Comparative Analysis of Mycobacterial Heat Shock Proteins-Induced Apoptosis of Peripheral Blood Mononuclear Cells in Sarcoidosis and Tuberculosis

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Abstract

Sarcoidosis (SA) is a granulomatous disorder of an unknown etiology. Mycobacterium tuberculosis heat shock proteins (Mtb-hsp), considered as causative agents, play an important role in apoptosis. A role for apoptosis has been proposed in pathogenesis of SA and tuberculosis (TB) granuloma formation but results remain controversial. Differences in Mtb-hsp-induced apoptosis between SA, TB, and healthy subjects found in this study might put some light on the etiology of SA. Early apoptotic peripheral blood mononuclear cells (PBMC) were determined in 22 SA patients, 20 TB patients, and 20 healthy volunteers by flow cytometry (Annexin-V-FITC). Our results revealed that spontaneous apoptosis of monocytes and CD8+ T-cells was comparable between tested groups. Apoptosis of unstimulated CD4+ T-cells was significantly lower in TB versus controls and insignificantly lower versus SA. Mtb-hsp- and PHA (Phytohemagglutinin)-induced monocytes apoptosis was significantly lower in TB versus controls and SA. Mtb-hsp-induced CD4+ T-cell apoptosis was significantly lower in TB versus controls and SA. There were no differences of PHA-induced CD4+ T-cell and CD8+ T-cell apoptosis between tested groups. Apoptosis of Mtb-hsp-induced CD8+ T-cells was significantly lower in TB and SA versus controls. Analysis of PBMC apoptosis before and after stimulation in each tested group revealed that, in contrast to TB, sarcoid monocytes were resistant to Mtb-hsp- and PHA-induced apoptosis and CD4+ T-cells were resistant to PHA- but not Mtb-hsp-induced apoptosis. CD8+ T-cell apoptosis, before and after Mtb-hsp or PHA stimulation, was significantly increased in all tested groups. It seems likely that dysregulated apoptosis of CD4+ T-cells and resistant apoptosis monocytes may be involved in pathogenesis of SA.

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