The role of TGF beta in the pathogenesis of human tuberculosis

Endocrine and cytokine responses in humans with pulmonary tuberculosis

Endocrine responses during chronic infections such as lung tuberculosis are poorly characterized. Hormonal changes are likely to occur since some of the cytokines produced during this disease could affect endocrine mechanisms that, in turn, influence the course of infectious/inflammatory processes. A main purpose of this work was to study endocrine responses involving pituitary, adrenal, gonadal, and thyroid hormones in parallel to IFN-gamma, IL-10, and IL-6 levels in tuberculosis patients with different degree of pulmonary involvement. We have also studied whether products derived from peripheral immune cells obtained from the patients can affect the in vitro production of adrenal steroids. The population studied comprised HIV-negative newly diagnosed, untreated male patients with mild, moderate, and advanced lung tuberculosis, and matched, healthy controls. IFN-gamma, IL-10, and IL-6 levels were elevated in patients with tuberculosis. Dehydroepiandrosterone and testosterone levels were profoundly decreased and growth hormone levels were markedly elevated in patients, in parallel to modest increases in cortisol, estradiol, prolactin, and thyroid hormone concentrations. Supernatants of peripheral blood mononuclear cells obtained from the patients and stimulated in vitro with Mycobacterium tuberculosis antigens significantly inhibited dehydroepiandrosterone secretion by the human adrenal cell line NCI-H295-R. These results support the hypothesis that at least some of the endocrine changes observed in the patients may be mediated by endogenous cytokines. The endocrine profile of tuberculosis patients would favor a reduction of protective cell-mediated immunity and an exacerbation of inflammation leading to perpetuation of the lung injury and to the hypercatabolic condition that characterizes this disease.

Changes in the levels of interferon-gamma and transforming growth factor-beta influence bronchial stenosis during the treatment of endobronchial tuberculosis

BACKGROUND

Endobronchial tuberculosis (EBTB) has been shown to frequently complicate bronchial stenosis, a condition which can induce dyspnea as a result of airway obstruction, and is also frequently misdiagnosed as either bronchial asthma or lung cancer.

OBJECTIVES

This study attempted to determine whether there was a correlation between interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta) levels in the serum and bronchial washing fluid (BWF), and the results of the treatment of EBTB patients.

METHODS

Thirty patients, all of whom were diagnosed as EBTB, were enrolled, as were 10 healthy control subjects. IFN-gamma and TGF-beta levels were measured by the ELISA method in the serum and BWF of these 30 EBTB patients before and after treatment. The EBTB patients were divided into two groups: those who exhibited bronchial stenosis after treatment and those who did not. Chest computed tomography (CT) and pulmonary function test (PFT) were performed in 16 and 25 patients, respectively, at initial bronchoscopy.

RESULTS

IFN-gamma and TGF-beta levels in the BWF of the EBTB patients were elevated compared to the controls (p < 0.05). After 2 months of treatment, 13 of the 30 EBTB patients exhibited bronchial fibrostenosis and the other 17 cases had recovered without sequelae. In the bronchial stenosis group, the initial serum TGF-beta levels were lower than in the patients without bronchial stenosis (p < 0.05). Moreover, the levels of serum TGF-beta after treatment were shown to have decreased more than in the patients without bronchial stenosis (p < 0.05). On chest CT findings of 16 EBTB patients, bronchial narrowing was suspected except in 2 cases (1 edematous-hyperemic type, 1 actively caseating type of segmental bronchus). The common features of PFT in EBTB at the initial diagnosis were a restrictive pattern and normal ventilatory function.

CONCLUSIONS

Elevated IFN-gamma and TGF-beta levels in the BWF of the EBTB patients may be related to EBTB pathogenesis. Lowered initial serum TGF-beta levels as well as the observed changes in the levels of TGF-beta in the serum after treatment have been implicated in bronchial fibrostenosis during the course of the disease.

A combination of a transforming growth factor-beta antagonist and an inhibitor of cyclooxygenase is an effective treatment for murine pulmonary tuberculosis

Transforming growth factor-beta (TGF-beta) and prostaglandins (PG) regulate the cell-mediated immune response, so it has been proposed that they affect the progression of pulmonary tuberculosis. Here we report that the administration of soluble betaglycan, a potent TGF-beta antagonist, and niflumic acid, a PG synthesis inhibitor, during the chronic phase of experimental murine tuberculosis enhanced Th1 and decreased Th2 cytokines, increased the expression of iNOS and reduced pulmonary inflammation, fibrosis and bacillary load. This immunotherapeutic approach resulted in significant control of the disease comparable to that achieved by anti-microbial treatment alone. Importantly, the combination of immunotherapy and anti-microbials resulted in an accelerated clearance of bacilli from the lung. These results confirm that TGF-beta and PG have a central pathophysiological role in the progression of pulmonary tuberculosis in the mouse and suggest that the addition of immunotherapy to conventional anti-microbial drugs might result in improved treatment of the disease.

