Distribution of concanavalin-A receptor sites on the surface of human resting T lymphocytes. A stereological study using concanavalin-A/colloidal-gold-labelled horseradish peroxidase.

Stereologic techniques were used to analyse the density and distribution of Concanavalin-A (Con-A) receptor sites on the surface of isolated resting human peripheral-blood T lymphocytes using Con-A/colloidal-gold-labelled horseradish peroxidase. The T-lymphocyte surface appeared to be composed of microvilli, smooth areas and uncoated pits. Coated pits and coated vesicles, identified by the preferential staining of clathrin-containing membranes (tannic-acid/saponin fixation), were scarce. Quantitative analysis of the gold labelling on T lymphocytes after glutaraldehyde fixation indicated the presence of 2.13 +/- 0.46 gold particles per micron of cell surface and that these particles were preferentially located on uncoated pits. These results suggest the existence of cell-surface domains for these receptor sites in human resting T lymphocytes.