Evaluation of Regulatory T Cells in Patients with Acute and Chronic Brucellosis

Background: Brucellosis is one of the most common chronic diseases, with widespread distribution. In spite of cell-mediated immunity (CMI) modulated mainly via activated T-helper type 1 (Th1) cells, brucellosis can advance to chronic disease in about 10-30% of cases. Regulatory T cells (Treg cells) are involved the immune response to brucellosis; however, their role, particularly in the change from the acute to the chronic phase, have not yet been elucidated. The main hypothesis of this study was that Treg cells play critical roles in the progression of brucellosis from the acute to the chronic phase. Methods: Forty-eight unrelated subjects participated in this case-control study. The percentages of CD4+, CD25+, FoxP3+, and CD25/FoxP3+ T cells in the peripheral blood mononuclear cells (PBMCs) of acute (AB) and chronic brucellosis (CB) patients and healthy controls were determined by flow cytometry. The mean florescence intensities (MFIs) of CD4+, CD25+, and FoxP3+ T cells were also measured. Results: We found a significantly lower percentage of CD25/FoxP3+ Treg cells in CB than in the AB and control groups (p < 0.05). Also, CD4 and CD25 MFIs were significantly less in CB than in AB and controls (p < 0.05). Conclusions: We propose that the reduced number of CD25/FoxP3+ Treg cells in the CB group leads to T cell anergy and this contributes to the development of chronic infection.