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Given the role of cell-mediated immune responses in resistance to mycobacteria, we sought to analyse whether there was a relationship between the severity of pulmonary tuberculosis (TB) and lymphocyte proliferation as well as in vitro cytokine production. To achieve this, 25 untreated TB patients showing mild (n = 5), moderate (n = 9) or advanced (n = 11) pulmonary disease, and 12 age-matched healthy controls (mean+/-SD, 37+/-14.5 years) were studied. Peripheral blood mononuclear cells were cultured for 5 days with 10 microg/ml whole, sonicated Mycobacterium tuberculosis (WSA) or 2.5 microg/ml Concanavalin A (Con A). Supernatants were collected on day 4, from cultures grown with or without WSA, for measurement of interferon-gamma (IFN-gamma), interleukin (IL)-4, IL-1beta and transforming growth factor-beta (TGF-beta). Antigen-specific proliferation was found to be reduced among patients and more profound in those with advanced disease who also displayed a depressed response to Con A. Patients with mild TB showed a preferential production of IFN-gamma over IL-4, gave the highest level of IFN-gamma synthesis upon specific antigen stimulation and showed increased levels of IL-1beta production. Findings in patients with moderate TB appeared compatible with a mixed production of IFN-gamma and IL-4 coexisting with a higher synthesis of TGF-beta, by comparison to patients with mild TB. Advanced disease showed the highest IL-4 and TGF-beta production, with IFN-gamma synthesis readily noticeable, yet decreased in comparison with the other patient groups. Differences in cytokine response according to the amount of lung involvement suggest a role for such mediators in the immunopathogenesis underlying the distinct clinical forms of pulmonary TB, that is a predominant T helper Th)1-like or Th2-like activity in mild or in progressive TB, respectively.

Our study investigated the circulating levels of factors involved in immune-inflammatory-endocrine-metabolic responses in patients with tuberculosis with the aim of uncovering a relation between certain immune and hormonal patterns, their clinical status and in vitro immune response. The concentration of leptin, adiponectin, IL-6, IL-1β, ghrelin, C-reactive protein (CRP), cortisol and dehydroepiandrosterone (DHEA), and the in vitro immune response (lymphoproliferation and IFN-γ production) was evaluated in 53 patients with active untreated tuberculosis, 27 household contacts and 25 healthy controls, without significant age- or sex-related differences. Patients had a lower body mass index (BMI), reduced levels of leptin and DHEA, and increased concentrations of CRP, IL-6, cortisol, IL-1β and nearly significant adiponectin values than household contacts and controls. Within tuberculosis patients the BMI and leptin levels were positively correlated and decreased with increasing disease severity, whereas higher concentrations of IL-6, CRP, IL-1β, cortisol, and ghrelin were seen in cases with moderate to severe tuberculosis. Household contacts had lower DHEA and higher IL-6 levels than controls. Group classification by means of discriminant analysis and the k-nearest neighbor method showed that tuberculosis patients were clearly different from the other groups, having higher levels of CRP and lower DHEA concentration and BMI. Furthermore, plasma leptin levels were positively associated with the basal in vitro IFN-γ production and the ConA-driven proliferation of cells from tuberculosis patients. Present alterations in the communication between the neuro-endocrine and immune systems in tuberculosis may contribute to disease worsening.

SUMMARYEarlier 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 (TGFb), nitric oxide and tumour necrosis factor-alpha (TNF-a ) in the immune response against intracellular pathogens, we decided to analyse the interferon-gamma (IFN-g), IL-4, IL-12, TGF-b , TNF-a 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-g, TGF-b and TNF-a production was found to be significantly increased in TB patients, both moderate and advanced, compared with the controls. Levels of IFN-g were significantly higher in moderate disease than advanced cases, whereas advanced cases showed significantly higher IL-12, TGF-b and TNF-a 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.

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We have investigated the relationship between cortisol and dehydroepiandrosterone (DHEA) levels and the immune response to mycobacterial antigens in peripheral venous blood, from a male population of active tuberculosis patients and age‐matched healthy controls of the same sex (HCo). Peripheral blood mononuclear cells were cultured for 36 or 96 h with whole sonicated Mycobacterium tuberculosis (WSA) for measurement of proliferation, interferon gamma (IFN‐γ) and interleukin‐10 (IL‐10) in culture supernatants. Comparisons on the in vitro mycobacterial‐driven immune responses demonstrated that TB patients had a higher IL‐10 production, a decreased lymphoproliferation and a trend to reduced IFN‐γ synthesis, in relation to HCo. Active disease was also characterized by increases in the plasma levels of glucocorticoids (GC) and reduced concentrations of DHEA which resulted in a higher cortisol/DHEA ratio respect the HCo group. Plasma DHEA levels were positively correlated with IFN‐γ values. An inverse correlation was found between the cortisol/DHEA ratio and IFN‐γ levels. Novel evidence is provided showing that the balance between cortisol and DHEA is partly responsible for the immune perturbations seen in TB patients.

Tuberculosis (TB) may be regarded as a disease in which the immune response to Mycobacterium tuberculosis, its etiologic agent, is engaged both in protection and pathology. Different T‐lymphocyte subsets are involved in the immune response against M. tuberculosis, but production of interferon‐gamma (IFN‐γ) by T cells seems to be fundamental for disease control. Th1‐type cytokine responses predominate in patients with mild or moderate forms of pulmonary TB, whereas the production of Th2‐type cytokines prevails in the severe disease. Since the immune response fails to definitely eradicate the pathogen, a chronic infection is established, and it is likely that a broad range of regulatory mechanisms operate in this situation. Cytokines released during the course of an immune response activate the hypothalamus‐pituitary‐adrenal axis leading to the production of glucocorticoids and dehydroepiandrosterone (DHEA), with known immunomodulatory effects. TB patients exhibit increased concentrations of interleukin‐6 and cortisol in plasma, reduced DHEA and testosterone levels, together with remarkably increased growth hormone concentrations that were not accompanied by an expected raise in insulin‐like growth factor‐1. Significant increases in estradiol, prolactin, and thyroid hormone concentrations were also detected in patients. Cortisol inhibits the mycobacterial antigen‐driven proliferation and IFN‐γ production, whereas DHEA suppresses transforming growth factor beta production by lymphoid cells from TB patients with advanced disease. Furthermore, supernatants from cultures of M. tuberculosis‐stimulated mononuclear cells of TB patients inhibit DHEA secretion by a human adrenal cell line. This type of immuno‐endocrine interactions may affect the control of tissue damage and the development of protective immune responses, partly accounting for disease aggravation.

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