Mechanisms of corticosteroid action on lymphocyte subpopulations. II. Differential effects of in vivo hydrocortisone, prednisone and dexamethasone on in vitro expression of lymphocyte function.

The present study was undertaken to determine what, if any, differential effect various commonly used corticosteroid preparations had on the numbers and specific functions of lymphocyte subpopulations when these agents were administered in equivalent pharmacological dosages. Normal volunteers received a single dose of either 320 mg of hydrocortisone intravenously, 80 mg of prednisone orally, or 12 mg of dexamethasone orally. There was a marked lymphocytopenia and monocytopenia maximal 4-6 hr following administration of all three corticosteroid preparations with almost identical kinetics and degree of fall in total cell numbers as well as proportions of thymus-derived and bone marrow-derived lymphocytes. Hydrocortisone and prednisone caused only a slight suppression of phytohaemagglutiinin (PHA) induced lymphocyte blastogensis which could be reversed at supra-optimal concentrations of PHA. On the contrary, dexamethasone administration casued a marked suppression of PHA responses which was not reversed by supra-optimal PHA stimulation. In addition, hydrocortisone and prednisone administration did not suppress non-specific PHA-induced cellular cytotoxcity, while dexamethasone caused a marked suppression (P less than 0.001) of cytotoxicity. These studies show that although equivalent anti-inflammatory doses of these three corticosteroid preparations cause almost identical suppression of the numbers of circulating lymphocyte populations, they have a differential effect of the numbers of circulating lymphocyte populations, they have a differential effect on a certain in vitro functional correlates of cell-mediated immunity.