title: Characterisation of maternal human leukocyte antigen class I antibodies in suspected foetal and neonatal alloimmune thrombocytopenia.
abstract: OBJECTIVE
  To investigate the specificities and level of HLA class I antibodies in selected cases referred for suspected foetal and neonatal alloimmune thrombocytopenia (FNAIT).
  
  
  BACKGROUND
  FNAIT occurs in 1 : 1-2000 live births, whereas maternal immunisation against human leukocyte antigen (HLA) class I is common. Whether HLA class I antibodies alone can cause FNAIT is debatable.
  
  
  METHODS
  A total of 260 patient samples were referred between 2007 and 2012. Referrals with maternal HLA class I antibodies and no other cause for the neonatal thrombocytopenia were included for analysis (cases, n = 23). HPA-1a negative mothers were excluded. Control groups were screened positive mothers of healthy neonates (controls, n = 33) and female blood donors (blood donors, n = 19). LABScreen single antigen HLA class I beads was used for antibody analysis. Clinical records were reviewed for cases.
  
  
  RESULTS
  All groups had broad antibody reactivity. Cases had more antibodies with high SFI levels compared with the controls (SFI>9999; medians 26, 6 and 0; P < 0·05) and higher overall median HLA-ABC and HLA-B SFI (P < 0·05). Many of the antibodies were reactive with rare alleles. When reviewing the clinical records, several of the cases had other contributing factors to the thrombocytopenia. There was no correlation between foetal platelet count and antibody levels.
  
  
  CONCLUSIONS
  Mothers of thrombocytopenic neonates had higher levels of HLA class I antibodies compared with control groups of women with healthy children and female blood donors. However, clinical outcome and antibody response correlated poorly in the heterogeneous case group, indicating a multifactorial cause to the thrombocytopenia in the majority of cases.
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Refsum
authors.affiliation: Department of Clinical Immunology and Transfusion Medicine, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Mörtberg
authors.affiliation: Department of Medical Biology, Immunology Research Group, Arctic University of Norway, Tromso, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Dahl
authors.affiliation: Department of Medicine Huddinge, Center for Hematology and Regenerative Medicine (HERM), Karolinska Institutet, Stockholm, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Meinke
authors.affiliation: Department of Clinical Immunology and Transfusion Medicine, Karolinska University Hospital, Stockholm, Sweden.|Advanced Medical and Dental Institute, Universiti Sains Malaysia, George Town, Malaysia.
authors.forename: M-K
authors.initials: MK
authors.lastname: Auvinen
authors.affiliation: Department of Obstetrics and Gynaecology, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Westgren
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Reilly
authors.affiliation: Department of Clinical Immunology and Transfusion Medicine, Karolinska University Hospital, Stockholm, Sweden.|Department of Medicine Huddinge, Center for Hematology and Regenerative Medicine (HERM), Karolinska Institutet, Stockholm, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Höglund
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.|Department of Clinical Immunology and Transfusion Medicine, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Wikman
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D005260:Female; D005331:Fetomaternal Transfusion / Q000097:blood* / Q000150:complications; D015395:Histocompatibility Antigens Class I; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D054098:Thrombocytopenia, Neonatal Alloimmune / Q000097:blood* / Q000209:etiology
chemical_list: D001323:Autoantibodies; D015395:Histocompatibility Antigens Class I
keywords: Luminex; foetal and neonatal alloimmune thrombocytopenia; human leukocyte antigen; neonatal thrombocytopenia