HAVCR2 and plasma cell myeloma: Given that significant differences were observed between HD and late relapsed multiple myeloma populations in the above analysis, and late relapsed multiple myeloma is the most relevant group for CAR T-cell treatment, we assessed the expression of the immune checkpoint molecules PD-1, TIGIT, LAG3, and TIM3 on HD-derived and late relapsed multiple myeloma-derived CAR T cells by flow cytometry.