HLA typing strategies in a cord blood bank

Although widely used, serological typing of HLA loci does not always produce uequivocal results. This may be particularly the case for cord blood since samples may be of small volume and poor quality, and contaminated.

We typed 220 cord blood units (CBU) for HLA class I antigens using the serological technique. For those samples giving doubtful results we repeated the HLA typing by polymerase chain reaction with sequence specific primers (PCR-SSP).

Results were satisfactory for 181 samples (82.3%). For the remaining 39 (17.7%) we had a doubtful antigen assignment for A locus in 9/39 cases (23.1%) and for B locus in 22/39 cases (56.4%). Eight of the 39 samples (20.5%) could not be analyzed by serology due to the high mortality of the cell suspension. Using PCR-SSP we obtained clear definition of class I antigens in all cases. All CBU were typed for HLA class II alleles by PCR-SSP with clear results in 100% of cases.

In our experience, PCR-SSP can resolve the limitations of serology but, at the moment, it cannot substitute the latter in routine practice. The best strategy, in cord blood typing, is to perform both serological and molecular typing in order to obtain an accurate and clear result.