ZINC INDUCES THYMULIN SECRETION FROM HUMAN THYMIC EPITHELIAL-CELLS IN-VITRO AND AUGMENTS SPLENOCYTE AND THYMOCYTE RESPONSES IN-VIVO

Zinc is incorporated into zinc-thymulin by the thymus and in this form is a critical hormonal regulator of cellular immunity. In the absence of serum, zinc induces human thymic epithelial cells (TEC) to secrete a factor which promotes the expansion of interleukin-2 (IL-2) recepto r positive human peripheral blood lymphocytes in response to a low dos e of phytohemagglutinin (PHA). This factor is removed by antithymulin antisera plus filtration and is thus presumed to be zinc-thymulin. Int raperitoneal treatment of hydrocortisone treated aged mice with zinc-t hymulin (100 ng/day x5) resulted in mild augmentation of splenocyte bu t not thymocyte responses in vitro to IL-1, IL-2, and natural cytokine mixture (NCM) and to PHA and concanavalin A (Con A) (average increase 40%). Like zinc-thymulin treatment, oral ingestion of zinc (72 mu g/d ay x 5) resulted in augmentation of splenocyte IL responses; in contra st, it augmented thymocyte responses to all stimuli (average increase 100%). These preliminary experiments indicate that treatment with zinc may have immunotherapeutic relevance, particularly in the aged and st ressed organism.