Abstract
Host immune response against Mycobacterium tuberculosis is mediated by cellular immunity, in which cytokines and Th1 cells play a critical role. In the process of control of the infection by mycobacteria, TNF-alpha seems to have a primordial function. This cytokine acts in synergy with IFN-gamma, stimulating the production of reactive nitrogen intermediates (RNIs), thus mediating the tuberculostatic function of macrophages, and also stimulating the migration of immune cells to the infection site, contributing to granuloma formation, which controls the disease progression. IFN-gamma is the main cytokine involved in the immune response against mycobacteria, and its major function is the activation of macrophages, allowing them to exert its microbicidal role functions. Different from TNF-alpha and IFN-gamma, IL-10 is considered primarily an inhibitory cytokine, important to an adequate balance between inflammatory and immunopathologic responses. The increase in IL-10 levels seems to support the survival of mycobacteria in the host. Although there is not yet conclusive studies concerning a clear dichotomy between Th1 and Th2 responses, involving protective immunity and susceptibility to the disease, respectively, we can suggest that the knowledge about this responses based on the prevailing cytokine profile can help to elucidate the immune response related to the protection against M. tuberculosis.
Highlights
The genus Mycobacterium displays more than 100 known species, with a broad geographic distribution, habitat diversity, and diverse relations with other organisms, including more than 20 species presenting different degrees of pathogenicity to humans [1]
IFN-gamma is the main cytokine involved in the immune response against mycobacteria, and its major function is the activation of macrophages, allowing them to exert its microbicidal role functions
There is not yet conclusive studies concerning a clear dichotomy between Th1 and Th2 responses, involving protective immunity and susceptibility to the disease, respectively, we can suggest that the knowledge about this responses based on the prevailing cytokine profile can help to elucidate the immune response related to the protection against M. tuberculosis
Summary
The genus Mycobacterium displays more than 100 known species, with a broad geographic distribution, habitat diversity, and diverse relations with other organisms, including more than 20 species presenting different degrees of pathogenicity to humans [1]. Pulmonary tuberculosis is a global public health problem, presenting high incidence in Brazil. It is still the world’s leading cause of death from a single infectious agent. Most infections are asymptomatic and latent around 5% to 10% of infected people progress to the disease development at each year, pulmonary tuberculosis being found in most cases. Latent TB is defined as an infection with M. tuberculosis that remains within macrophages without replicate, but that retains the ability to exit latency and cause active disease when there is an interruption of the protective immune response. Several factors can trigger the development of active disease from reactivation of latent infection, which usually involves the decline of the immune response. Understanding the mechanisms involved in this response, and in particular the function of the cytokine network involved in this disease, is of significant relevance to reach advances in the development of effective control and prevention [10]
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