Fig. 1　Microbial ligand-dependent and independent regulation of immune homeostasis.

In bone marrow mesenchymalstem cells (MSCs), NOD1 senses the peptides glycan derived from commensal bacteria. Upon ligand recognition, MSCs produce hematopoietic cytokines that promote the proliferation of hematopoietic stem cells and progenitor cells (HSPCs) (upper panel). In addition, cytokine stimulation induces cytosolic interactions between NOD1 and STAT5 in HSCs and peripheral T cells, whose binding is essential for their proliferation and survival (lower). These pathways ensure optimal hematopoiesis.