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Purpose: Natural killer (NK) cells are traditionally identified by flow cytometry using a combination of markers (CD16/CD56/CD3), because a specific NK-cell marker is still missing. Here we investigated the utility of CD314, CD335 and NKp80, compared to CD16/CD56/CD3, for more robust identification of NK-cells in human blood, for diagnostic purposes. Methods: A total of 156 peripheral blood (PB) samples collected from healthy donors (HD) and patients with diseases frequently associated with loss/ downregulation of classical NK-cell markers were immunophenotyped following EuroFlow protocols, aimed at comparing the staining profile of total blood NK-cells for CD314, CD335 and NKp80, and the performance of distinct marker combinations for their accurate identification. Results: NKp80 showed a superior performance (vs. CD314 and CD335) for the identification of NK-cells in HD blood. Besides, NKp80 improved the conventional CD16/CD56/CD3-based strategy to identify PB NK-cells in HD and reactive processes, particularly when combined with CD16 for further accurate NK-cell-subsetting. Although NKp80+CD16 improved the identification of clonal/tumor NK-cells, particularly among CD56- cases (53%), aberrant downregulation of NKp80 was observed in 25% of patients, in whom CD56 was useful as a complementary NK-cell marker. As NKp80 is also expressed on T-cells, we noted increased numbers of NKp80+ cytotoxic T-cells at the more advanced maturation stages, mostly in adults. Conclusion: Here we propose a new robust approach for the identification of PB NK-cells, based on the combination of NKp80 plus CD16. However, in chronic lymphoproliferative disorders of NK-cells, addition of CD56 is recommended to identify clonal NK-cells, due to their frequent aberrant NKp80- phenotype. [ABSTRACT FROM AUTHOR]

In contrast to the majority of αβ peripheral T cell lymphomas (PTCL), which usually originate in lymph nodes and do not express NK-associated molecules, most γδ PTCL express a cytotoxic phenotype and originate at extranodal sites. We report a case of a patient with a gamma-delta PTCL who presented with large mandibular and parotidal lymphadenopathy and skin lesions. CD3(+)/TCR-Vδ1(+) lymphoma cells did not express the cell surface (CD11b, CD11c, CD16, CD56 and CD57) and cytoplasmic granule molecules (Perforin and Granzyme B) that usually characterize the cytotoxic T-cells, a phenotype that fulfils the criteria for diagnosis of a rare non-cytotoxic variant of a γδ T-cell lymphoma. "In situ" hybridization for Epstein-Barr virus-encoded RNA and latent membrane protein-1 gave negative results. The disease had an aggressive course and was resistant to chemotherapy and the patient died 4 months after diagnosis. [ABSTRACT FROM AUTHOR]