Lymphocyte subset recovery following CAR19. Violin plots showing the distribution of absolute cell counts for CD19⁺ B cells (A), CD4⁺ T cells (B), CD8⁺ T cells (C), and CD4/CD8 ratio measured by flow cytometry (D) performed on peripheral blood samples over the total duration of follow-up post–axi-cel infusion. The dashed red lines in B and D denote clinically actionable thresholds below which antimicrobial prophylaxis is used at the study center. The number of patients at risk, as well as the number of patients who underwent testing (N), is shown by time point below each plot. P values were obtained using the Kruskal-Wallis test; each time point was treated as an independent group.