IL13RA1 and neoplasm: Using the tumor line A549, which endogenously expresses IL13Rα1, but not IL13Rα2, we found that the IL13-28ζ CAR T cells exhibited the most off-target–mediated degranulation (Fig. 6C), activation marker expression (Fig. 6D), in vitro cytotoxicity (Fig. 6E), and proliferation (Fig. 6F).