Division of Hematology, Alberta Public Laboratories & Department of Pathology & Laboratory Medicine, University of Calgary, Calgary, Alberta, Canada.
Cytometry B Clin Cytom. 2020 Jan;98(1):68-74. doi: 10.1002/cyto.b.21837. Epub 2019 Jul 17.
Daratumumab (DARA) is a humanized Immunoglobulin G(IgG)1-kappa monoclonal antibody against CD38 antigen that is shown to improve outcomes in relapsed/refractory plasma cell myeloma (PCM) patients. Since CD38 is expressed by different hematopoietic elements, DARA has the potential to interfere with flow cytometric assessment of bone marrow specimens.
Flow cytometric analysis of bone marrow samples from 10 PCM on DARA and 5 control samples was performed using two different antibody panels.
Bone marrow samples from PCM patients on DARA exhibited a population of CD19+ CD10+ B-lymphoid cells with kappa light chain restriction. Further morphological and immunophenotypic studies suggested that this population represents marrow hematogones. Marrow hematogones from control samples showed normal immunophenotypic profiles.
DARA on the surface of hematogones interferes with flow cytometric clonality study leading to artifactual kappa light chain restriction, which can result in false interpretation of a concurrent clonal B-cell proliferation. In the era of rapidly growing list of therapeutic monoclonal antibodies, flow cytometry pathologists should be aware of potential interferences to avoid misdiagnosis. © 2019 International Clinical Cytometry Society.
达雷妥尤单抗（DARA）是一种针对 CD38 抗原的人源化 IgG1-κ 单克隆抗体，已被证明可改善复发/难治性浆细胞骨髓瘤（PCM）患者的预后。由于 CD38 表达于不同的造血细胞，DARA 可能会干扰骨髓标本的流式细胞术评估。
使用两种不同的抗体组合对 10 例接受 DARA 治疗的 PCM 患者和 5 例对照患者的骨髓样本进行流式细胞术分析。
接受 DARA 治疗的 PCM 患者的骨髓样本中存在一群 CD19+ CD10+ B 淋巴细胞，具有κ轻链限制性。进一步的形态学和免疫表型研究表明，这群细胞代表骨髓造血前体细胞。对照样本的骨髓造血前体细胞显示出正常的免疫表型特征。
DARA 表面的造血前体细胞会干扰流式细胞术克隆性研究，导致虚假的κ轻链限制性，从而可能导致对同时存在的克隆性 B 细胞增殖的错误解读。在治疗性单克隆抗体数量迅速增加的时代，流式细胞术病理学家应意识到潜在的干扰，以避免误诊。© 2019 年国际临床细胞化学学会。
