HPA-alloimmunization is a major factor in refractoriness to HLA-matched platelet transfusion. Retrospective studies indicate that although HPA-matched platelet transfusion is effective in such cases, it is extremely difficult to deal with such situations prospectively. We report a case of successful transfusion of HPA-matched platelets selected by HPA-DNA typing with frozen lymphocytes of HLA-matched donors. The patient was a 51-year-old male with CML who developed HLA antibodies after multiple trnasfusion of random platelets. However, HLA-matched platelets were ineffective. Further serological tests including monoclonal antibody-specific immobilization of platelet antigens (MAIPA) revealed that he also possessed HPA-3a antibody, which appeared to be responsible for the refractoriness. HPA-DNA typing by the PCR-SSP method indicated that his HPA-3 type was b/b and those of refractory donors were HPA-3a/a or HPA-3a/b. By HPA-3 typing with 122 frozen lymphocytes of HLA-matched donors, 14 donors were found to be HPA-3b/b. HLA-HPA matched platelets from these donors were shown to be effective, indicating that refractoriness in this patient was due to HPA-3a-alloimmunization. The method described here for selection of HLA-HPA matched donors is effective under the following circumstances: 1) a considerable number of HLA-matched donors and their frozen lymphocytes are available; 2) HPA matching frequency of a given case is not rare; and 3) transfusion of matched platelets is expected to be terminated in a limited period.
