CD19 and neoplasm: To assess whether chronic CAR-mediated activation could lead to T cell dysfunction, we employed a co-culture system whereby every 72 h CXCR5 CAR-T or CD19 CAR-T cells were recursively transferred to culture dishes seeded with JeKo-1 cells, adjusting for a constant viable 1:1 CAR-T cell: tumor cell ratio31,34,35.