- Availability of donor cord blood (one to three units) matching at > or equal to 4 of 6 HLA antigens (A, B, and DR). HLA class I antigens will be determined by serologic methods, and Class II antigens will be determined by high-resolution DNA typing. Typing will be confirmed by the UCSF Immunogenetics Department. The target UCB TNC dose is > or equal to 3.5 x 10(7) TNC/kg recipient weight, however the absolute minimum TNC requirement is > 2.5 x 10(7) TNC per kilogram) based on cell counts prior to cryopreservation. Cord blood units will be obtained from all available international banks.