Actin activity is high in the immunocompetent fraction of thymocytes.

We have shown previously that actin activity of lymphocytes correlates with their migratory abilities. To determine whether any subpopulation of thymocytes would possess the potential for peripheral migration, sheep thymocytes were separated into four fractions by Percoll discontinuous gradient centrifugation and actin activity of each fraction was determined. The fraction enriched for immunocompetent medullary-type cells showed the highest actin activity among thymocytes, but the activity was significantly lower than that of peripheral lymphocytes. The implications of the observation in relation to thymocyte migration is discussed.