[Thrombocyte migration test as a sensitive tolerance test before platelet substitution (proceedings)].

Abstract

Thrombocytopenic patients refractory to random-donor platelet support can usually be substituted by platelets obtained from donors identical with respect to HLA-A and -B antigens [1]. Since such "full-house" identity is rarely available, reliable cross-match tests (CM) are needed in order to pick out donors compatible in spite of HLA non-identity. By use of the thrombocyte migration test (TMT), DUQUESNOY et al. have shown that antiplatelet antibodies may exert an inhibitory effect on platelet migration. Therefore, we have explored this test system for its efficiency as CM compared with the "long-time" lymphocyte cytotoxicity test (LLT). Of 8 sera from polysensitized patients, serial dilutions were performed and simultaneously tested by TMT and LLT with cells obtained from the same control individuals. The sensitivity of TMT exceeded LLT by 2-4 dilution steps in all sera tested. Moreover, 9 patients with incompatible transfusion responses to single-donor platelets in spite of negative LLT had the following results in TMT with pre-transfusion sera: 5 positive (i.e. migration inhibition), 1 negative: enhanced migration was observed 3 times. This phenomenon of enhancement remains to be clarified, since low titers of anti-HLA-antibodies do not cause enhanced platelet migration. Repeated transfusion of platelets obtained from the same donor may cause antibody production against leukocytic antigen not shared by platelets, leading to "false-positive" LLT. 2 patients were successfully substituted with platelets from HLA/MLC-identical siblings in spite of positive LLT, but with negative TMT; in 2 cases with unrelated HLA-A and -B identical donors, TMT results were inconsistent.