In MM, osteoclasts can directly inhibit proliferative CD4+ and CD8+ T cells by upregulating immune checkpoint molecules such as programmed death ligand 1 (PD-L1), CD38, and Galectin-9, thus establishing the immunosuppressive microenvironment to protect myeloma cells (An et al., 2016). The gene discussed is CD274; the disease is plasma cell myeloma.