Cystatins comprise a large superfamily of related proteins with diverse biological activities. They were initially characterised as inhibitors of lysosomal cysteine proteases, however, in recent years some alternative functions for cystatins have been proposed. Cystatins possessing inhibitory function are members of three families, family I (stefins), family II (cystatins) and family III (kinin...

The components and functions of the immune system are described, and the clinical applications of agents that affect the immune system are discussed. Through both nonspecific and specific responses, the immune system recognizes and destroys or eliminates harmful foreign substances with which a host comes into contact. Nonspecific responses are usually associated with the first introduction of a...