The immunogenicity of Gov alloantigens is comparable to that of the HPA-5 system

Abstract

The 175 kDa glycosylphosphatidylinositol (GPI)-linked glycoprotein CD109 carries the bi-allelic platelet system, Gov. To date, detection of Gov antibodies has relied on the immunoprecipitation of radio-labelled CD109. We have modified the monoclonal antibody-specific immobilization of platelet antigen assay for the detection of Gov antibodies. Screening of 605 archived patient samples referred for neonatal alloimmune thrombocytopenia (NAITP, n = 305); post-transfusion purpura (PTP, n = 60); and platelet refractoriness (PR, n = 240) revealed 14 Gov antibodies (10 anti-Gova, 4 anti-Govb) which equals the number of HPA-5 antibodies detected in the 605 samples. There is no obvious linkage between the HLA class II type and the ability to mount an immune response. Phenotyping of 113 donors by MAIPA showed frequencies of 19·5%, 40·7% and 39·8% for ‘aa, ab and bb’, respectively, with ‘a’ and ‘b’ allele frequencies of 0·40 and 0·60. Cloning of the CD109 gene and determination of the molecular basis of the Gov antigens has become relevant now that it has been established that Gov alloantibodies are more frequent than previously thought.