Glucocorticosteroid receptors were measured in subpopulations of human peripheral blood T cells identified by the presence of an Fc receptor for IgG (TG) or an Fc receptor for IgM (TM). TM cells are selectively depleted from the circulation by in vivo administration of glucocorticosteroids as opposed to TG cells which are relatively resistant to the lymphodepletive effects of these hormones. However, this selective lymphodepletive effect of glucocorticosteroids on TM cells could not be explained on the basis of detectable differences in intracytoplasmic glucocorticosteroid receptors in these T-cell subpopulations since TG and TM cells had quantitatively similar glucocorticosteroid receptors as well as remarkably similar dexamethasone binding affinities and dissociation constants. Hence, the strikingly different effects of glucocorticosteroids on the circulatory kinetics of TG and TM cells must be explained by mechanisms other than those at the level of the glucocorticosteroid receptor.
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