Immunohistochemical markers augment evaluation of vaccine efficacy and disease severity in bacillus Calmette–Guerin (BCG) vaccinated cattle challenged with Mycobacterium bovis

Development of necrotic granulomas in response to Mycobacterium bovis infection in cattle is pathognomonic for bovine tuberculosis. Previously our laboratory reported on M. bovis granuloma classification by stage of lesion advancement within bovine lymph nodes and developed immunohistochemical markers to further characterize these granulomas. In this study of bovine lymph node granulomas we applied this classification system to assess the dynamics of vaccination challenge. Lymph nodes collected from cattle vaccinated with M. bovis bacillus Calmette-Guerin (BCG) and subsequently challenged with virulent M. bovis were compared to lymph nodes from unvaccinated, challenged cattle. Expression of interferon-gamma (IFN-gamma), transforming growth factor-beta (TGF-beta), type I procollagen and cell marker identification of T cells, B cells, macrophages and WC1(+)gammadelta TCR+ cells were assessed. Granulomas formed in vaccinated cattle were greatly reduced in number, area, degree of necrosis and peripheral fibrosis and contained fewer Langhans' giant cells, acid fast bacilli, WC1(+)gammadelta TCR+ cells and less TGF-beta expression in comparison to controls. B cells clustered intensely along the outer granuloma margins within vaccinated calves, with significantly more IFN-gamma producing cells identified in the medullary regions of lymph nodes from BCG-vaccinated animals compared to unvaccinated controls. This may be indicative of immune activation and surveillance in regions not directly associated with ongoing disease. Lymph node evaluation using light microscopy and immunohistochemical markers is useful to assess the immune response and discriminate granulomas to determine vaccine efficacy and disease severity.

The local immune response in ulcerative lesions of Buruli disease

Buruli disease (BU) is a progressive necrotic and ulcerative disease of the skin and subcutaneous tissue caused by Mycobacterium ulcerans. BU is considered the third most common mycobacterial disease after tuberculosis and leprosy. Three clinical stages of the cutaneous lesions have been described in BU: pre-ulcerative, ulcerative and healed lesions. In this study we used immunohistochemistry and automated morphometry to determine the percentage of macrophages and of CD4/CD8 lymphocytes and their expression of interferon (IFN)-gamma, interleukin (IL)-10, tumour necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta. Expression of these cytokines was correlated with the inflammatory response evaluated by histopathology. All the studied BU ulcerative cases showed extensive necrosis and chronic inflammation. The most important feature was the presence or absence of granulomas co-existing with a mixed pro-inflammatory/anti-inflammatory cytokine balance. When granulomas were present significantly higher expression of IFN-gamma was seen, whereas in ulcerative lesions without granulomas there was increased expression of IL-10 and significantly higher bacillary counts. These features correlated with the chronicity of the lesions; longer-lasting lesions showed granulomas. Thus, granulomas were absent from relatively early ulcerative lesions, which contained more bacilli and little IFN-gamma, suggesting that at this stage of the disease strong suppression of the protective cellular immune response facilitates proliferation of bacilli.

Changes in serum cytokine levels in active tuberculosis with treatment

It has been reported that IFN-γ, TNF-α, and IL-12 stimulate, and that IL-10, TGF-β, and IL-4 suppress the protective immune response against tuberculosis. We aim to evaluate changes in the serum levels of pro and antiinflammatory cytokines in active pulmonary tuberculosis (APTB) and the possible effects of treatment on these changes. Serum IL-12p40, IL-4, IL-10, TNF-α, IFN-γ, and TGF-β1 levels were determined in 20 APTB cases (group 1) before and 2, 4, and 6 months after therapy. The same parameters were also determined in 9 inactive pulmonary tuberculosis (IPTB) cases (group 2) and 9 healthy controls (HC, group 3). Before treatment, the mean serum IFN-γ, TNF-α, and IL-10 levels in group 1 were statistically higher than those in group 2 (P = .001, P = .024, P = .016, resp) or group 3 (P = .003, P = .002, P = .011, resp). The levels in group 1 decreased significantly after treatment (P = .001 for IFN-γ, P = .004 for TNF-α, P = .000 for IL-10). The serum levels of IL-12p40 were significantly higher in group 1 than in group 3 (P = .012) and decreased insignificantly after treatment. There was no difference in serum IL-4 and TGF-β1 levels among the groups (P > .05). Because the serum IL-12p40, IL-10, TNF-α, and IFN-γ levels were high in APTB, we believe that these cytokines have important roles in the immune response to Mycobacterium tuberculosis (M tuberculosis). These parameters could be used in follow-up as indicators of the success of APTB therapy.

