Fig. 1.

Proposed mechanism of GM-CSF receptor signal modulation by the laminin receptor (LR). Circulating granulocytes and monocytes are not activated by low levels of GM-CSF due to the binding of the LR to the GM-CSF receptor α (αR) and β (βR) subunits. On transendothelial migration, these cells attach to the basement membrane via interactions of the LR and the integrin receptor (IR) with extracellular matrix (ECM) proteins such as laminin, fibronectin, and collagen. This process relieves the inhibitory effects of the LR on GM-CSF signaling and increases the proliferation, survival, and maturation of myeloid cells and augments their host defense function.