en Immunology Immunology Original Research Original Research Human brucellosis is a major health problem in developing countries. A number of patients with human brucellosis do not recover from the acute stage of the disease and pass into the chronic form. Since the pathophysiology of this change is not well understood, we studied the T-cell subsets during the acute, subacute and chronic forms of human brucellosis. In this study we found alterations in T-Iymphocyte subsets and in the CD4/CD8 ratio in subacute and chronic brucellosis while no significant change was found in T-cell subsets in acute brucellosis. We believe that this alteration of T-cell subsets is important in the pathophysiology of brucellosis, but it is not clear whether brucella cause this change or a primary immunodysfunction in patients with a disturbance in T-cell subset regulation prevents recovery from acute brucellosis and leads to the development of chronic brucellosis. Brucellosis, CD4, CD8, T-Iymphocyte, Alkaline phosphatase anti-alkaline phosphatase (APAAP) method 191 194 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-425&slc_lang=en&sid=1 AA POURFATHOLLAH 20031947532846005318 20031947532846005318 Yes From the Dept. of Immunology, School of Medical Sciences, Tarbiat Modarress University, Tehran MB ESLAMI 20031947532846005319 20031947532846005319 No the Departments of Pathobiology Tehran University of Medical Sciences, AR YALDA 20031947532846005320 20031947532846005320 No Infectious Diseases, Tehran University of Medical Sciences, AF SARRAF NEJAT 20031947532846005321 20031947532846005321 No the Departments of Pathobiology Tehran University of Medical Sciences,