Figure 2: Overlapping niches for HSCs and lymphopoiesis in the bone marrow.

MPCs are the main source of IL-7 in bone marrow. Hematopoietic stem cells (HSC, cyan), multipotent progenitors (MPP, blue) and common lymphoid progenitors (CLP, violet) are distributed in proximity of CXCL12^Hi IL-7⁺ SCF⁺ MPC. ProB (magenta) and motile preB cells (purple, amoeboid shaped cell with ruffled edges) predominantly localize near or in contact with IL-7⁺ MPCs, with proB cells spending longer periods of time in contact with IL-7⁺ cells than preB cells. MPCs can differentiate into osteolineage cells and to adipocytes. T-biased CLPs (blue-green) depend on Notch-ligand DLL4 possibly provided by MPCs, and natural killer (NK, green) cells on IL-15. Osteoclast precursor migration towards endosteal areas is mediated by the receptor EBI2 and oxysterol ligands. Larger arteries are surrounded by a-SMA⁺ pericytes, while NG2⁺ pericytes localize next to arterioles. Dashed arrows indicate movement, full arrows indicate differentiation. Circles represent chemokines and growth factors according to the color code shown in the upper right corner.