CXCL12 and obesity due to melanocortin 4 receptor deficiency: HCD-depletion of the Common Lymphoid Progenitor (CLP) and B cell-differentiation-promoting CXCL12 abundant reticular (CAR) cells in the BM (25) additionally reinforces the myeloid/lymphoid bias (66) as does the HCD enhancement of Nestin+ MSCs, which drive the adipocyte bias of the BM niche in obesity (25).