Restoration of immunocyte functions by thymosin alpha 1 in cyclophosphamide induced immunodeficient mice

Thymosin alpha1 (T alpha1) is an oligopeptide hormone originally isolated f rom the thymus gland, and has been reported to have stimulating effects on the differentiation of T cells and NK cells. These immunostimulating proper ties have been considered to be useful for improving immune disorders assoc iated with various diseases including cancer, AIDS and hepatitis. Here, we characterized immunostimulating properties of Tal in experimental immunodef iciency of mice that was induced by the administration of cyclophosphamide (CY). Repeated injection of 30-300 mug/kg/day of Tal after CY-treatment sig nificantly accelerated the restoration of the reduced number of CD4(+)CD8() T cells in the thymus. T alpha1 administration was effective in restoring the suppressed activities of helper T cells and cytotoxic T cells in CY-tr eated mice. Tal also had stimulating effects on reduced activity of lymphok ine-activated killer cells in CY-treated mice. These results indicate that T alpha1 is stimulatory for both humoral and cellular immune responses, thu s providing the immunological basis for the clinical benefit of this compou nd.