JAKS, STATS AND THE IMMUNE-SYSTEM

Changes in gene expression are necessary for an adaptive response of c ells to immunological stimuli and thus for their proper function in th e concert of the immune system. Regulatory inputs usually originate fr om cell surface receptors and in many cases affect the transcription r ates of specific genes by modulating the activity of transcription fac tors. The Jak-Stat signalling paradigm has received large attention by molecular immunologists because it applies to nuclear signalling by a ll cytokine receptors. In its simplest form it requires only two prote in components downstream of the receptor: Janus family protein tyrosin e kinases (Jaks) which are usually receptor-associated, and signal tra nsducer and activator of transcription (Stat) family transcription fac tors which carry the receptor-generated signal to the nucleus and stim ulate gene expression. Here we give a brief overview of both recent pr ogress and open questions concerning the Jak and Stat molecules, their regulation, and the biological implications of their activity.