Mature neutrophil representation at sites of FLs. (A) The mature neutrophils were reclustered and represented using highly variable features. UMAP is plotted in the second and third dimension for visual optimization. Bottom panels represent cell contributions from HBM (left), NDMM (middle), and RRMM (right). (B) UMAP representation of reclustered mature neutrophils observed. In blue, the contribution of cells derived from BM (n = 11 935 cells). In red, the contribution of cells from sites of FLs (n = 23 913 cells). (C) Dot plot depicting the top 8 transcripts from each mature neutrophil cluster. The radius of each circle represents the percentage of cells expressing feature within cluster, and color represents average log₂ fold-change. (D) Schematic of CXCR2⁺ neutrophil developmental trajectories in patients with MM. (E) The fluorescence-activated cell sorter gating strategy involved an initial selection of CD11b⁺ neutrophils and C5AR1⁺ cells, followed by further selection based on CXCR2⁺ and CXCL8⁺ expression. Subsequently, the 3 CXCR2⁺ neutrophil clusters were identified using CD10 and TNFAIP3 gates. The analysis quantified the frequency of these 3 neutrophil subsets sampled from the BM of 3 individual patients. (F) Confocal immunofluorescence images of CXCR2⁺ neutrophils with markers associated with subset features identified in scRNA-seq (right) and CXCR2^– neutrophils with decreased marker expression (right). The data presented in panels E-F are representative of findings from 3 different patients.