Neonatal alloimmune thrombocytopenia caused by human leucocyte antigen-B27 antibody.

Neonatal alloimmune thrombocytopenia (NAIT) occurs when maternal alloantibodies to antigens presented on foetal platelets cause their immune destruction. Whether human leucocyte antigen (HLA) antibodies can cause NAIT is controversial. Here, a patient was described who suffered from a NAIT caused by an HLA-B27 antibody. Sera from the mother and the newborn were tested for human platelet antigen antibodies and HLA antibodies by monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay, solid phase-linked immunosorbent assay (ELISA), lymphocytotoxicity assay (LCT) and flow cytometric analysis. No antibodies against cluster designation (CD)109 and platelet glycoproteins of the father were found in patient's and mother's serum. However, HLA ELISA was used to identify HLA antibody in both sera. The antibody was specified as HLA-B27 antibody. Typing results showed that the father descended HLA-B27 antigen on patient and his brother. The mother was HLA-B27 negative. It is most conceivable that the previous pregnancy of the mother induced the production of anti-HLA-B27 antibody, which crossed the placenta and subsequently caused an NAIT in the case presented.