NEONATAL ALLOIMMUNE THROMBOCYTOPENIA IN TAIWAN DUE TO AN ANTIBODY AGAINST A LABILE COMPONENT OF HPA-3A (BAK(A))

We report on two siblings who developed severe neonatal alloimmune thr ombocytopenia (NAIT) due to an alloantibody against a labile component or components of the HPA-3a (Bak(a)) antigen. The antibody reacted on ly with fresh, unfixed platelets by the solid-phase red cell adherence test, immunofluorescence test and mixed passive haemagglutination tes t, In the latter method: weakly fixed platelets also gave a weak posit ive reaction, Monoclonal-antibody-specific immobilization of platelet antigens and immunoblotting tests gave negative results, Our findings may possibly help to explain why in some cases of NAIT no platelet-spe cific antibody is demonstrable in tests with fixed or solubilized plat elets,