Immune systems in developed and developing countries; implications for the design of vaccines that will work where BCG does not

New vaccine candidates for tuberculosis are beginning to enter clinical trials. In this review we discuss issues surrounding the design of these candidates, and the way they were screened in animal models. First, screening vaccines for their ability to attenuate inevitably fatal tuberculosis in immunologically naïve mice might be leading to the selection of inappropriate candidates. We need to screen vaccines for their ability to stop the development of progressive disease, since this is what they must achieve in man. A solution to this problem is proposed. Secondly, we point out that some mouse models of tuberculosis in laboratories in developing countries, where exposure to environmental mycobacteria is large, mimic neglected aspects of human disease more closely than do low-dose infections in hyper-susceptible immunologically naïve mice in the USA or Europe. We need to think more about geographical differences in immunological experience, and these mouse models can help us. Thirdly, we conclude that in developing countries where BCG fails this is not because there is too little Th1 response, but rather because the Th1 response is rendered ineffective and immunopathological by other subversive mechanisms, including IL-4 responses and inappropriate regulatory T cell function. Therefore, we suggest that vaccines that will work in those countries might need to have immunoregulatory properties that can switch off pre-existing subversive mechanisms, and block their development in the future. The development of such vaccines, that might work where BCG does not, will require a greater understanding of the roles of the many types of regulatory T cell in tuberculosis.

A calcium-based theory of carcinogenesis

Most human cancers are initiated by chronic injuries that repeatedly kill cells and must, therefore, repeatedly raise cell calcium within nearby survivors. They may also raise calcium in distant cells via calcium waves. Here it is argued that these calcium increases initiate oncogenesis by breaking gap junctions and thus disorganizing tissues and by activating proto-oncogenes. It is also argued that these calcium increases become self-perpetuating in part through the development of an ability of cells to divide in reduced extracellular calcium, i.e., habituation to reduced extracellular calcium. I propose to test these calcium-based theories by using aequorinated mice.

Kinetics of T lymphocyte responses to persistent antigens

Long term sequential study of immune responses in the same individuals is difficult from the time commitment required and the problem of maintaining enough subjects to provide for comparative analysis. We closely studied one hundred women with silicone mammary devices through cross sectional analysis up to 26 years post implantation and a similar sample of women to 6 years post explantation. The T cell index, calculated from tritiated thymidine incorporation during lymphoblast transformation, rose to a post implant peak at 10.5-12.0 years, falling progressively over the next 14.0-15.5 years to values indicative of probable immune quiescence. Post explantation, the index rose over the first 3 years and then sharply declined to within the range for unexposed controls. The shape of these time curves contains considerable information referent cell dynamics for both stimulatory and inhibitory factors and for demonstrating net group effects, appropriate to analysis in the cross sectional perspective. When a subset of four women was studied frequently and sequentially up to 8 years, an internal oscillatory pattern emerged, focusing attention on both the stimulatory and the inhibitory aspects of long term clonal expansion. IL-2 has stimulatory and inhibitory properties at different levels of production and is considered a prime candidate as the essential cytokine. The equations have details, however, which require exploration beyond any such provisional conclusion. The analytic process was aided by normalization of oscillatory data to eliminate subject variability and by Pareto optimization to assess the trend shown by normalization. Pareto analysis revealed two minimally coordinated oscillations, one over time and the other along net clonal expansion or decline of the siloxane specific T lymphocyte clone. The segments of the time related oscillation greatly exceeded the reaction times of cytokines currently known to be active in T cell regulation. Although the ultimate controlling factor(s) may be cytokine or chemokine combinations, the data are compatible with some more basic regulatory factor(s) of cell integrity, including limits on the number of cell divisions which can be sustained in long term immunopathic lesions, among other processes.

