Radiation Recovery of Long-Lived Lymphocytes in the Rat

Rats were given 300 rads total body irradiation and the recovery time of the long-lived lymphocyte pool was determined. The mobilizable lymphocyte pool was measured by thoracic duct lymphocyte drainage. The cell content of the superficial cervical and mesenteric lymph nodes was also determined. Additionally, the transformation response of thoracic duct lymphocytes to pokeweed mitogen was tested to assess the recovery of immunologic competence of the irradiated animals. It was found that the lymphocyte pool was in process of recovery at one month and completely recovered by two and three months after 300 rads total body irradiation. The transformation response of the thoracic duct lymphocytes of animals was tested after irradiation and was equal to that of unirradiated control animals. The slow recovery of the lymphocyte pool, which is thought to involve a two-step bone marrow-thymus pathway of reconstituting cells, is consistent with the normal kinetics of the long-lived lymphocyte pool.