The CLEC12A receptor marks human basophils: Potential implications for minimal residual disease detection in acute myeloid leukemia.

BACKGROUND: The transmembrane receptor C-type lectin domain family 12, member A (CLEC12A) is known to be highly expressed on monocytes and neutrophils and is a reliable leukemia associated marker in acute myeloid leukemia. Consequently, detailed knowledge of the various normal cell types expressing this receptor is essential. We have observed CLEC12A to be expressed on CD45lowSSClowCD14-CD123+ basophils in peripheral blood (PB) and in this study, we aimed at verifying this observation and further delineate the CD45lowSSClowCD14-CD123 + CLEC12A+ subpopulation.

METHODS: We analyzed PB from 20 diagnostic chronic myeloid leukemia (CML) samples and eight healthy donors in a six-color multicolor flowcytometry (FCM) based assay. Furthermore, we performed fluorescence activated cell sorting on one CML sample to morphologically confirm the CD45lowSSClowCD14-CD123 + CLEC12A+ subset to be highly enriched for basophils. Finally, to further delineate the CD45lowSSClowCD14-CD123 + CLEC12A+ subpopulation in normal PB, we examined three healthy donors in a 10-color FCM assay enabling further separation of the cell subset into basophils and dendritic cells.

RESULTS: The CLEC12A receptor is expressed on basophils.

CONCLUSIONS: Identification and enumeration of basophils is of high relevance in diagnostic hematology and immunology. We here show that CLEC12A in a simple FCM assay consistently marks basophils. Importantly, as basophils are characterized by a CD45lowSSClow profile similar to the "blast-gate" used for the evaluation of hematological disorders, awareness of minor normal CLEC12A+ subpopulations is crucial when using CLEC12A as a minimal residual disease marker in myeloid malignancies. © 2017 International Clinical Cytometry Society.