Elevated HLA-DR^low CD14⁺ myeloid cells persist in patients with DLBCL after achieving CR and show characteristic features of MDSCs. (A) CD14⁺/HLA-DR^low monocytes were measured by flow cytometry from fresh peripheral whole blood from HCs, patients with DLBCL in CR, when ND, or when R/R. Symbols indicate individual patients, median is indicated. P values determined by the ordinary 1-way analysis of variance (ANOVA) including 2-group comparison using the Šidák multiple comparison when indicated. (B) Time point of individual CD14⁺/HLA-DR^low monocytes shown in panel A. In addition, 27 patients were measured longitudinally and normalized to the first measurement. The red lines indicate linear regression over time including 95% confidence interval (CI) and slope. (C) Rate of CD14⁺/HLA-DR^low cells at CR in subgroups of cell of origin (COO), R-IPI, Ann Arbor stage, age, sex, or tumor bulk, significance determined by the unpaired t test. (D) Intracellular phosphrylated signal transducer and activator of transcription 3 (pSTAT3) by flow cytometry in CD14⁺/HLA-DR^low monocytes compared with HCs, P value determined by ANOVA using the Šidák multiple comparison. (E) Intracellular staining of indoleamine 2,3-dioxygenase 1 (IDO1), arginase-1 (Arg1), and cyclooxygenase 2 (COX2) in CD14⁺/HLA-DR^low and respective DR^high cells of patients with CR, P value determined by the paired t test. (F) Proliferation of activated T cells alone or in coculture with indicated CD14⁺ cell population from n = 15 patients in CR with indicated ratios of myeloid cells to T cells; P values determined by the ordinary 1-way ANOVA. For all panels, ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001. GCB, germinal center B cell; HLA-DR, human leukocyte antigen type DR; MFI, mean fluorescence intensity; ns, not significant.