ABSTRACT
Multiple myeloma (MM) is characterized by the uncontrolled proliferation and accumulation of monoclonal plasmablasts and plasma cells (PCs) in the bone marrow (BM).1,2 Normal PCs are the effector arm of the humoral immune response and are the mainstay of the immune defence against foreign invaders. Although morphologically homogeneous, PCs are a functionally heterogeneous compartment of terminally differentiated B-cell populations. They all develop from mature B cells upon antigen (Ag) stimulation but, when arising in different environmental scenarios, become endowed with different biological properties. Until recently, little has been known about the biology of normal PCs and, while advances have been made in some areas, such as the molecular events that are necessary for a B-lineage cell to become a PC, other aspects of normal PC biology, such as the life span of PCs, remain incompletely defined.
