Immune reconstitution after <scp>CD7 CAR</scp> ‐T cell therapy for refractory/relapsed acute T‐lymphoblastic leukaemia/lymphoblastic lymphoma (R/R T‐ <scp>ALL</scp> / <scp>LBL</scp> )

CD7 Chimeric Antigen Receptor-T cell (CAR-T) therapy demonstrates efficacy in relapsed/refractory (R/R) acute T-lymphoblastic leukaemia (ALL)T-ALL/lymphoblastic lymphoma (LBL), but concerns about T-cell depletion and severe immunodeficiency persist. We compared infection rates and immune cell subsets in 60 R/R T-ALL/LBL patients receiving naturally selected CD7 CAR-T (NS7CAR-T) with 60 R/R B-ALL patients undergoing CD19 CAR-T. Infections were monitored from infusion until allogeneic haematopoietic stem cell transplantation (HSCT) or up to 3 months. Overall infection rates did not significantly differ between groups (36.67% vs. 24.56%, p = 0.24), although the incidence of early immune effector cell-associated haematotoxicity (ICAHT) grade III-IV was higher in the CD7 CAR-T group than in the CD19 CAR-T group (33.9% vs. 16.7%, p = 0.03). Post-CD7 CAR-T infusion analysis showed a significant decline in CD7(+) T cells and an increase in non-CAR-T-derived CD7(-) T cells, particularly non-CAR-T cells, which rose to a median proportion of 84.4% (range: 22.1%-99.9%) by day 28; meanwhile, CD7(-) natural killer (NK) cells approached nearly 100% following the depletion of CD7(+) NK cells. This study indicates that while CD7 CAR-T therapy significantly reduces CD7(+) T cells, it does not lead to increased short-term infection rates. The notable expansion of non-CAR-T-derived CD7(-) T and NK cells helps preserve immune function, highlighting distinct therapeutic mechanisms between CD7 CAR-T and CD19 CAR-T due to their different lineage restrictions.