Thymus lymphocytes. Efflux and restoration phases after peripheral exposure of mice to phytohaemagglutinin.

Juvenile Swiss mice experienced significant diminutions in thymic content of both small, non-proliferating and larger, proliferating lymphocytes within 12 hours after intraperitoneal injection of phytohaemagglutinin. These alterations, which may predate alterations in lymphocyte traffic and morphology elsewhere, were interpreted as being the consequence of a massive thymus lymphocyte emigration, not of in situ cytolysis, and were effaced by intrathymic lymphocyte restoration toward control numbers by 24 hours.