PERSISTING VIRUSES AND CHRONIC INFLAMMATION - UNDERSTANDING THEIR RELATION TO AUTOIMMUNITY

Viral infections may induce and sustain autoimmune processes via sever al and overlapping mechanisms. We outline how chronic inflammation, su stained by persisting viruses, may be ''the prerequisite'' for initiat ion and maintenance of the multistep process leading to autoimmunity C hronic inflammation may favour priming of autoreactive T cells which h ave escaped thymic tolerance and are able to mount a cross-reactive re sponse to self-mimicking antigens carried by viruses in the periphery. Moreover, chronic inflammation and persisting viruses can synergistic ally support autoimmunity through other relevant mechanisms: unveiling of cryptic self-epitopes, determinant spreading, activation of dendri tic cells, constant priming of new autoreactive T cells, and efficient generation and restimulation of memory cells. Therefore, viruses seem to play a key role among the many environmental factors which, togeth er with the genetic background, have been implicated in the pathogenes is of autoimmune diseases. We will also discuss some hypotheses explai ning why autoimmunity is a rare event.