- In fact, choosing 217 patients who had a need for transplantation, the percentage of patients who found umbilical cord blood stem cell units had a sufficient number of total nucleated cell, CD34 cells and match with the three main locus (A, B, DR) of HLA at the levels: 4/6 is 96.8%; 6/6 is 69.6%; 6/6 is 18%.