There are conflicting data concerning the value of selecting an allelic mismatch over an antigenic mismatch. Petersdorf et al did not find any apparent difference between allele and antigen mismatches with respect to the number of deaths from transplant, suggesting that donors with a single HLA allele antigen mismatch may be used for hematopoietic stem cell transplantation when a fully matched unrelated donor is not available for patients with severe diseases not permitting time for lengthy search. There were no significant differences in survival depending on whether the mismatch was allelic or antigenic mismatch at HLA-C. However, Flomenberg et al found that antigenic mismatch was associated with higher mortality compared to allelic mismatch . They indicated that selection of donors with high-resolution mismatches over those with low-resolution mismatches may lower the rate of post transplant complication.