The effect of HLA allele and haplotype polymorphisms on donor matching in hematopoietic stem cell transplantation - Croatian experience.

The knowledge of HLA characteristics of a patient's population helps to predict the probability of finding a MUD. The study included 170 transplanted patients for whom a search for a MUD in BMDW was performed and a sample of 4000 volunteer unrelated donors from the Croatian Bone Marrow Donor Registry (CBMDR). Patients and their MUDs were typed for HLA-A, -B, -C, -DRB1, and -DQB1 loci using PCR-SSO and PCR-SSP methods while donors were typed for HLA-A, -B, -C, and -DRB1 loci using the PCR-SSO method. A comparison of allele frequencies at tested HLA loci between patients and donors from CBMDR did not reveal significant differences. The majority of patients (117, 68.8%) had a 10/10 MUD, 45 (26.5%) patients had a 9/10 MUD and eight (4.7%) patients had an 8/10 MUD. The highest number of mismatches (MM) was present at HLA-DRB1 (19; 31.1%). The presence of DRB1*11 and DRB1*04 allelic groups among patients caused allelic MMs at HLA-DRB1 in most cases. The presence of an infrequent HLA-B∼C haplotype resulted in the HLA-C MM at antigen level in the majority of cases. The present study clarified HLA factors that cause difficulties in searching for a 10/10 MUD for Croatian patients.