The study “Immunological Evidence for the Role of Mycobacteria in Sarcoidosis: A Meta-Analysis,” published recently in PLOS One, links some patients with sarcoidosis to the development of the disease and the presence of mycobacterium tuberculosis, which causes tuberculosis.
Mycobacterium tuberculosis is the second leading cause of death by infectious disease, preceded only by HIV, among adults worldwide. The bacterium lives and replicates inside specialized cells, called macrophages. In the lungs, the macrophage response to the infection leads to the formation of a growth of abnormal tissue, a granulomatous structure, called tubercle.
Previous studies reported the presence of mycobacterium tuberculosis in samples extracted from several sarcoidosis patients. Those studies relied on the analysis of mycobacterial DNA that supported a link between mycobacteria and sarcoidosis.
Recently, new interest among researchers rose to examine immunological evidence of mycobacterial antigens in sarcoidosis patients, and a few of those analysis also pointed toward mycobacterium tuberculosis antigens (bacteria that induce an immune response) as involved in the development of sarcoidosis. But, the relationship between sarcoidosis and mycobacterium tuberculosis is still hotly debated.
For the recent study, employing a meta-analysis of statistical data, a team of researchers assessed immunological evidence that points to the possible role of mycobacteria in the development of sarcoidosis.
Researchers used articles published between January 1990 and October 2015 in several databases, including PubMed, Embase and Cochrane Library. In total, the analysis comprised 13 case-control studies that included 733 individuals.
The team noted a higher positive incidence of an immune response (either cell-mediated response or antibody-mediated immune response) against mycobacterium tuberculosis specific antigens in the group of sarcoidosis patients, when compared to the control group. Specifically, the measure of association between an exposure and an outcome for the positive incidence of T-cell response in the patients with sarcoidosis, versus controls, was 5.54.
The review concluded that some association between mycobacterium tuberculosis and sarcoidosis exists. Although mycobacteria was not detected in all cases of sarcoidosis, these results suggest that mycobacterium tuberculosis is an important factor in the development of the disease.