CD28 and precursor B-cell acute lymphoblastic leukemia: Results from clinical trials for relapsed/refractory B-ALL also showed that CD19-CAR-T cells using CD28 as a co-stimulatory molecule triggered a high level of pro-inflammatory cytokine production early after infusion to the patients (NCT01593696, NCT02186860, NCT01044069) (5, 38, 39), which is also consistent with preclinical data on CD28-based CAR-T (40, 41).