Cytokines participate in the induction and effector phases of all immune an
d inflammatory responses. They are therefore obvious candidates for exploit
ation as drugs or drug targets to promote, limit, or alter these responses
in infection, allergy, autoimmunity, and other disease states. Although som
e cytokines and related molecules are already in clinical use, the full the
rapeutic potential of this class of hormones has vet to be realized, and th
is will depend in part on understanding their normal functions and regulati
on in health and disease. An overview is given of the cytokines and their r
eceptors, their genetic and structural relationships, and the regulation of
their activities by naturally occurring antagonists and other physiologic
mechanisms. Some of the ways in which new therapeutic strategies are being
developed from knowledge of the structure, function, and regulation of thes
e various components of the cytokine network are outlined.