TNF-alpha, TGF-beta and NO relationship in sera from tuberculosis (TB) patients of different severity

Tuberculosis (TB) is the main cause of death by infection diseases worldwide. Considering that NO, TNF-alpha and TGF-beta participate a great deal in TB immunopathogenesis, we wished to analyse whether these mediators showed some relationship with the degree of pulmonary affectation. The sample comprised 29 TB (HIV-), inpatients with mild-moderate (n = 10) or advanced (n = 19) newly-diagnosed disease, together with 12 healthy controls HCo. Serum nitrite was assessed by reducing nitrate to nitrite, and further measured by the Griess reaction. Levels of TNF-alpha and TGF-beta were determined by ELISA (R&D Systems). Serum levels of TNF-alpha were significantly higher in the advanced TB cases if compared with HCo, (p < 0.05 ) and from values of Mild-Moderate TB patients (p < 0.05). Serum levels of TGF-beta from advanced TB patients have increased values if compared with Hco (p < 0.005) and Mild-Moderate patients (p < 0.05). These values were also significantly different from Mild-Moderate cases + HCo (p = 0.01) Advanced TB patients had significantly reduced nitrite levels compared with those of Mild-Moderate patients and HCo (p < 0.002). Taken as a whole NO-derived metabolites in TB patients (M-M and Advanced cases) remained lower than values in HCo (p = 0.005) A negative correlation was found when comparing the two cytokines with nitrites(r = -0.44 ).TGF-beta and TNF-alpha were positively correlated (r = 0.44, p < 0.01), 0.44, p < 0.01. In synthesis, the inverse correlation found between both cytokines concentrations and NO levels in TB patients may be viewed as a consequence of a more predominant TGF-beta effect.

Cortisol and dehydroepiandrosterone affect the response of peripheral blood mononuclear cells to mycobacterial antigens during tuberculosis

The effect of cortisol and/or dehydroepiandrosterone (DHEA) on the immune response to antigens obtained from Mycobacterium tuberculosis was studied in vitro by using peripheral blood mononuclear cells obtained from patients at various stages of lung tuberculosis (TB) and from healthy control people (HCo). The results obtained show for the first time that addition of cortisol within concentrations of physiological range can inhibit the mycobacterial antigen-driven proliferation of cells from HCo and TB patients and the production of interferon-gamma (IFN-gamma), indicating that endogenous levels of cortisol may contribute to the decreased lymphoid cell response to mycobacterium antigens observed in TB patients. DHEA did not affect lymphoid cell proliferation, IFN-gamma production and the cortisol-mediated inhibitory effects. Interestingly, we found that DHEA, but not cortisol, suppressed the in vitro transforming growth factor-beta production by lymphoid cells from TB patients with an advanced disease, which is indicative of a selective direct effect of this hormone.

Effects of gamma interferon, interleukin-10, and transforming growth factor beta on the survival of Mycobacterium avium subsp. paratuberculosis in monocyte-derived macrophages from naturally infected cattle

Gamma interferon (IFN-gamma) plays a significant role in the control of mycobacterial infections, including Mycobacterium avium subsp. paratuberculosis. However, the contribution of other immunoregulatory cytokines, such as interleukin-10 (IL-10) and transforming growth factor beta (TGF-beta), in Johne's disease has not been investigated as yet. In this study, we examined the effects of in vivo and in vitro infection with M. avium subsp. paratuberculosis on the production of IFN-gamma, IL-10, and TGF-beta by peripheral blood mononuclear cells (PBMC). We also examined the effects of exogenous IFN-gamma, IL-10, and TGF-beta on M. avium subsp. paratuberculosis survival in the cell cultures. PBMC obtained from naturally infected cows, regardless of their disease status, specifically upregulated IL-10 and TGF-beta in culture supernatants in response to stimulation with live M. avium subsp. paratuberculosis. Nonstimulated PBMC recovered from subclinically infected animals secreted the lowest levels of TGF-beta, but after stimulation with live M. avium subsp. paratuberculosis, TGF-beta levels in the culture supernatants increased to levels similar to that produced by PBMC from healthy animals. The numbers of viable M. avium subsp. paratuberculosis recovered from cultures from naturally infected animals were higher than those from healthy cows after in vitro infection with M. avium subsp. paratuberculosis. The addition of exogenous IL-10 and TGF-beta to PBMC isolated from healthy cows inhibited the bactericidal activity of these cells as evidenced by the increased number of viable M. avium subsp. paratuberculosis recovered from these cultures compared to cell cultures containing medium alone. These data suggest important immune regulatory roles for IL-10 and TGF-beta during infection with M. avium subsp. paratuberculosis that may be directly related to their effects on macrophage activation and killing of M. avium subsp. paratuberculosis.

