Hla Typing And Ucb Testing

UCB is HLA typed and subjected to a standard battery of laboratory tests prior to storage. More specific testing for genetic diseases is guided by the donor's history. As a result of the prospective HLA typing and testing, the time required to find a UCB donor and proceed to transplantation is significantly reduced compared to that required for BM sources28 (Table 97.2). HLA typing in preparation for allogeneic transplantation has largely focused on class I (HLA-A and HLA-B) and class II (DRB) antigens. Class I antigens are typed by serologic methods (microlymphocytotoxicity assay), while class II antigens are identified with molecular biology techniques (low-and high-resolution polymerase chain reaction (PCR)). HLA typing of UCB poses certain obstacles, particularly for the serologic assays. Available tissue is often limited due to efforts to maximize the volume of cells available for infusion. The sample size may be inadequate for either initial or repeat typing efforts. In addition, interference with serologic reagents, a high background of dead cells, and contamination of the sample with immature erythroblasts and early myeloid cells may make the results uninterpretable. Given this, recent interest in molecular typing of class I antigens has been generated. A review of 1644 UCB units deemed 14.5% of the serologically HLA-typed class I antigens unsatisfactory due to cross-reactions, false positives, unclear split assessments, or an inability to perform the assay due to poor cell viability.29 Of these unreliable samples 100 were analyzed using molecular biology (PCR) methods, which found that the initial serologic HLA type was incorrectly determined in 56.7% of the units. Nearly 20% could not be typed due to high cell mortality. Similar results were reported in a separate review of over 200 consecutively HLA-typed UCB units.30

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