T cells expressing CD7 CARs fail to expand. (A) Schematic diagram of control (ΔCAR) and full-length CD7 CAR constructs used in the study. (B) Surface expression of the CD7 CAR constructs on retrovirally transduced T cells measured by flow cytometry using anti-human IgG Fc antibodies on day 6 posttransduction. (C) Expansion of T cells transduced with truncated (ΔCAR) of full-length CD7 CAR in vitro for 14 days. (D) Viability of CD7 CAR T cells at days 2 and 6 posttransduction measured by flow cytometry. (E) Expression of CD7 in nontransduced or CD7 CAR-transduced activated T cells. A CD7-negative cell line Raji was used as a negative control. Data represent 2 to 5 independent experiments with n = 3 donors in each. Ctrl, control; Neg., negative; ns, not significant; NTR, nontransduced. *P < .05; **P < .001.