Detection of Monocyte Subsets in the Bone Marrow of Patients With Acute Myeloid Leukemia and Its Clinical Significance.

Background: The bone marrow (BM) microenvironment plays a crucial role in acute myeloid leukemia (AML), but the distribution and clinical significance of monocyte subsets within this compartment remain poorly characterized. This study aimed to investigate the composition of BM monocyte subpopulations and their relationship with systemic immunity and clinical outcomes in AML patients. Methods: We collected BM samples from 98 AML patients (including 23 newly diagnosed, 28 nonremission, and 47 complete remission [CR] cases) and 23 healthy controls (HCs). Using flow cytometry, we analyzed monocyte subsets (classical, intermediate, nonclassical) and monocytic myeloid-derived suppressor cells (m-MDSCs) in BM, along with T lymphocyte subsets in peripheral blood. Survival analysis was performed with 1-year follow-up data. Results: Both the proportion of intermediate monocytes and m-MDSCs among total monocytes were significantly elevated in newly diagnosed AML patients compared to those in HCs (p  = 0.019 and p  = 0.003, respectively) and CR (p = 0.003 and p = 0.037, respectively). This elevation was followed by a gradual decrease from diagnosis to remission. Multivariate Cox regression identified intermediate monocyte percentage as an independent prognostic factor (HR = 4.170, p = 0.034). Kaplan-Meier analysis confirmed that higher intermediate monocyte levels predicted shorter overall survival (OS) (p = 0.031) and leukemia-free survival (LFS) (p = 0.028). Importantly, negative correlations were observed between BM blasts and peripheral blood T-cell percentage (r = -0.467, p = 0.005) and CD8+ T cells (r = -0.504, p = 0.002), and between intermediate monocytes among total monocytes and total T-cell percentage (r = -0.475, p = 0.004). Conclusions: BM monocyte subsets, particularly intermediate monocytes, serve as significant indicators of disease progression and survival in AML. Their correlation with peripheral T-cell immunity suggests their potential role in modulating antileukemic immune responses. These findings highlight the prognostic value of BM monocyte profiling and provide insights for developing novel immunotherapeutic strategies in AML.