Paul Ehrlich's passion: the origins of his receptor immunology

In 1897, Paul Ehrlich published a selection theory of antibody formation that anticipated the theories of Jerne and Burnet by some 60 years. Ehrlich introduced into immunology the concept of the interaction of physiologically active substances with specific receptors, an idea that still dominates modern immunological thought. In this paper, we point out how Ehrlich's concept matured over 20 years, while it governed his studies in histological staining, in cell physiology, in hematology, and finally in his major contributions in experimental immunology.