Targeting the molecular and cellular interactions of the bone marrow niche in immunologic disease.

Recent investigations have expanded our knowledge of the regulatory bone marrow (BM) niche, which is critical in maintaining and directing hematopoietic stem cell (HSC) self-renewal and differentiation. Osteoblasts, mesenchymal stem cells (MSCs), and CXCL12-abundant reticular (CAR) cells are niche components in close association with HSCs and have been more clearly defined in immune cell function and homeostasis. Importantly, cellular inhabitants of the BM niche signal through G protein-coupled surface receptors (GPCRs) for various appropriate immune functions. In this article, recent literature on BM niche inhabitants (HSCs, osteoblasts, MSCs, CAR cells) and their GPCR mechanistic interactions are reviewed for better understanding of the BM cells involved in immune development, immunologic disease, and current immune reconstitution therapies.