Receptors: the materialization of a concept.

The evolution of the receptor concept over the years, culminating in the materialization thereof is outlined step by step. Attention is paid to molecular pharmacology, affinity and intrinsic activity, partial agonists and partial antagonists, receptor differentiation, receptor kinetics, receptor dynamics, receptor-effector coupling and receptor reserve, localization, quantification and isolation of receptors. Receptor pathology includes 'inborn errors of receptor function', involvement of receptors in autoimmune diseases and in malignant diseases. Finally iatrogenic receptor imbalances are discussed.