1. Institute of Immunology-Vienna International Research Cooperation Center at SFI, University of Vienna, Brunner Strasse 59, A-1235 Vienna, Austria.
2. Institute of Molecular Genetics, Czechoslovak Academy of Sciences, 142 20 Prague 4, Vídeňská 1083, Czechoslovakia.
3. Department of Immunology, Karolinska Institute, S-104 01 Stockholm, Sweden.