Immunohistochemical analysis of cytokines and apoptosis in tuberculous lymphadenitis

Abstract

SummaryRelatively little is known about the effector mechanisms whereby the human immune system controls Mycobacterium tuberculosis infection. In this study we elaborate on the immune response and mechanisms of persistence of mycobacteria in lesions by analysing, using immunohistochemistry, the expression of cytokines [tumour necrosis factor-a (TNF-a), interleukin-10 (IL-10), transforming growth factor-b (TGF-b) and interferon-c (IFN-c)], apoptotic cells and apoptosis-related proteins [Bcl2, Bax, Fas ligand (FasL) and Fas] in the human tuberculous lymphadenitis lesions. The expression of apoptosis-related proteins has been shown to be exploited by mycobacteria to evade the immune response and persist in the host. Foreign body (FB) granulomas were used as controls. In tuberculosis (TB) granulomas, epithelioid cells and multinucleated giant cells expressed cytokines differently. In epithelioid cells, the numbers of TNF-a-, IL-10-and TGF-b-stained cells were higher than IFN-c-stained cells (P < 0Á01). TGF-b and FasL were strongly expressed in the necrotic centres as compared with other cytokines. More giant cells expressed IL-10 and TGF-b than expressed TNF-a and IFN-c (P < 0Á01). Staining of consecutive sections revealed that some giant cells expressed IL-10 but not TNF-a. Apoptotic TB giant cells correlated positively with the expression of TNF-a, IFN-c and TGF-b, but not with the expression of IL-10. The percentage of giant cells expressing Bax was lower than those expressing Fas, unlike the epithelioid cells, suggesting that TB giant cells are less susceptible to apoptosis. Compared with FB giant cells, there were fewer TB giant cells showing TNF-a, IFN-c, FasL, Fas expression or undergoing apoptosis (P < 0Á05). Taken together, these observations show that the cellular microenvironment of TB granulomas down-regulates microbicidal functions, favouring bacillary survival and persistence. TGF-b and FasL may be responsible for tissue destruction. The giant cells, being less susceptible to apoptosis, may remain a continuous source of pro-inflammatory cytokines, causing immune pathology.

Expression of apoptosis‐related genes in an Ethiopian cohort study correlates with tuberculosis clinical status

“…However, FasL mRNA was higher in both CD14 1 and CD14 À cells from TB patients, suggesting a broad upregulation of this molecule in this cohort. This observation is consistent with earlier reports from human and murine M. tuberculosis infections [38,40,[42][43][44]. …”

Elevated N-terminal pro-brain natriuretic peptide in Mycobacterium tuberculosis pulmonary infection without myocardial dysfunction

“…Cytokine expression in tuberculosis correlates with cell type. Thus, granulomas, epithelioid cells and multinucleated giant cells have their own cytokine expression (31). Active pulmonary tuberculosis and subsequent alveolar inflammation result in the release of tumour necrosis factor-alpha (TNF-α) and interleukin-1 beta identified in bronchoalveolar fluid (32).…”

Reduced apoptosis and increased inflammatory cytokines in granulomas caused by tuberculous compared to non-tuberculous mycobacteria: role of MPT64 antigen in apoptosis and immune response

“…Apoptosis-related protein FasL with antibodies were obtained from Alexis Biochemicals (San Diego, CA, USA) and Fas, Bax and Bcl-2 with antibodies from Santa Cruz Biotechnology. All the antibodies were mouse monoclonal antibodies except anti-TGF-b and anti-caspase-3, which were rabbit polyclonal antibodies as described previously [27].…”

“…We have studied previously the immune response in human granulomatous lymphadenitis lesions, where the diagnosis of TB was made on the basis of histology [27]. However, tuberculous or non-tuberculous mycobacteria can give similar histological features [28].…”