situation did not change if the inoculum size was increased or if an aerosol challenge with an M. tuberculosis strain of higher virulence was given. However, while the control and containment of these infections was similar, the mutant mice exhibited a substantial pyogenic form of the granulomatous response compared with the lymphocytic response seen in control animals, a finding that may well explain mortality in the former group if high i.v. doses are given. These data indicate that gammadelta T cells do not directly contribute to protection against tuberculosis or that they do so only when bacterial loads are very high. Instead, the data suggest that gammadelta T cells perhaps play an important role by influencing local cellular traffic, promoting the influx of lymphocytes and monocytes, and limiting the access of inflammatory cells that do not contribute to protection but may cause tissue damage.

An anti-inflammatory role for gamma delta T lymphocytes in acquired immunity to Mycobacterium tuberculosis

Although a role for gammadelta receptor-bearing T cells in the acquired immune response to infection with Mycobacterium tuberculosis is suggested by several lines of evidence, the only data indicating a possible role in specific protective immunity have been provided by very high dose i.v. infection models. In the current study, more modest low dose inocula delivered by the aerosol route grew identically in wild-type controls and in mutant mice in which the Cdelta gene of the gammadelta TCR has been disrupted by homologous recombination. This situation did not change if the inoculum size was increased or if an aerosol challenge with an M. tuberculosis strain of higher virulence was given. However, while the control and containment of these infections was similar, the mutant mice exhibited a substantial pyogenic form of the granulomatous response compared with the lymphocytic response seen in control animals, a finding that may well explain mortality in the former group if high i.v. doses are given. These data indicate that gammadelta T cells do not directly contribute to protection against tuberculosis or that they do so only when bacterial loads are very high. Instead, the data suggest that gammadelta T cells perhaps play an important role by influencing local cellular traffic, promoting the influx of lymphocytes and monocytes, and limiting the access of inflammatory cells that do not contribute to protection but may cause tissue damage.

Antimycobacterial action of thiolactomycin: an inhibitor of fatty acid and mycolic acid synthesis

Thiolactomycin (TLM) possesses in vivo antimycobacterial activity against the saprophytic strain Mycobacterium smegmatis mc2155 and the virulent strain M. tuberculosis Erdman, resulting in complete inhibition of growth on solid media at 75 and 25 micrograms/ml, respectively. Use of an in vitro murine macrophage model also demonstrated the killing of viable intracellular M. tuberculosis in a dose-dependent manner. Through the use of in vivo [1,2-14C]acetate labeling of M. smegmatis, TLM was shown to inhibit the synthesis of both fatty acids and mycolic acids. However, synthesis of the shorter-chain alpha'-mycolates of M. smegmatis was not inhibited by TLM, whereas synthesis of the characteristic longer-chain alpha-mycolates and epoxymycolates was almost completely inhibited at 75 micrograms/ml. The use of M. smegmatis cell extracts demonstrated that TLM specifically inhibited the mycobacterial acyl carrier protein-dependent type II fatty acid synthase (FAS-II) but not the multifunctional type I fatty acid synthase (FAS-I). In addition, selective inhibition of long-chain mycolate synthesis by TLM was demonstrated in a dose-response manner in purified, cell wall-containing extracts of M. smegmatis cells. The in vivo and in vitro data and knowledge of the mechanism of TLM resistance in Escherichia coli suggest that two distinct TLM targets exist in mycobacteria, the beta-ketoacyl-acyl carrier protein synthases involved in FAS-II and the elongation steps leading to the synthesis of the alpha-mycolates and oxygenated mycolates. The efficacy of TLM against M. smegmatis and M. tuberculosis provides the prospects of identifying fatty acid and mycolic acid biosynthetic genes and revealing a novel range of chemotherapeutic agents directed against M. tuberculosis.

Chemokine response in mice infected with Mycobacterium tuberculosis

We show here that infection of murine macrophages with various strains of Mycobacterium tuberculosis induces the rapid in vitro expression of genes encoding chemokines macrophage inflammatory protein 1 alpha and macrophage inflammatory protein 2, which recruit neutrophils to sites of infection, and macrophage-recruiting chemokines 10-kDa, interferon-inducible protein (IP-10) and macrophage chemotactic protein 1. Three strains of M. tuberculosis, Erdman and the clinical isolates CSU 22 and CSU 46, induced similar levels of secretion of macrophage chemotactic protein 1 from infected macrophage monolayers; however, the Erdman strain failed to induce levels of secretion of tumor necrosis factor alpha similar to those induced by either CSU 22 or CSU 46. Using a low-dose aerosol infection model, we also found that while the Erdman strain induced negligible increases in chemokine mRNA levels in the lungs, infection with either CSU 22 or CSU 46 resulted in greater levels of mRNA production for all four chemokines tested. The growth of these strains in the lungs was, however, equally well contained by acquired host immunity. These data allow us to hypothesize that the chemokine response in the lungs probably does not control the protective granulomatous response and that perhaps other T-cell- or macrophage-associated cytokines such as tumor necrosis factor alpha or interleukin 12 may be involved in this process.

