We have read with interest the letter to editor by M. Roelens et al. in response to our article on Sézary syndrome (SS) and mycosis fungoides (MF) and the role of immunophenotyping for diagnosis. We appreciate their comments on the potential utility of CD158k (KIR3DL2) for the diagnosis of SS and MF, which certainly complement the data on SS immunophenotyping we report. The authors cite their published work about the role of CD158k for the precise identification of Sézary cells (SCs). Based on their observations, they recommend introducing KIR3DL2/CD158k as a positive marker for the accurate identification of SCs using flow cytometry (Roelens, de Masson, Ram‐Wolff, Bagot, & Moins‐Teisserenc, 2020). We agree that CD158k is a promising marker, particularly because it would allow “positive” selection of SCs (instead of focusing on downregulated molecules, such as CD7 and CD26) while being negative in normal residual CD4+ T cells, as stated by Roelens et al. However, it should be noted that unequivocal expression of CD158k on SCs from most SS cases has been reported only by this group (though consistently over a long time), using an antibody obtained from a therapeutic antibody manufacturer and not commercially available as a flow‐cytometry reagent. Unfortunately, other authors could not reproduce these results using the same clones and fluorochrome (Boonk et al., 2016, and personal observations), possibly due to issues with the reagent, such as lot‐to‐lot variability and stability for a product that most likely does not currently meet the quality standards to be sold as an analyte specific reagent (ASR) or even a research use only (RUO) antibody. Therefore, to definitively establish the precise utility of CD158k for SS (and MF) immunophenotyping in a standardized way, the exact antibody products used by M. Roelens et al (i.e., clone AZ158k or more recently clone 13E4, both conjugated to phycoerythrin, provided by Innate Pharma, Marseille, France) should be used and offered as a standard quality flow cytometry product (i.e., guaranteeing lot‐to‐lot stability, effective and stable dye‐to‐antibody ratio, etc.) available for purchase. This would allow different groups of experts to reach reproducible and comparable results, before recommending the systematic inclusion of CD158k in consensus/standardized panels for SS/MF immunophenotyping.

我们感兴趣地阅读了M. Roelens等人写给编辑的信。为了回应我们有关塞扎利综合症（SS）和蕈样真菌病（MF）以及免疫表型在诊断中的作用的文章。我们赞赏他们对CD158k（KIR3DL2）在SS和MF诊断中的潜在效用的评论，这些评论无疑补充了我们报告的SS免疫表型的数据。作者引用了他们发表的有关CD158k在精确鉴定Sézary细胞（SCs）中的作用的工作。根据他们的观察，他们建议引入KIR3DL2 / CD158k作为使用流式细胞仪准确鉴定SC的阳性标记物（Roelens，de Masson，Ram-Wolff，Bagot和Moins-Teisserenc，2020年））。我们同意CD158k是一个有前途的标记，特别是因为它可以允许SC的“阳性”选择（而不是专注于下调的分子，例如CD7和CD26），而在正常的残留CD4 + T细胞中却是阴性的，如Roelens等人所述。 。但是，应该注意的是，大多数SS病例仅在该病例中报告了CD158k在SC上的明确表达（尽管长期以来一直如此），使用的是从治疗性抗体制造商那里获得的抗体，但不能以流通方式从市场上买到。细胞计数试剂。不幸的是，其他作者无法使用相同的克隆和荧光染料重现这些结果（Boonk等人，2016和个人观察），可能是由于试剂问题所致，例如批次之间的差异和稳定性，这些产品目前极有可能不符合作为分析物专用试剂（ASR）甚至是待售产品的质量标准仅研究用（RUO）抗体。因此，为了以标准化的方式确定性地建立CD158k在SS（和MF）免疫表型分析中的精确效用，提供了M. Roelens等人使用的确切抗体产品（即克隆了AZ158k或更近的克隆13E4，它们都与藻红蛋白缀合）应使用法国马赛的Innate Pharma公司提供的标准质量流式细胞仪产品（即保证批间稳定性，有效的染料和抗体比例等），以供购买。