Coordinate cytokine gene expression in vivo following induction of tuberculous pleurisy in guinea pigs

Tuberculous pleurisy is a severe inflammatory response induced by Mycobacterium tuberculosis organisms that have escaped from lung granulomata into the pleural space during pulmonary infection. We have used the guinea pig model of tuberculous pleurisy to examine several aspects of the immune response to this antigen-specific inflammatory event. Pleurisy was induced by injection of heat-killed M. tuberculosis H37Rv directly into the pleural space of guinea pigs previously vaccinated with M. bovis BCG. Four animals were euthanized each day over a period of 9 days. Fluid in the pleural cavity was analyzed for transforming growth factor beta 1 (TGF-beta 1) and total interferon (IFN) protein levels. In addition, RNA was obtained from pleural cells and examined for TGF-beta 1, tumor necrosis factor alpha (TNF-alpha), IFN-gamma, and interleukin-8 (IL-8) expression by real-time PCR. Finally, pleural cells were examined for the ability to proliferate in response to concanavalin A and purified protein derivative (PPD) in vitro. In the pleural fluid, TGF-beta 1 protein concentrations increased over the course of the inflammatory response while IFN protein levels were not significantly altered. Expression of TGF-beta 1 mRNA peaked on days 3 and 4, and IFN-gamma mRNA expression peaked on day 3 and then returned to background levels. TNF-alpha mRNA expression was highest on days 2 to 4, and IL-8 mRNA levels remained elevated between days 2 and 5, peaking on day 3 before returning to background levels. PPD-induced proliferative responses were evident by day 3 and remained present throughout the study. Analysis of cytokine expression during tuberculous pleurisy may lead to a better understanding of the self-healing nature of this manifestation of tuberculosis.

Differential effects of control and antigen-specific T cells on intracellular mycobacterial growth

We investigated the effects of peripheral blood mononuclear cells expanded with irrelevant control and mycobacterial antigens on the intracellular growth of Mycobacterium bovis bacillus Calmette-Guérin (BCG) in human macrophages. More than 90% of the cells present after 1 week of in vitro expansion were CD3(+). T cells were expanded from purified protein derivative-negative controls, persons with latent tuberculosis, and BCG-vaccinated individuals. T cells expanded with nonmycobacterial antigens enhanced the intracellular growth of BCG in suboptimal cultures of macrophages. T cells expanded with live BCG or lysates of Mycobacterium tuberculosis directly inhibited intracellular BCG. Recent intradermal BCG vaccination significantly enhanced the inhibitory activity of T cells expanded with mycobacterial antigens (P < 0.02), consistent with the induction of memory-immune inhibitory T-cell responses. Selected mycobacterial antigens (Mtb41 > lipoarabinomannan > 38kd > Ag85B > Mtb39) expanded inhibitory T cells, demonstrating the involvement of antigen-specific T cells in intracellular BCG inhibition. We studied the T-cell subsets and molecular mechanisms involved in the memory-immune inhibition of intracellular BCG. Mycobacteria-specific gammadelta T cells were the most potent inhibitors of intracellular BCG growth. Direct contact between T cells and macrophages was necessary for the BCG growth-enhancing and inhibitory activities mediated by control and mycobacteria-specific T cells, respectively. Increases in tumor necrosis factor alpha, interleukin-6, transforming growth factor beta, and vascular endothelial growth factor mRNA expression were associated with the enhancement of intracellular BCG growth. Increases in gamma interferon, FAS, FAS ligand, perforin, granzyme, and granulysin mRNA expression were associated with intracellular BCG inhibition. These culture systems provide in vitro models for studying the opposing T-cell mechanisms involved in mycobacterial survival and protective host immunity.

