The physiology of anti-idiotypic interactions: from clonal to paratopic selection

On theoretical and experimental grounds, it has been proposed that the idiotypes of immunoglobulins and of T cell receptors are composed of multiple paratopes, as opposed to a single paratope and several idiotopes. This necessitates a revision of some of the basic principles of anti-idiotypic reactions. It is also possible to infer the presence of the same or similar paratopes on different idiotypes. A paratope cannot therefore be regarded as restricted to or unique on an idiotype. For these reasons, the perception of immunological specificity in terms of clonal units is misleading. This review proposes instead that the physiological unit of immunological specificity and regulation is the paratope. This essential alteration in the perception of the immune system is referred to as paratopic selection. The approach is assessed in terms of immunological regulation and specificity, and appears to allow new insights into these areas.