Old mice are able to control low-dose aerogenic infections with Mycobacterium tuberculosis

Previous work in this laboratory has led to the development of the hypothesis that the increased susceptibility of old mice to tuberculosis infection reflects a limited ability by immune CD4 mediator cells to accumulate at sites of bacterial implantation. To test this hypothesis with very low dose infections, the present study documented the course of a low-dose aerogenic infection with virulent Mycobacterium tuberculosis Erdman against time in the target organs of young (3-month-old) and old (24-month-old) B6D2F1 hybrid mice. The results of the study indicated that the infection was controlled by the two groups of mice at similar rates, although the bacterial load in the old mice was eventually somewhat higher. Despite these similarities, some subtle differences between the young and old mice were also evident and included evidence of increased hematogenous spread of the infection from the lungs to other organs in the old mice. Interestingly, very poor expression of the cytokine interleukin-12 was observed in the lungs of infected old mice, leading to the hypothesis that the poor CD4 response in such animals could be partially attributed to the lack of this Th1-type, CD4 T-cell-enhancing cytokine. In this regard, treatment of old mice with exogenous interleukin-12 increased resistance and promoted gamma interferon secretion by CD4 T cells from these mice, although the effects were generally modest. These data suggest that old mice possess CD4-independent compensatory mechanisms by which to deal with low-dose pulmonary tuberculosis infections, although such mechanisms are less efficient than those seen in young animals.

The protective immune response to Mycobacterium tuberculosis

Recent advances have characterized the protective immune response against Mycobacterium tuberculosis. These include identification of the phenotype of some protective cells, the antigens to which these cells respond and the cytokines produced in response to infection which modulate disease. Progress has also been made in inducing this response by vaccination.

An empirical study of defense mechanisms in panic disorder

Psychodynamic factors have rarely been systematically studied in panic disorder, despite indications that these factors may be important in the understanding and treatment of panic. This is a report of a study using the Defense Mechanism Rating Scale to test the hypothesis that patients with panic disorder utilize particular defense mechanisms: reaction formation, undoing, and displacement. The use of defense mechanisms in 22 patients with primary panic disorder was compared with that of 22 patients with primary dysthymic disorder, based on Defense Mechanism Rating Scale ratings of psychodynamic interviews of these patients. Panic subjects scored significantly higher than dysthymics on the defenses of reaction formation and undoing, but not on the defense of displacement. The defense mechanisms found are consistent with a proposed psychodynamic formulation for panic disorder that emphasizes the panic patient's difficulty in tolerating angry feelings toward significant others. Knowledge of these defense mechanisms can be useful for various treatment approaches in panic disorder.

The role of interleukin-12 in acquired immunity to Mycobacterium tuberculosis infection

The early phase of acquired cellular immunity to Mycobacterium tuberculosis infection is mediated by the emergence of protective CD4 T lymphocytes that secrete cytokines including interferon-gamma (IFN-gamma), a molecule which is pivotal in the expression of resistance to tuberculosis. Recent evidence demonstrates that infection with M. tuberculosis induces peripheral blood mononuclear cells to release the cytokine interleukin-12 (IL-12), a molecule that promotes the emergence of T-helper type-1 (Th1), IFN-gamma-producing T cells. We demonstrate here that IL-12 mRNA expression was induced by M. tuberculosis infection both in vivo and in vitro and that exogenous administration of IL-12 to mice transiently resulted in increased resistance to the infection. IL-12 also increased the production of IFN-gamma by both splenocytes derived from infected animals treated in vivo and by antigen-stimulated CD4 cells from untreated infected animals, with maximal effects at times associated with the expansion of antigen-specific CD4 T cells in vivo. In the absence of a T-cell response, as seen in SCID mice or nude mice, IL-12 only slightly augmented the moderate bacteriostatic capacity of these immunocompromised mice. Neutralization of IL-12 by specific monoclonal antibodies resulted in a reduction in granuloma integrity and slowing of the capacity of the animal to control bacterial growth.

The effect of liposomally conjugated methotrexate upon mediator release from human peripheral blood monocytes

The ability of methotrexate (MTX) and a liposomal preparation containing a lipophilic conjugate of methotrexate (MTX-LIPO) to modulate pro-inflammatory mediator release from lipopolysaccharide-stimulated human peripheral blood monocytes was investigated. At non-toxic concentrations MTX-LIPO (10 micrograms MTX per 250 micrograms lipid) was a potent inhibitor of both IL-1 beta and TNF release resulting in 70.07 +/- 2.3% and 59.19 +/- 2.36% (mean +/- S.E.M.) inhibition, respectively, whereas empty liposomes (E-LIPO; 250 micrograms lipid/well) of the same lipid composition and free MTX (up to 100 micrograms/well) had no effect on either mediator.

