The DARC-CD82 axis discloses bone marrow macrophages as guardians of long-term hematopoietic stem cells quiescence

In all adult tissues, there is a constant supply of differentiated cells provided by the existence of stem and progenitor cells capable of dividing according to the organism’s demands. One of the most paradigmatic tissues regarding the study of stemness and differentiation is the hematopoietic system. Blood homeostasis is sustained by a subset of cells known as hematopoietic stem and progenitor cells (HSPCs). This is a heterogeneous population that includes from the most immature cells, which have the ability to self-renew and give rise to cells of all blood lineages, to the so-called progenitors, whose differentiation capacity is restricted to a single lineage and display a more limited number of divisions. To date, the main way of distinguishing hematopoietic cells in different stages of maturation has been the use of surface markers based on their restricted or exclusive expression (1). Nevertheless, these markers per se do not show functional characteristics of the cells, since generally only their restricted expression is exploited, but not their biological activity.