Beta-Adrenergic Receptors are Different in Subpopulations of Human Circulating Lymphocytes

Abstract

Mononuclear leucocytes (MNL) were isolated from blood of 11 healthy blood donors. Lymphocyte subsets were sorted in a Cytofluorograf after direct (B cells) or indirect immunofluorescence labeling with monoclonal antibodies directed against the phenotypes of T -, T helper (Th) - and T suppressor (Ts) cells. The sorted cells were incubated with (±)¹²⁵iodocyanopindolol ([¹²⁵I]CYP) for the determination of beta-adrenergic receptors. Beta-adrenergic receptors on B cells were increased two-fold (3700 sites/cell, p<0.004) and had a lower affinity (dissociation constant K_D 40pM, p<0.03) when compared with T cells (1400 sites/cell, K_D 17pM). Receptors on Th- and Ts cells showed a similar binding capacity, but Ts cells had a slightly higher [¹²⁵I]CYP binding affinity (K_D 13 pM) than Th cells (K_D 27 pM, p<0.02). The different densities and affinities of beta-adrenergic receptors in human lymphocyte subsets, as assessed by antagonist binding should be considered in the interpretation of receptor alterations of unfractionated MNL, which may occur simultaneously to changes of the blood leucocyte distribution.