CD19 and neoplasm: B cell aplasia is a classical on-target/off-tumor toxicity in patients treated with anti-CD19 or 20 CAR-T cells (Maude et al., 2014a; Zhang et al., 2016a; Kochenderfer et al., 2012), which can easily be managed with intravenously (i.v.)Ig replacement and serve as a surrogate maker for the persistence of CAR-T cells in vivo (Maude et al., 2014a).