Bone marrow DCs engulf apoptotic myeloma cells via CD91. Myeloma tumor antigens are then processed and presented on class I HLA molecules to activate infiltrating CD8⁺ T cells. At the same time, using CD80/CD86, these DCs interact with nonapoptotic myeloma cells that express higher levels of CD28 compared with plasma cells from patients with monoclonal gammopathy of undetermined significance (MGUS). As a result, proteasome degradation occurs, which impairs tumor antigen expression on the myeloma cells thereby rendering them more resistant to T-cell recognition and killing. Professional illustration by Patrick Lane, ScEYEnce Studios.