Ali Ganji - Department of Immunology, Molecular and Medicine Research Center, School of Medicine, Arak University of Medical Sciences, Arak, Iran.
Ghasem Mosayebi - Department of Immunology, Molecular and Medicine Research Center, School of Medicine, Arak University of Medical Sciences, Arak, Iran.
Ehsanollah Ghaznavi-Rad - Molecular and Medicine Research Center, Arak University of Medical Sciences, Arak, Iran.
Khadije khosravi - Department of Immunology, Molecular and Medicine Research Center, School of Medicine, Arak University of Medical Sciences, Arak, Iran.
Nader Zarinfar - Tuberculosis and Pediatric Infectious Research Center, Arak University of Medical Sciences, Arak, Iran.

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 ۱ (Th۱) cells, brucellosis can advance to chronic disease in about ۱۰-۳۰% 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 CD۴+, CD۲۵+, FoxP۳+, and CD۲۵/FoxP۳+ 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 CD۴+, CD۲۵+, and FoxP۳+ T cells were also measured. Results: We found a significantly lower percentage of CD۲۵/FoxP۳+ Treg cells in CB than in the AB and control groups (p < ۰.۰۵). Also, CD۴ and CD۲۵ MFIs were significantly less in CB than in AB and controls (p < ۰.۰۵). Conclusions: We propose that the reduced number of CD۲۵/FoxP۳+ Treg cells in the CB group leads to T cell anergy and this contributes to the development of chronic infection.

Brucellosis, CD۲۵ Antigen, FoxP۳ Protein, Regulatory T cells