Prognostic significance of immune reconstitution following CD19 CAR T‐cell therapy for relapsed/refractory B‐cell lymphoma

Abstract Immune deficits after CD19 chimeric antigen receptor (CAR) T‐cell therapy can be long‐lasting, predisposing patients to infections and non‐relapse mortality. In B‐cell non‐Hodgkin lymphoma (B‐NHL), the prognostic impact of immune reconstitution (IR) remains ill‐defined, and detailed cross‐product comparisons have not been performed to date. In this retrospective observational study, we longitudinally characterized lymphocyte subsets and immunoglobulin levels in 105 B‐NHL patients to assess patterns of immune recovery arising after CD19 CAR‐T. Three key IR criteria were defined as CD4+ T helper (TH) cells > 200/µL, any detectable B cells, and serum immunoglobulin G (IgG) levels >4 g/L. After a median follow‐up of 24.6 months, 38% of patients displayed TH cells, 11% showed any B cells, and 41% had IgG recovery. Notable product‐specific differences emerged, including deeper TH cell aplasia with CD28z‐ versus longer B‐cell aplasia with 41BBz‐based products. Patients with any IR recovery experienced extended progression‐free survival (PFS) (median 20.8 vs. 1.7 months, p