Jerne put forth a hypothesis in 1974 that has intrigued immunologists for more than a decade. 1 He proposed that the immune response might be regulated via the unique antigenic determinants of immunoglobulin variable regions (idiotypes, Id) described earlier by Kunkel 2 and Oudin. 3 The Id determinants of each antibody molecule would be complemented by those of another, allowing protein interactions between antibody molecules, creating an Id network through which immunoglobulin expression might be controlled. A multitude of experiments followed in which manipulation of the immune response was achieved through the use of anti-idiotypic (anti-Id) reagents. 4 These studies have generally strengthened his hypothesis.