The immunosuppressive capacity of osteoclasts has also been described in the context of multiple myeloma, where the production of immunosuppressive molecules such as indoleamine 2,3-dioxygenase (IDO) and PD-L1 by osteoclasts protects myeloma cells against T-cell-mediated cytotoxicity [217]. This evidence concerns the gene IDO2 and plasma cell myeloma.