Effect of thymosin and irradiation on immune modulation in head and neck and esophageal cancer patients.

Fifty-five patients with squamous cell carcinoma of the head and neck and esophagus were evaluated prior to irradiation and thymosin fraction 5 therapy. Immunity prior to treatment, as measured by total lymphocyte count, E and EAC rosettes, lymphocyte stimulation with phytohemagglutinin (PHA) and in mixed leukocyte culture (MLC) with allogeneic cells, delayed hypersensitivity skin tests, and quantitative serum immunoglobulins, was comparable and normal in the 40 control patients and in the 15 thymosin-treated patients. After irradiation, significant depression (P less than 0.01) was demonstrated in cellular immunity in both groups of patients with decreased T- and B-cell numbers and depressed phytohemagglutinin and MLC stimulation. Six months after irradiation, our preliminary results suggest that the thymosin-treated patients may be reversing their immunosuppression by a return of MLC function and positivity of delayed hypersensitivity skin tests. The ultimate effect of thymosin on disease control and survival remains uncertain.