PT - JOURNAL ARTICLE AU - Howie, Heather L AU - Wang, Xiaohong AU - Kapp, Linda AU - Lebedev, Jenna N AU - Zimring, James C TI - Identification of IgG3-specific epitope that remedies problem in diagnostic IgG subclass determination due to human genetic variation AID - 10.1136/jclinpath-2018-205001 DP - 2018 Jun 01 TA - Journal of Clinical Pathology PG - 559--561 VI - 71 IP - 6 4099 - http://jcp.bmj.com/content/71/6/559.short 4100 - http://jcp.bmj.com/content/71/6/559.full SO - J Clin Pathol2018 Jun 01; 71 AB - There are four subtypes of human IgG with different effector functions. Quantifying the relative amount of each IgG subtype is important for laboratory diagnosis in multiple settings. However, in an evolving landscape of the appreciation of human variability and the need for precision/personalised laboratory diagnosis, it has also been shown that there are numerous natural variants of IgG subtypes, with at least 29 having been described. It has recently been reported that commercially available polyclonal antisera to IgG3 cross react with variants of other IgG subtypes, while available monoclonal anti-IgG3 have a blind-spot for the IgG3-04 variant. Herein, we report that IgG3-04 contains an epitope in common with all known IgG3 variants and absent in other subtypes. A novel monoclonal anti-IgG3 is described that is specific to IgG3 but without any blind-spots for known IgG3 variants, providing a remedy to the problem of genetic variability of IgG3.