- Two Suitable Umbilical Cord Blood Units: a cryopreserved dose of at least 1.5 x 107 TNC/kg. If the unit contains red cells at time of cryopreservation, the cryopreserved dose must be at least 2.0 x 107 TNC/kg. Each unit must be at least 4/6 HLA-A and B antigen, and DRB1 allele matched with the recipient. Each unit must be at least 3/6 HLA-A, B DRB1 antigen matched to each other.