1. Department of BiochemistryMerck Sharp and Dohme Research LaboratoriesRahwayNew Jersey07065USA
2. Department of ImmunologyScripps Clinic and Research FoundationLa JollaCalifornia92037USA
3. Laboratory of Cellular Physiology and ImmunologyThe Rockefeller UniversityNew YorkNew York10021USA
4. Department of GeneticsUniversity of WashingtonSeattleWashington98195USA
5. Department of MedicineCornell University Medical CollegeNew YorkNew York10021USA