CD19 and diffuse large B-cell lymphoma: Here we conducted a follow-up study of 58 DLBCL patients treated with CAR-T cell therapy, we analysed the killing of CD19/CD20-positive tumour cell line by infused CAR-T cells from all 56 evaluable patients in vitro, after excluding tumour-related factors, it was found that the anti-tumour function of CAR-T cells in resistant patients compared to the function of CAR-T cells in durable response (DR) patients.