The in vitro effect of a calf thymus extract on the peripheral blood lymphocytes of patients with warts.

T and B lymphocyte populations were evaluated in forty-one patients with multiple recurring warts. Active rosettes (T-Ea) and total T lymphocytes (T-Et) were significantly decreased. The in vitro effect of a calf thymus extract (TP-I) on peripheral blood lymphocytes was evaluated in thirty-three patients. A statistically significant increase in E-rosette forming cells was observed in twenty-three patients (69%). Serum blocking factors were not found in the patients with a positive response to TP-I, which suggests the possibility of a thymic hormone deficiency. In the case of non-responders to TP-I, on the other hand, an anti-lymphocyte antibody capable of directly blocking the hormone receptors on the undifferentiated lymphocytes may be postulated.