Correlation of serum tumor necrosis factor-alpha, interleukin-4 and soluble interleukin-2 receptor levels with radiologic and clinical manifestations in active pulmonary tuberculosis

The precise clinical manifestations of tuberculosis are likely to result from a complex interaction between the host and the pathogen. We took serum samples from a group of patients with a variety of clinical and radiological stages of pulmonary tuberculosis in order to characterize tumor necrosis factor-alpha (TNF-alpha), interleukin-4 (IL-4) and soluble interleukin-2 receptor (sIL-2R) response. We further evaluated whether the levels of TNF-alpha, IL-4 and soluble IL-2R are related with each other, and also evaluated the levels of TNF-alpha, IL-4 and sIL-2R after anti-tuberculosis therapy and relation with radiologic scores. Forty-three inpatients with active pulmonary tuberculosis and 19 healthy controls participated in the study. Patients were divided into four categories radiologically on chest X-ray (minimal, moderate-advanced, far-advanced and with miliary infiltration). Concentrations of TNF-alpha (20.9+/-10/15.4+/-8 pg/ml) and sIL-2R (2569+/-842/1444+/-514 pg/ml) were statistically different between patients and controls (p=0.02 and p=0.0001, respectively). Before chemotherapy there was a positive correlation between TNF-alpha and sIL-2R (r=0.34), but there was no correlation between IL-4 and TNF-alpha, and between IL-4 and sIL-2R (r=-0.23 and r=-0.22). The TNF-alpha level was not statistically different in four groups before and after chemotherapy. Results of this study provided some evidence confirming the previously reported role of TNF-alpha, IL-4 and sIL 2R in the control of tuberculosis, but these cytokines were not found related with disease severity.

Transforming growth factor-beta decreases survival of Mycobacterium bovis-activated T cells

BACKGROUND

A comprehensive understanding of the immune response induced by Mycobacterium bovis Bacille Calmette-Guérin in activation of protective T cells against tuberculosis is important to develop effective therapies to combat this disease. In this study, our experiments were designed to determine effects of transforming growth factor (TGF)-beta on M. bovis-induced T-cell activation and survival.

METHODS

Fluorescence-activated cell sorter (FACS) analysis was used for detection of apo-ptotic cells by three different methods: 1). scattered light change during early phase of apoptosis; 2). detection of hypodiploid DNA, or 3). terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) technique. Quantification of positively stained population was based on samples stained with isotype control antibodies analyzed on a FACScan.

RESULTS

TGF-beta added at initiation of culture did not alter percentage of viable cells. By contrast, TGF-beta added 72 h post-activation decreased percentage of viable cells. This effect was statistically significant (p <0.05). Furthermore, addition of anti-TGF-beta MoAb together with TGF-beta abolished the ability of this cytokine to decrease survival in post-activated human T cells. Role of TGF-beta on post-activated human T cells was further confirmed by staining apoptotic nuclei with propidium iodide, which detects late events of apoptosis, and by DNA fragmentation determined using TUNEL assay. Interestingly, TGF-beta did not promote Fas-mediated killing. Finally, TGF-beta increased apoptosis of CD4(+) T cells after mycobacterial stimulation.

CONCLUSIONS

This study indicated an important role for TGF-beta in suppression of protective immune response against M. bovis by promoting elimination of post-activated T cells. Furthermore, results showed that TGF-beta had no direct effect on M. bovis-induced up-regulation of Fas (CD95).

Immunohistochemical distribution of epithelioid cell, myofibroblast, and transforming growth factor-beta1 in the granuloma caused by Mycobacterium avium intracellulare complex pulmonary infection

The present study was designed to evaluate the distribution of epithelioid cells, myofibroblasts, and TGF-beta1 in the formation of granuloma caused by Mycobacterium avium intracellulare complex (MAC) lung infection. A retrospective study was performed for 9 cases of positive MAC culture in which lung resections were performed between January 1989 and August 1999. Resected lung specimens were evaluated histologically and immunohistochemically for CD68 (stain for monocytes and macrophages, and epithelioid cells) and alpha-smooth muscle actin as well as vimentin (stain for myofibroblasts), and TGF-beta1 was performed. When granuloma was initially formed, no myofibroblasts were found, but as caseous necrosis appeared, the thin epithelioid cell layer was detected and the outer myofibroblast layer gradually became thick. In the cavitary wall, the layer of epithelioid cells and multinucleated giant cells surrounded necrosis, and was associated with the outer layer of myofibroblasts. In addition, the anti-TGF-beta1 antibody stained the cytoplasm of epithelioid cells and multinucleated giant cells, preceding the advent of myofibroblasts. In summary, our present study evaluated distributions of epithelioid cells, myofibroblasts, and TGF-beta along with the morphogenesis of granuloma, and clearly demonstrated the immunohistochemical difference between granuloma with caseous necrosis and granulomas without caseous necrosis.

