Embryonic mouse thymocyte development. Enhancing effect of corticosterone at physiological levels.

The action of corticosterone on embryonic mouse thymus development has been studied in vitro. Effects of the hormone on lymphoid differentiation varied according to the dose. 0.2-1.0 microgram/ml had an enhancing effect, resulting in an increase in the proportion of Thy-1.2 positive cells as compared with control cultures. Two to fifty micrograms per millilitre had an inhibitory effect, appearing to selectively kill small lymphocytes while leaving large and medium lymphocytes intact. At higher does these immature cells were also killed.