Low-Density Granulocytes Are Decreased in Acute Myeloid Leukemia and in Myelodysplastic Syndromes with Negative Prognostic Factors

Introduction. Myelodysplastic syndromes (MDS), a group of clonal hematological diseases, are characterized by ineffective hematopoiesis, progressive peripheral blood (PB) cytopenia(s), and increased risk of developing acute myeloid leukemia (AML). Classification and risk stratification are constantly under revision for a better estimation of prognosis in those patients. Investigation of immune biomarkers is needed, because immune dysregulation also plays an important role in dysplastic hemopoiesis and immunological escape of neoplastic clones. Here, we studied frequency of low-density granulocytes (LDGs), a neutrophil subset with immunoregulatory functions, in MDS and AML at diagnosis and during treatments. Methods. A total of 17 patients (M/F, 14/12; median age, 69 years old; range, 21-84 years) and seven healthy subjects were enrolled at the Hematology and Transplant Center, University Hospital “San Giovanni di Dio e Ruggi d'Aragona”, Salerno, Italy, between October 2020 and July 2021. Patients were diagnosed with AML (N = 7), or MDS (N = 10) according to the 2016 World Health Organization criteria. For immunophenotyping, fresh EDTA whole PB was stained with the ollowing antibodies: CD45; HLA-DR; CD15; CD3; CD56; CD19; CD11b; CD33; CD34; CD14; and CD16 (all from Beckman Coulter, Brea, CA). Acquisition was carried out using a Navios EX flow cytometer, and Navios software v1.3 (Beckman Coulter). Post-acquisition compensation and analysis were performed using FlowJo software (v.10.7.1, Becton Dickinson). LDGs were identified as CD3-CD56-CD19-CD11b+CD33+CD14-CD15+ cells, following previously published gating strategies (Rahman S, et al. Ann Rheum Dis. 2019). Data were analyzed using Prism (GraphPad software, La Jolla, CA). A P < 0.05 was considered statistically significant. Results. Frequencies of circulating LDGs were significantly reduced in AML patients at diagnosis compared to controls (P = 0.0018) and MDS (P = 0.0077) and were slightly decreased compared to AML in complete remission (P = 0.1605). MDS patients were then divided based on Revised International Prognostic Scoring System (IPSS-R), and very-low and low-risk MDS patients displayed significantly higher circulating LDG frequencies compared to AML at diagnosis (P = 0.0083), while no differences were described between AML at baseline and intermediate-risk MDS (P = 0.1103). Subsequently, LDGs were correlated with clinical and phenotypic features by correlation analysis showing significant negative