Regulation of the immune response by polyamines

Regulation of the immune system is accomplished, in part, by numerous soluble factors and small molecules. One such class of regulatory substances may be the polyamines which are present in a variety of tissues. Stimulation of the immune response often occurs by crosslinking of lymphocyte surface proteins, followed by the production of some transmembrane signal. The activation pathway may be interrupted if certain necessary steps are blocked. It is proposed that polyamines exert regulatory influences by modulating crosslink formation; a step catalyzed by the enzyme transglutaminase. A model is outlined which describes the events initiating lymphocyte activation and the role of polyamines in this process. Certain drugs which might mimic the actions of polyamines are also discussed. During evolution of the control of growth processes in cells, relatively simple molecules (the polyamines) may have assumed a pivotal role in initiating and terminating the proliferative response. This idea has been applied to regulation of the immune system.