ICPs and risk of progression to clinical myeloma. (A) Expression of PD-L1 on tumor cells and risk of progression to CMM requiring therapy. (B) Expression of PD-L1 on CD3⁺ T cells and risk of progression to clinical myeloma requiring therapy. (C) Expression of PD-L1 on CD4⁺ T cells and risk of progression to clinical myeloma requiring therapy. (D) Effect of PD-L1 blockade on antigen-dependent proliferation of SOX2-specific T cells in culture.