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. Author manuscript; available in PMC: 2013 Dec 1.
Published in final edited form as: Transfusion. 2012 Apr 9;52(12):2706–2716. doi: 10.1111/j.1537-2995.2012.03636.x

Figure 2.

Figure 2

Schematic representation of some of the interactions in response to G-CSF-induced mobilization. HSPC are retained in the bone marrow niche by adhesive interactions, such as between vascular adhesion molecule (VCAM)-1 and very late antigen (VLA)-4, and chemotactic interactions, such as between SDF-1 (green triangles) and CXCR4 receptor. Mobilizing signals (e.g., G-CSF) expand the number of granulocytes and activate the complement cascade. C5 cleavage fragments activate myeloid cells via the C5a receptor (C5aR) to release proteases (red and purple circles) which disrupt VCAM-1/VLA-4 and SDF-1/CXCR4 interactions. Membrane type-1 matrix metalloproteinase (MT1-MMP, black diamond) accumulates on the surface of granulocytes and HSPC and further facilitates their egress. In addition, C5 cleavage fragments chemoattract granulocytes and pave the way for the mobilization of HSPC across the endothelium. MAC generated in the final step of CC activation enhances the release of sphingosine-1 phosphate (S1P) from erythrocytes. S1P is also a potent chemoattractant for HSPC which express the S1P receptor.