Human leukocyte antigen (HLA) antibodies are induced by pregnancy, transfusion, or transplantation. Serum from transplant recipients is regularly screened for IgG HLA antibodies because of their clinical relevance for transplant outcome. While other isotypes of HLA antibodies, such as IgA may also contribute to the alloimmune response, validated detection assays for IgA HLA antibody detection are lacking. Therefore, we modified the commonly used luminex screening assay for IgG HLA antibody detection (IgG‐LMX) into an IgA HLA antibody screening assay (IgA‐LMX). Optimization and validation was performed with IgG, IgA1, and IgA2 isotype variants of HLA‐specific human recombinant monoclonal antibodies (mAbs). Reactivity patterns of IgA1 and IgA2 isotype HLA‐specific mAbs in IgA‐LMX were identical to those of the IgG isotype. Cross‐reactivity with IgG and IgM antibodies and nonspecific binding to the beads were excluded. Further assay validation showed the absence of IgA HLA antibodies in serum from individuals without alloantigen exposure (n = 18). When the IgA‐LMX assay was applied to sera from 289 individuals with known alloantigen exposure through pregnancy (n = 91) or kidney transplantation (n = 198), IgA HLA antibodies were detected in 3.5% of individuals; eight patients on the kidney retransplant waitlist and two women immunized through pregnancy. The majority (90%) of IgA HLA antibodies were directed against HLA class II and were always present in conjunction with IgG HLA antibodies. Results of this study show that this validated IgA‐LMX method can serve as a screening assay for IgA HLA antibodies and that the incidence of IgA HLA antibodies in alloantigen exposed individuals is low.

中文翻译：

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暴露于同种抗原的个体中HLA抗体IgA同型的发生率低

人白细胞抗原（HLA）抗体是通过怀孕，输血或移植诱导的。由于它们与移植结果的临床相关性，因此定期对来自移植受体的血清进行IgG HLA抗体筛查。尽管HLA抗体的其他同种型（例如IgA）也可能促成同种免疫反应，但仍缺乏用于IgA HLA抗体检测的经过验证的检测方法。因此，我们将用于IgG HLA抗体检测（IgG-LMX）的常用luminex筛查方法修改为IgA HLA抗体筛查方法（IgA-LMX）。使用HLA特异性人类重组单克隆抗体（mAb）的IgG，IgA1和IgA2同种型变体进行优化和验证。IgA-LMX中IgA1和IgA2同种型HLA特异性mAb的反应模式与IgG同种型相同。排除了与IgG和IgM抗体的交叉反应以及与小珠的非特异性结合。进一步的测定验证表明，未暴露同种抗原的个体血清中不存在IgA HLA抗体（n = 18）。当将IgA‐LMX分析应用于289名通过怀孕（n = 91）或肾脏移植（n = 198）已知同种抗原暴露的个体的血清时，在3.5％的个体中检测到了IgA HLA抗体。八名接受肾脏再移植等待名单的患者和两名孕妇通过怀孕免疫。IgA HLA抗体的大多数（90％）针对HLA II类，并且始终与IgG HLA抗体一起存在。这项研究的结果表明，这种经过验证的IgA-LMX方法可以用作IgA HLA抗体的筛选测定，并且同种抗原暴露人群中IgA HLA抗体的发生率很低。