Mass cytometry (CyTOF) analysis of PBMC samples from untreated patients with CMML and age-matched normal PBMC controls. (A) Heatmap of all the markers used in the CyTOF panel (details in supplemental Table 3) and stratified by a representative sample in each group (normal control [NC], CMML without BM IDC aggregates, and CMML with BM IDC). Expression is indicated as transformed ratio of means. (B) Tregs, calculated as median value of percentage (%) of parent cell type (CD4 T), did not significantly (ns) differ between CMML cases and controls (8.5 vs 5.5; P = .4). (C-D) Significantly suppressed median percentage (%) of parent cell aggregates of Th1 (median, 4.04 vs 27.2; **P = .003) and CD4 terminal effector (te) cells (11.6 vs 38.7; *P = .02). (E) An expanded NK (2.6 vs 1.1; *P = .02) cell population in CMML vs normal controls. (F) Visualization of dimensionality reduction analysis plot with gates delineating CD4⁺, CD8⁺, CD11c⁺, CD14⁺, and CD16⁺ aggregates. (G) Expression of specific markers such as CD4, CD25, and CD127 (colors represent the median intensity of specified marker with red representing the brightest intensity and blue indicating no or minimal intensity). This figure provides a visualization of an expanded Treg (CD4⁺/CD25⁺/CD127^dim) population in a CMML patient with vs without BM IDC. (H) Quantitative analysis confirming an expanded Treg (% parentCD4 T cell) population in untreated CMML patients with BM IDC (n = 5) vs untreated CMML patients without BM IDC (n = 5; median, 14.5 vs 3.6; *P = .03). (I) GSEA showing significant enrichment of Treg-associated genes (normalized enrichment score [NES] = 3.97; ***P < .0001) through RNA-sequencing analysis of untreated PBMC samples derived from CMML patients (n = 4, indicated in red) with vs without (n = 4, indicated in blue) BM IDC (samples collected at the same time point as IHC assessment).