1. Institute
of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
2. University of Helsinki and Helsinki University Hospital, Rheumatology, 00029 Helsinki, Finland
3. Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, 00250 Helsinki, Finland
4. Institute of Clinical Medicine, Sognsvannsveien 20, Rikshospitalet, 0372 Oslo, Norway