RHYTHMS IN THE IMMUNE-SYSTEM

This report reviews the evidence that cells within the immune system a re subject to rhythmic influences that affect numbers of circulating c ells and their function both in vitro and in vivo. It is concluded tha t, although periodicity has clearly been demonstrated for numbers of i mmunocompetent cells in the circulation, significant functional change s have not been consistently observed. A number of neuroendocrine horm ones, which modulate immune responsiveness in vitro and which are rele ased in a rhythmic manner, are considered as mediators of the observed effects on the immune system and this is related to changes in expres sion and activity of immune-mediated diseases such as rheumatoid arthr itis.