In vitro and in vivo studies with thymosin in cancer patients.

Thymosin, fraction V, prepared by the method of Goldstein et al., was studied in in vitro lymphocyte cultures with cells obtained from normal subjects and patients with disseminated cancer. Thymosin lowered blastogenic activity in some patients, did not affect it in others, and increased counts in still others. There was a statistically significant depression in baseline (prethymosin) counts from both normals and patients when individuals whose counts increased in the presence of thymosin were compared with other subjects. We conclude that thymosin tended to raise depressed blastogenesis into the normal range without causing supranormal activity or without itself acting as a mitogen or antigen. Eighty-two in vivo courses in thymosin were given to 32 patients. Analysis of the first thymosin courses in these 32 patients shows that immunologic reconstitution occurred in patients with originally depressed T-cell function and numbers, whereas little change was apparent in patients with initially intact tests of T-cell activity. Clinical effects were equivocal; however, no systematic clinical trial was conducted. Toxicity was minimal (four of the 32 patients); in each case, it consisted of inflammation at the injection site. The in vitro and in vivo results of this study suggest that thymosin therapy modulates and partially normalizes T-lymphocyte numbers and function.