Immunotherapy with natural interleukins and/or thymosin α1 potently augments T-lymphocyte responses of hydrocortisone-treated aged mice

Abstract Cytokines and thymic hormones are thought to play critical roles in the regulation of T-lymphocyte development and function. In an effort to determine the effectiveness of such agents in an immunotherapeutic strategy, we employed aged mice in a hydrocortisone treatment model to generate an immunodeficient state and to study its reconstitution. Mice were given five daily injections of a natural cytokine mixture (NCM), recombinant interleukins (rIL-1, rIL-2) or their combination, thymosin α 1 or fraction 5 (Tα 1 , TF5), or the combinations of NCM plus Tα 1 and of NCM plus TF5. Spleen and thymus weights were obtained and the cellular responses to stimulation in vitro with NCM, IL-1, IL-2 and mitogens (PHA and Con A) were assayed. Both NCM and Tα 1 in vivo treatment augmented thymocyte and splenocyte in vitro responses to both interleukins and mitogens. Neither treatments with equivalent doses of rIL-1, rIL-2 nor their combination, nor TF5 achieved similar results. Of all the treatments, only NCM plus Tα 1 augmented spleen weight; none augmented thymus weight. Surface marker analyses of T-lymphocytes and subsets indicate that treatment of mice with NCM plus Tα 1 increased spleen T-cell numbers of both CD4 and CD8 positive cells significantly. These data indicate that NCM and Tα 1 alone and in combination may be therapeutically useful to restore T-lymphocyte number or function in secondary immunodeficiency.