Alloimmunization against human platelet antigens (HPAs) during pregnancy is rare but can lead to severe bleeding disorders, such as fetal and neonatal alloimmune thrombocytopenia.STUDY DESIGN AND METHODS:
In a cohort of 241 uncomplicated pregnancies, we investigated the immunogenicity of HPA mismatches and correlated HLA sensitization with HPA antibody formation. HPA antibodies were measured with a Luminex-based multiplex assay.RESULTS:
HPA mismatches were observed in 109 of 241 pregnancies (45%), but child-specific HPA antibodies were only found in two of 109 cases (2%), indicating a low immunogenicity. Only nine of 241 women (4%) had detectable HPA antibodies. HLA sensitization was identified as a strong and independent predictor for HPA antibody formation (hazard ratio, 10.2; 95% confidence interval, 1.8-193; p = 0.006), whereas the number of pregnancies was not.CONCLUSION:
Our observational data indicated a low immunogenicity of HPA and suggest that a broader immune response—inferred by HLA sensitization—is probably associated with HPA antibody induction.