Functional characterization of neutrophils in patients with multiple myeloma.

Multiple myeloma is a hematologic cancer caused by abnormal plasma cell proliferation in the bone marrow and is associated with significant immune dysfunction. Neutrophils, essential components of the innate immune response, may function poorly in patients with multiple myeloma, increasing the risk of infection and affecting disease progression. This study aimed to systematically evaluate the extent of neutrophil dysfunction in patients with newly diagnosed and relapsed multiple myeloma. The study employed a cross-sectional analytical design and recruited 72 participants: 30 multiple myeloma patients and 42 age- and sex-matched healthy controls from the University Teaching Hospital and the Cancer Diseases Hospital of Lusaka, Zambia. 4 mL of venous blood was collected from all participants in ethylenediaminetetraacetic acid vacutainers for laboratory analysis. Neutrophils were isolated from whole blood using Polymorphprep™, and functionality was assessed using in vitro assays, including a phagocytosis assay using fluorescently labeled bacterial particles and a reactive oxygen species assay using the fluorescent probe 2', 7'-Dichlorodihydrofluorescein diacetate, measured by flow cytometry. Statistical analysis was performed using STATA. Neutrophils from multiple myeloma patients demonstrated significantly lower phagocytic capacity (45.0% vs 75.9%, P < 0.001) and reactive oxygen species production (44.7% vs 74.9%, P < 0.001) compared to controls. The logistic regression analysis demonstrated strong associations between multiple myeloma and both reactive oxygen species (OR=5097.6, P < 0.001) and phagocytic dysfunction (OR=7272.7, P < 0.001). By contrast, age, sex, white blood cell count, and absolute neutrophil count were not significantly associated with these outcomes. The study found that patients with multiple myeloma exhibit qualitative impairment of neutrophil function, despite normal quantitative neutrophil counts, underscoring the importance of functional immune monitoring in patient management.