Innate immunity to Mycobacterium tuberculosis

The different manifestations of infection with Mycobacterium tuberculosis reflect the balance between the bacillus and host defense mechanisms. Traditionally, protective immunity to tuberculosis has been ascribed to T-cell-mediated immunity, with CD4(+) T cells playing a crucial role. Recent immunological and genetic studies support the long-standing notion that innate immunity is also relevant in tuberculosis. In this review, emphasis is on these natural, innate host defense mechanisms, referring to experimental data (e.g., studies in gene knockout mice) and epidemiological, immunological, and genetic studies in human tuberculosis. The first step in the innate host defense is cellular uptake of M. tuberculosis, which involves different cellular receptors and humoral factors. Toll-like receptors seem to play a crucial role in immune recognition of M. tuberculosis, which is the next step. The subsequent inflammatory response is regulated by production of pro- and anti-inflammatory cytokines and chemokines. Different natural effector mechanisms for killing of M. tuberculosis have now been identified. Finally, the innate host response is necessary for induction of adaptive immunity to M. tuberculosis. These basic mechanisms augment our understanding of disease pathogenesis and clinical course and will be of help in designing adjunctive treatment strategies.

Cytokine transcripts in pediatric tuberculosis: a study with bronchoalveolar cells

Pediatric tuberculosis (TB) differs from adult TB in many features. To date, cytokine expression has not been studied in children with TB. The relative amounts of the various cytokines released at the site of infection may be important determinants of TB disease development and pathology. We determined cytokine transcripts in bronchoalveolar cells (BACs) recovered from 9 children presenting with TB and from 9 children with pulmonary diseases other than TB. An RT-PCR-based method was developed to quantify the mRNAs encoding six cytokines (IFN- gamma, IL-12, TNF- alpha, IL-10, IL-4, TGF- beta 1) known to play key roles in mycobacterial infections. Expression of mRNA encoding TGF- beta, TNF- alpha and IFN- gamma was statistically significantly higher in BACs from children with TB than in BACs from children with other pulmonary diseases; whereas the levels of mRNA transcription for TGF- beta is high, the levels of mRNA transcription for IFN- gamma and TNF- alpha remain low. All children had low levels of mRNA for IL-12(p40). IL-4 was barely detectable in all cases. Children with miliary TB had high levels of IL-10 transcripts and low levels of mRNA encoding TGF- beta. The immunosuppressive cytokines TGF- beta and IL-10, are overproduced in children with non-miliary TB and miliary TB respectively and are probably involved in the progression of the disease. These data suggest that Th1 responses are reduced in children with TB.

Circulating TNF-alpha, TGF-beta, and IL-10 in tuberculosis patients and healthy contacts

Levels of tumour necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta, and interleukin (IL)-10 in plasma of pulmonary tuberculosis (TB) patients and healthy contacts and plasma and pleural fluid of patients with tuberculous pleuritis were examined by enzyme immunoassay. Plasma TNF-alpha and IL-10 were elevated to significant levels in healthy contacts. High levels of TGF-beta and IL-10 were also detected in plasma from TB patients and healthy contacts. Pleural fluid contained all three cytokines with the level of IL-10 being highest followed by TGF-beta and TNF-alpha. Plasma of tuberculous pleuritis patients also had detectable levels of the three cytokines. Increased levels of TNF-alpha in plasma of contacts and to some extent pleural fluid of pleuritis patients, is perhaps to limit the infection, while elevated IL-10 in plasma of TB patients and contacts and pleural fluid would perhaps modulate excess proinflammation. Elevated TGF-beta in TB patients suggests its role in the immunopathogenesis.

Influence of disease severity on nitrite and cytokine production by peripheral blood mononuclear cells (PBMC) from patients with pulmonary tuberculosis (TB)

Earlier studies in patients with pulmonary TB have revealed a higher production of Th1 cell type cytokines in moderate TB, with predominant Th2-like responses in advanced disease. Given the influence of IL-12 in T cell differentiation, as well as the roles of transforming growth factor-beta (TGF-beta), nitric oxide and tumour necrosis factor-alpha (TNF-alpha) in the immune response against intracellular pathogens, we decided to analyse the interferon-gamma (IFN-gamma), IL-4, IL-12, TGF-beta, TNF-alpha and nitrite concentrations in culture supernatants of PBMC from TB patients showing different degrees of lung involvement. The sample population comprised 18 untreated TB patients with either moderate (n = 9) or advanced (n = 9) disease and 12 age- and sex-matched healthy controls (total population (patients and controls) 12 women, 18 men, aged 37 +/- 13 years (mean +/- s.d.)). PBMC were stimulated with whole sonicate from Mycobacterium tuberculosis and the supernatants were collected on day 4 for measurement of cytokine and nitrite levels. Antigen-stimulated IFN-gamma, TGF-beta and TNF-alpha production was found to be significantly increased in TB patients, both moderate and advanced, compared with the controls. Levels of IFN-gamma were significantly higher in moderate disease than advanced cases, whereas advanced cases showed significantly higher IL-12, TGF-beta and TNF-alpha concentrations when compared with cases of moderate TB. Nitrite levels were also increased in TB patients and the increase was statistically significant when advanced cases were compared with controls. These findings may contribute to a clearer picture of the net effect of cytokine interactions in TB, essential for a better understanding of the immunopathological mechanisms underlying the distinct clinical forms of the disease.

