Thymosin-Induced Human Serum Factor Increasing Cyclic AMP

Abstract

Thymosin has virtually no in vitro effect on cyclic AMP levels in thymocytes and seems not to react with either the β-adrenergic receptor or with the putative human serum thymic factor (SF) receptor. However, when thymosin is injected into patients lacking SF activity, it induces the appearance of a serum factor which increases cellular cyclic AMP levels in thymocytes in vitro. This factor appears to act on a membrane site distinct from the β-adrenergic receptors.