Presence of oestrogen receptors in human blood mononuclear cells and thymocytes

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Abstract
We studied oestrogen binding sites in blood mononuclear cells from healthy blood donors, patients with leukaemia or systemic lupus erythematosus, and in thymocytes, using the dextran-coated charcoal assay and Scatchard analysis of binding data. Using 3H-labelled oestradiol as ligand, inaccurate results were obtained which could be related to the low amounts of binding sites. Using 125I-labelled ligand, saturable oestradiol binding sites could be demonstrated in low amount (mean value 2.1 fmol/mg of cytosolic protein) and high affinity (mean Kd value 0.26 nm; mean Ka value 3.85 × 109 m−1). The binding could be inhibited by unlabelled oestradiol but not with oestrone, dihydrotestosterone, cortisol and the progestin-receptor ligand Org 2058. We conclude that blood mononuclear cells and thymocytes contain true oestrogen receptors. This conclusion supports current hypotheses on the involvement of such receptors in oestrogen-mediated modulation of the immune system.