PDCD1 and plasma cell myeloma: In addition, it is known that CD8+ T cells from myeloma patients co-express other immune checkpoints, such as LAG-3, TIM-3, CTLA4, and TIGIT (31–33) suggesting multiple pathways limiting T-cell responses at this stage of disease and thus explaining the lack of effect from PD-L1/PD-1 blockade as monotherapy.