[1] UNIV BASEL,INST MED MICROBIOL,CH-4051 BASEL,SWITZERLAND
[2] UNIV HOSP ZURICH,INST PATHOL,CH-8091 ZURICH,SWITZERLAND
[3] BASEL INST IMMUNOL,CH-4005 BASEL,SWITZERLAND
[4] UNIV BERN,INST PATHOL,CH-3000 BERN,SWITZERLAND
[5] UNIV ZURICH,DEPT ANAT,CH-8050 ZURICH,SWITZERLAND