Partial restoration by in vivo thymosin of E-rosettes and delayed-type hypersensitivity reactions in immunodeficient cancer patients

Thymosin, fraction V, a partially purified extract of calf thymus, was administered to 14 patients with disseminated, far-advanced malignant disease. It increased the number of positive delayed-type hypersensitivity skin tests in 69% of the patients and the number of recall KLH responses in 85% of the subjects. Thymosin significantly increased T-lymphocyte rosettes in the group of patients with percentages originally less than 50%. Thymosin administration resulted in no toxic manifestations aside from local cutaneous hypersensitivity in one subject. Suggestive evidence of thymosin clinical activity was detected in three subjects. Thymosin's activity in these patients is compatible with and complementary to results obtained in vitro, in animals, and in children with certain primary immunodeficiency diseases. Thymosin may prove to be a major addition to the group of agents effective in the immunorestoration and immunotherapy of immunodeficient cancer patients.