HORMONES, PERIPHERALLY ACTIVATED PROHORMONES AND REGULATION OF THE TH1 TH2 BALANCE/

There is much interest in the factors that control the cytokine profil e of T-helper (Th) lymphocytes, and attention has focused on feed-back from the cytokines themselves. In general Th1 cytokines promote Th1 a ctivity and inhibit Th2 activity, and vice versa. Both Th1 and Th2 res ponses should therefore be stable. However, in vivo, many responses st art predominantly as Th1 and then shift to Th2. Why do they do this? A s discussed here, an important influence on this shift that has been l argely ignored in in vitro work is the endocrine system.