Rat thymocyte subpopulations: heterogeneity of the fetal calf serum dependent rosette forming cells.

We demonstrate heterogeneity within a rat thymic cortical population, the fetal calf serum dependent rosette forming cells. Approximately half of these cells are guinea pig serum sensitive. Guinea pig serum sensitive and insensitive rosette forming cells show different distribution patterns on a continuous gradient of Percoll. They contain different amounts of TdT enzyme and regenerate with different time kinetics following sublethal irradiation. These data demonstrate new aspects of heterogeneity within the rat thymic cortical population.