AbstractThirty two anergic patients with chronic brucellosis treated with a)interferon-alpha2b(group 1), b)levamisole (group 2) and c)conventional therapy(group 3) were studied. the effect of treatment on T lymphocyte blast formation in the presence of PHA, specific cell mediated immunity against brucella antigens, titers of brucella antibodies and clinical symptoms were evaluated T lymphocyte blast formation was shown to range in normal levels in all patients before treatment compared to 10 normal controls suggesting against a generalized impairment of cell mediated immunity. Titers of brucella antibodies were significantly decreased in group 1, almost significantly in group 2 and were significantly increased in group 3 at the end of treatment. A significant improvement of symptoms as well as production of leukocyte migration inhibition against brucella antigens were noted in both groups 1 and 2, in contrast to group 3. This response to treatment was however greater in group 1. These findings demonstrate that immunotherapy resulted in both clinical and immunological improvement and that interferon seems to be a more promising therapeutic approach of chronic brucellosis.