Characterization of mouse thymocyte subpopulations by the enzymatic marker 20-alpha-hydroxysteroid dehydrogenase: differential responses to IL-1 and IL-2.

The responses of thymocytes to Concanavalin A (Con A), and interleukin 1 (IL-1), interleukin 2 (IL-2) and phorbol myristate acetate (PMA) were investigated. The enzyme 20-alpha-hydroxysteroid dehydrogenase (20 alpha SDH) was used as a marker to distinguish between various populations of activated thymocytes. Thymocytes that were selected in Con A + pure or crude IL-2 expressed high 20 alpha SDH activity, while those that were selected in Con A + recombinant IL-1 (rIL-1) or crude IL-1, or Con A + PMA expressed low 20 alpha SDH activity. Both groups proliferate in response to Con A and had IL-2 receptors. After selection, the enzymatic phenotype was stable even if the cells were transferred from Con A + IL-2 to Con A + PMA (or IL-1) or vice versa. A third group was selected from thymocytes that were cultured in PMA + T cell growth factor (TCGF). This group expressed low levels of 20 alpha SDH, had IL-2 receptors, but did not respond to Con A. This paper demonstrates that 20 alpha SDH can be used as an enzymatic marker to distinguish between subpopulations of activated T cells, which have not been previously detected by the conventional surface markers.