CD19-CAR T cells expressing low levels of CD7 mark functional CD4⁺ effector CAR T cells in patients with refractory/relapsed B-ALL. (A) Violin plot of single-cell CD7 expression across 21 transcriptional clusters of clinical-grade CD19-CAR T-cell products and postinfusion samples from 16 patients with refractory/relapsed B-ALL. Data represent 184 791 transcriptionally identified CD19-CAR T cells. Transcriptional clusters were annotated using several key markers outlined in supplemental Table 1. (B) Dot plot of relative CD7 expression across transcriptional clusters from panel A. Dot size corresponds to the percentage of cells expressing any amount of CD7 as indicated. (C) Violin plot of single-cell CD7 expression from select clusters from panel A across sampling timepoints and clinical-grade CD19-CAR T-cell products as indicated by color. (D) Dot plot of relative expression of CD7 across functional annotations group as shown in (A). Dot size corresponds to the percentage of cells expressing any amount of CD7 as indicated. (E) Violin plot comparing expression of CD7 within the CAR⁺ CD4⁺ cytotoxic effector cells (cluster 14) between patients with complete response to therapy at 4 weeks after infusion (Responders) and patients without complete response to therapy (Nonresponders). Wilcoxon rank-sum with Bonferroni correction, adjusted P = 2.309236e-106. (F) Boxplot representing the proportion of CAR⁺ CD4⁺ cytotoxic effector cells (cluster 14) with no detected CD7 transcripts across patients with and without response to therapy. Boxplots indicate the median (middle bar), the 25th, and the 75th percentiles (lower and upper hinges, respectively) and 1.5 times the interquartile range from each hinge (whiskers). Wilcoxon rank-sum exact test, P = 0.03.