Properties and regulation of the T lymphocyte insulin receptor.

Primary human T lymphocytes that have been mitogen activated in chemically defined medium express cell surface insulin receptors. The receptor is identical to other mammalian insulin receptors in binding properties, including: pH dependency, ligand affinity, hormone specificity, and cooperative interactions. Scatchard plots are curvilinear and a ligand-induced increase in dissociation, the property normally associated with "negative cooperativity", is kinetically demonstrable. In vitro insulin treatment of the receptor-negative, resting T lymphocyte slightly enhances the degree of insulin binding which emerges following cellular activation. Insulin treatment of receptor-positive lymphoblasts results in insulin receptor "down-regulation". These findings indicate that T lymphoblast insulin receptor concentrations are not significantly influenced by insulin before their emergence but are dramatically regulated by insulin following their appearance at the cell surface.