Factors responsible for successful HLA-DR typing of mononuclear cells from cord blood

Of 115 cord blood samples tested, both HLA-DR antigens were identified in 79% of fresh samples, 66% of older samples and 55% of freshly frozen samples. Because of weak reactions, one or two questionable antigens were present in 21% of fresh samples as compared to 34% of older samples and 45% of freshly frozen samples. Older samples showed lower cell viability, more extra reactions, and a high frequency of weak reactions. Comparison of cord blood DR antigens with parental DR antigens revealed that antigens were missed or inappropriately assigned in 5 known cases. This was more frequent with older blood samples. The critical factors in successful DR typing of cord blood samples were 1) dilution of cord blood samples with medium, 2) processing of the samples as soon as possible, and 3) overnight incubation to remove adherent cells.