T-cell subsets associated with the malignant transformation of SMM. (A) UMAP of the entire T-cell compartment and CD4 and CD8 subsets in PB of 150 patients with SMM. (B) Risk stratification according to the presence of −4 or fewer vs −4 or more points (prognostic scores of 1 and 2, respectively) based on 1, 2, or 3 points being attributed according to low, intermediate, or high frequency of double-positive (DP), TCD4⁺CD28⁺CD127⁺, TCD4⁺CD28⁺TIGIT⁺CD127^low, Treg TIGIT⁺CD39^dim, Treg TIGIT⁺CD39⁺, and TCD8⁺CD28^–TIGIT⁺PD1⁺CD127⁺ T cells. (C) Pie charts display the distribution of patients based on the 2/20/20 [>2 g/dL of serum M-protein, >20% serum free light-chain ratio, and >20% plasma cells found by BM biopsy] risk model of the IMWG in each subgroup of patients defined by their immune score. Significant differences were observed in the frequency of patients with low risk according to the IMWG when comparing patients with low- and high-risk immune scores.