- Availability of donor cord blood (one to three units) matching at least 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 UCSF Immunogenetics Department following infusion. The UCB units must contain >2.5 x 10(7) TNC per kilogram recipient body weight. Cord blood units will be obtained from all available international banks.