Increased cortisol: cortisone ratio in acute pulmonary tuberculosis

To evaluate a possible role for altered cortisol metabolism in mediating the immunoparesis associated with progressive tuberculosis (TB), we have studied the hypothalamic-pituitary-adrenal axis, and the activities of the 11beta-hydroxysteroid dehydrogenases (11-HSDs) that interconvert active cortisol and inactive cortisone. In active pulmonary tuberculosis (PTB), the ratio of cortisol/cortisone metabolites in 24-h urine showed a shift towards active cortisol (ratio, 1.19 +/- 0.1, n = 16 versus 0. 89 +/- 0.05 in cured pulmonary tuberculosis (CTB), n = 13, p < 0. 01; and 0.78 +/- 0.04 healthy volunteers (HV), n = 11, p < 0.005). Conversion of cortisone (administered as 25 mg orally) to cortisol in peripheral plasma was higher in PTB (peak 1,157 +/- 55 nM, n = 14 versus 862 +/- 50 nM in CTB, n = 10, p < 0.005, and 882 +/- 73 nM in HV, n = 10; p < 0.005). Cortisol/cortisone ratio was increased in bronchoalveolar lavage fluid in PTB (7.73 +/- 1.48, mean +/- SE, n = 13) compared with HV (4.05 +/- 0.38, n = 11, p < 0.05) but was not different in plasma (PTB, 3.25 +/- 0.68; HV, 4.01 +/- 0.92). Responses of plasma cortisol to dexamethasone, CRH stimulation, and multidose ACTH stimulation were not different. These data suggest that in pulmonary tuberculosis, central control of glucocorticoid production is normal but that peripheral metabolism, in particular in the lung, is deviated in favor of the active metabolite cortisol. This offers a possible mechanism to explain the immunoparesis observed in progressive pulmonary tuberculosis.

Effective preexposure tuberculosis vaccines fail to protect when they are given in an immunotherapeutic mode

Two vaccine formulations previously shown to induce protective immunity in mice and prevention of long-term necrosis in guinea pigs were tested as potential immunotherapeutic vaccines in mice earlier infected by aerosol with Mycobacterium tuberculosis. Neither vaccine had any effect on the course of the infection in the lungs, but both reduced the bacterial load in the spleen. Similarly, inoculation with Mycobacterium bovis BCG had no effect whatsoever and, if given more than once, appeared to induce an increasingly severe pyogranulomatous response in the lungs of these mice.

Defining the requirements for immunological control of mycobacterial infections

Tuberculosis remains a major public health problem throughout the world. Research into the immunological basis of the host-pathogen relationship has recently benefited from the fascinating convergence of genetic data from mouse models and from humans. Latency - the seemingly quiescent phase of bacterial persistence - is the central problem in controlling tuberculosis and will be the next frontier of research.

The immunopathology of siliconosis. History, clinical presentation, and relation to silicosis and the chemistry of silicon and silicone

Recent evidence confirms the fundamental involvement of the human immune system in the reaction to implantation of silicone-based medical devices. An as yet-to-be particularized epitope of many complex substances sharing siloxane structures is presented through the MHC-II apparatus with development and retention of T cell memory. This memory can be tested for in practical terms using one or more forms of silica, which links the immuno-histopathology and autoimmune attributes of "silicosis" with those of "siliconosis." The lesions of siliconosis are typical of those for persistent antigens and delayed, cell mediated hypersensitivity. The basic descriptive pathology of the reaction to silicone has been known since soon after introduction of silicones in medical procedures, with the exception of some details related to the more recent discoveries on the role of cytokines in the immunopathic process. The clinical consequences of siliconosis are common and can be severe in some individuals implanted with silicone devices.