An in-house Luminex method to analyse if IgG isotypes differ in cases of neonatal alloimmune thrombocytopenia with intracranial haemorrhage

Jayne Johnson, John Aplin, Melissa Westwood, Anthony Poles, Frances Greene

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Neonatal alloimmune thrombocytopenia (NAIT) is a potentially fatal condition that affects the fetus or new-born. Maternally derived IgG alloantibodies directed against paternally inherited specific platelet antigens cross the placenta and target the fetal platelets. The most severe cases result in death due to intra-cranial haemorrhage (ICH) and are mostly due to human platelet antigen (HPA)-1a antibodies. Studies on kidney transplantation have indicated that donor specific HLA antibodies of the IgG4 subtype can predict rejection. This study investigated if IgG subtype analysis could be used to predict ICH in known NAIT cases. Forty samples (20 with and 20 without ICH) were selected from NAIT cases with HPA-1a antibodies detected by the monoclonal antibody immobilisation of platelet antigens (MAIPA). Previous studies using MAIPA have indicated that IgG1 and IgG3 isotypes are present in NAIT but not linked to severity. Here, Luminex technology using an in-house multiplex bead assay with recombinant HPA-1a, HPA-1b and GPVI proteins was tested. Cut-offs were established using One Lambda’s normalised background ratio plus 4SDs from 22 female apheresis donors. Each sample was tested for total IgG and a separate phycoerythrin conjugate for each IgG isotype. Seven samples did not react with the recombinant proteins; two samples were positive for total IgG but negative for all isotypes. Fifteen cases with ICH were positive for total IgG; of these all were positive for IgG1, 5 for IgG2, 5, for IgG3 and 4 for IgG4. Sixteen non-ICH samples were positive for total IgG and 14, 5, 8 and 3 were positive for IgG1, IgG2, IgG3 and IgG4 respectively. This study indicates that there is no difference in IgG isotypes between ICH and non-ICH NAIT cases. Further statistical analysis will analyse ratios with outcomes and compare with different cohorts such as HPA refractory and post transfusion purpura patients.
Original languageEnglish
Title of host publicationHLA
Pages357
Number of pages1
Volume95
Edition4
ISBN (Electronic) https://doi.org/10.1111/tan.13844
Publication statusPublished - 1 Apr 2020

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