Labeled antigens and antibodies: the evolution of magic markers and magic bullets.

The ability to label antigens and antibodies with simple chemicals and even with whole proteins fostered new approaches to basic studies of the immune system as well as new methods of immunodiagnosis and immunotherapy. This was especially true following the introduction of monoclonal antibodies, which enhanced the specificity of many of these applications. The uses to which these labeled immunoreagents were put were legion, and those who employed them might come from any field of biology or medicine. Many of these technical elaborations were critical to progress in immunology and in many other biomedical sciences. They illustrate also the often complex interplay between technology and theory.