1. Department of Pathology, Abbott Laboratories, North Chicago, Illinois, U.S.A.
2. Department of Pathology, Abbott Laboratories, North Chicago, Illinois, U.S.A.; Present address: Department of Pathology, University of Chicago, Chicago, Illinois, U.S.A.
3. Department of Pathology, Abbott Laboratories, North Chicago, Illinois, U.S.A.; Present address: McHenry Medical Group, 1110 Green Street, McHenry, Illinois, U.S.A.