Higher CD8⁺T-cell numbers at baseline and early on-therapy associate with favorable PFS and no infections with ibrutinib-rituxumab. (A) Schematic representation of the E1912 trial and biobanked peripheral blood mononuclear cell samples collected at baseline (B/L) and 6- (6M) and 12- (12M) month time points for correlative T-cell analysis. PFS, infection, and MRD clinical outcome data were collected. (B) Absolute numbers of CD8⁺ T_EM cell subsets (CD45RA⁻CCR7⁻) for ibrutinib-rituximab (n = 86 patients) and FCR (n = 50) at the time points indicated. Patient data are presented as Box and whiskers (10-90 percentile; log scale) plots. (C) Percentage of PD-1⁺ CD8⁺ T_EM subsets during ibrutinib-rituximab (n = 86) or FCR (n = 50) treatments. (B-C) Data are given as the mean ± standard error of the mean; statistical analysis between time points were assessed using the Wilcoxon signed-rank test. (D) Tabular schematic summary of the significant correlations (Cox model) between higher immune subset levels (flow cytometry, median values used as cut-off point) and PFS for patients on ibrutinib-rituximab (n = 88 patients with 13 experiencing disease progression). Green rows (correlations with hazard ratio [HR] values < 1) indicate higher immune subsets associated with longer PFS, whereas higher immune subsets associating with shorter PFS (HR > 1) are highlighted in blue rows. Confidence intervals (95%) and P values are shown. (E) Schematic summary of the significant correlations (Wilcoxon test) between immune subsets and infection (any infection) during ibrutinib-rituximab treatment (n = 88 patients). Negative t statistics (t.stat) indicate higher immune subset levels in patients who did not develop infection (green rows). In contrast, correlations with a positive t.stat indicate higher immune subset levels in patients who developed infection (blue rows). (F) Kaplan-Meier curves of immune subsets associated to good prognosis for the ibrutinib-rituximab arm. Higher levels of percentage PD-L1⁺ CD19⁺ cells (high: 12 progression events per 43 patients and low: 1 progression event per 43 patients), absolute number of PD-1⁺CD8⁺ T_EM (high: 3 progression events per 43 patients and low: 10 progression events per 43 patients), and PD-1⁺CD4⁺ T cells (high: 3 progression events per 43 patients and low: 10 progression events per 43 patients) at baseline associate with longer PFS. Higher percentage of CD8⁺ T_EM (high: 3 progression events per 42 patients and low: 10 progression events per 43 patients) at the 6-month time point associate with longer PFS. Absolute number data are referred to as “ab.” P values indicated. ∗P < .05; ∗∗P < .01; ∗∗∗∗P < .0001. n/s, not significant.