Formulations to the patient: explicit and implicit

Many of our formulations to the patient are conveyed through the day-to-day unremarkable actions, verbal and nonverbal, occurring between analyst and patient as the analyst attempts to understand his patient within the analytic setting. The analyst's confidence, even intensity, concerning the value of analysis is significant in enabling him to communicate successfully with his patient. Unlike what may have been the case in the past, this analytic fervour is not in the service of a single theory or an attempt to prove an analytic proposition, but is aimed at deepening introspective curiosity and opening avenues of communication. Within our characterologic and procedural limits, we use ourselves in a large variety of ways in an attempt to further the analytic process. This use of ourselves, conveyed to the patient in innumerable interactions, becomes a central analytic fact that fosters the patient's participation in his analysis. Clinical vignettes are provided to illustrate these propositions.

Expression of complement regulatory molecules and other surface markers on neutrophils from synovial fluid and blood of patients with rheumatoid arthritis

In an effort to elucidate the activation status of neutrophils (PMN) in inflammatory joint disease the expression of relevant cell surface proteins was examined using immunofluorescence and flow cytometry. Paired samples of SF and peripheral blood were obtained from 18 patients with RA and PMN purified using methods designed to minimize activation in vitro. We then used flow cytometry to measure expression of the four membrane complement regulatory molecules, decay accelerating factor (DAF; CD55), complement receptor 1 (CR1; CD35), membrane cofactor protein (MCP; CD46) and CD59; two adhesion molecules of the integrin family LFA1 (alpha chain, CD11a), complement receptor 3 (CR3; alpha chain, CD11b), and their common beta chain (CD18); the major receptor for immune complexes Fc gamma RIII (CD16), and the leucocyte common antigen tyrosine phosphatase (L-CA; CD45). Expression of these molecules was also measured on peripheral blood PMN from 18 age- and sex-matched normal controls. In RA, SF PMN expressed significantly higher levels of the complement regulators CD55 and CD35, the adhesion molecule CR3 (CD11b/CD18) and of CD45 but significantly lower levels of CD46 and CD11a in comparison with blood PMN from the same patient. Expression of CD59 and CD16 did not differ between the two groups. These changes may increase adhesiveness and complement resistance of PMN in SF compared with blood. PMN from RA expressed significantly less of all the complement C3 convertase regulators (CD55, CD46, CD35), all the adhesion molecules (CD11a, CD11b, CD18) and the phosphatase CD45 than did blood PMN from age and sex-matched control individuals.

Sacroiliac joint sepsis

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Altered Ca2+ signalling in human neutrophils from inflammatory sites

OBJECTIVES

To determine whether the intracellular store release of Ca2+ in neutrophils from patients with rheumatoid arthritis, other joint disease and active leg ulceration was different from normal neutrophils.

METHODS

The release into the cytosol of Ca2+ from stores within individual neutrophils was determined using ratiometric imaging of fura2. The size of the elevated Ca2+ 'cloud' and its concentration were quantified in neutrophils from the circulation of patients with rheumatoid arthritis, other joint diseases, and leg ulcers and from the joints of those with joint disease.

RESULTS

In neutrophils isolated from both the synovial fluid of patients with rheumatoid arthritis and other joint conditions, and also arising from leg ulcers, the amount of the cell cytosol occupied by elevated Ca2+ was significantly increased compared with neutrophils from healthy subjects; for neutrophils from rheumatoid, non-rheumatoid joints and leg ulcers p values were 0.0006, < 0.0001, 0.016 respectively (Student's t test). There was also a significant increase in Ca2+ release from circulating neutrophils from patients with rheumatoid arthritis (p = 0.09), but not in circulating neutrophils from patients with leg ulcers or non-rheumatoid joint conditions.

CONCLUSIONS

It is proposed that the increased release of free Ca2+ into the cytosol of neutrophil at inflammatory sites results in increased oxidase activation.

T-cell responses to infected autologous monocytes in patients with cutaneous and mucocutaneous leishmaniasis

Although there is strong evidence that the control and resolution of human leishmanial infections depend primarily on activation of parasite-infected macrophages mediated by lymphokines derived from T cells, less is known about the nature of the responding cell type(s) which is protective or the antigen(s) (Ag[s]) that elicits these cells to respond. Studies using preparations of whole soluble Ag ("dead Ag") show that patients respond to a wide range of leishmanial Ags. The objective of the present study was to characterize the response of T cells from patients with healing or healed cutaneous or mucosal infections to Ag expressed by or derived from actively infected autologous monocytes ("live Ag"). Unfractionated T cells proliferated and produced gamma interferon in response to both live and dead Ags. Depletion of CD4+ T cells resulted in the loss of proliferative and gamma interferon responses to both live and dead Ags. The effect of CD8 depletion, although variable and not limited to the cells stimulated by infected monocytes, was clear for some patients. Expansion of T cells specific for live Ags by using amastigote-infected cells followed by restimulation with fast-protein liquid chromatography-fractionated soluble Ags revealed that a diversity of Ags are associated with infected monocytes. There may, however, be quantitative differences in the expression of certain Ags since prestimulation with live Ag induced higher responses to restimulation in mucocutaneous leishmaniasis patients than in localized cutaneous leishmaniasis patients. Prestimulation with dead Ag induced similar secondary responses in both patient groups.