Thymus cell migration in a prostaglandin-mediated system.

Prostaglandin (PG)-mediated T cell traffic and the nature of these emigrant T cells were analyzed by using a fluorescent activated cell sorter. Administration of indomethacin (INDO), an inhibitor of PG synthesis, increased the number of splenic T cells in normal mice but not in adult-thymectomized mice. An increase in thymus cell migrants in peripheral blood lymphocyte and splenic cell populations of mice pretreated with INDO were detected, using the method of in situ labelling of thymocytes with fluorescein diacetate. These results indicate that the increase in the T cell population in the spleen by INDO treatment results from the increase in thymus cell migration to the spleen. Such recent emigrants in the spleen were thought to have been derived from the thymus cortex, judging from the response to phytohemagglutinin and intracellular terminal deoxynucleotidyl transferase activity; however, they expressed a Thy-1 level similar to that found on peripheral T cells. These results suggested that a cortical thymocyte population was recruited from the thymus to the spleen by a PG-mediated system, but its Thy-1 level rapidly changed to that found on the peripheral T cell population.