Hardly a decade ago, membrane receptors were an attractive but largely
unproven concept. Since that time enormous progress has been made, and
we are now able to consider receptors much more concretely. Their
existence has been established, their binding properties have been
determined, and in some cases, they have been highly purified and their
physical-chemical properties studied. It is now even possible to
visualize microscopically some receptors. This progress has resulted
largely from the development of highly powerful methods. These methods
are the subject of this volume. Although considerably diverse, different
receptors share certain common pro- perties, and common problems are
encountered in their study. Consequently, a small number of techniques
are particularly useful in studying different types of receptors. Thus,
it makes sense to speak about membrane receptor methodology. A very
apparent problem in the study of membrane receptors is their presence in
exceedingly small quantities and in a highly impure state. Therefore,
very sensitive and specific techniques are required for their detection,
characterization and purification. Such sensitivity and specificity is
provided by the ability of receptors to bind certain ligands with very
high affmity, and it is not surprising that most of the methods
described in this volume depend upon this high affinity binding. The
antigen-antibody interaction is of comparable sensitivity and speci-
ficity. Recently, a number of anti-receptor antibodies have been
produced or found to occur spontaneously in auto-immune diseases.
Undoubtedly, more will be produced in the future.
