The Migration of Cells to the Thymus

Abstract
The specific activity of thymic DNA was determined in mice given a single intraperitoneal dose of tritiated thymidine following whole-body irradiation, thymic irradiation and thymic chilling. In normal mice the specific activity of the DNA remained unchanged for 24 hr. following infection. After 500 R whole-body irradiation the DNA synthesizing capacity of the thymus fell more steeply than after irradiation of the thymus alone. The specific activity of the DNA labelled while the thymus was chilled by means of a ''cold finger'' was reduced to 23.6% of the normal but rose progressively onrewarming. These results were explained on the basis of an influx into the thymus of cells originating elsewhere in the body.