Multifrequency rhythms of immunological functions

Chrono-immunological functions are reviewed starting from the first studies on circadian variations in the count of circulating blood eosinophils to the most recent studies on lymphocyte subpopulation periodicities. Serum Ig levels, complement components, plaque forming cells, phagocytosis, autologous mixed lymphocyte reactions, have also been demonstrated to be circadian periodic. Transplant immunology is also known to show circadian and circa septan periodicities in the rejection of transplanted organs. Rhythms of susceptibility to a series of allergens and bronchial asthma symptoms characterize chronobiology in allergy. A periodic pattern is a common finding in the recurrence of the symptoms in rheumatoid arthritis. Finally, the beginnings of chrono-immunotherapy of experimental and human tumors are briefly reviewed. The conclusion that can be drawn from this short overview is that the demonstration of the periodicity in such a big number of variables in health and the modifications of the relevant parameters in disease, emphasize the importance of the predictable, since periodic, part of the variations that can be shown by the immunological findings.