[6] Stromal cell-derived factors 1-alpha and 1-beta are small cytokines that belong to the chemokine family, members of which activate leukocytes and are often induced by proinflammatory stimuli such as lipopolysaccharide, TNF, or IL1.

The CXCL12 proteins belong to the group of CXC chemokines, whose initial pair of cysteines are separated by one intervening amino acid.

[13] CXCL12 is expressed in many tissues in mice including brain, thymus, heart, lung, liver, kidney, spleen, platelets and bone marrow.

[16][17][18][19] During embryogenesis, it directs the migration of hematopoietic cells from fetal liver to bone marrow and the formation of large blood vessels.

CXCL12 is also chemotactic for mesenchymal stem cells and is expressed in the area of inflammatory bone destruction, where it mediates their suppressive effect on osteoclastogenesis.

[20] In adulthood, CXCL12 plays an important role in angiogenesis by recruiting endothelial progenitor cells (EPCs) from the bone marrow through a CXCR4 dependent mechanism.

Elevated levels of CXCL12 are observed in the cerebral spinal fluid of patients with MS. CXCL12 crosses the blood–brain barrier and causes neuroinflammation that contributes to axonal damage and therefore the progression of multiple sclerosis.

[32][unreliable medical source] Though CXCL12 may be detrimental for those with MS, recent research is suggesting that this chemokine may be beneficial in decreasing the progression of patients with Alzheimer's.

[33][unreliable medical source] Additionally, this pretreatment with CXCL decreased the prevalence of apoptosis and oxidative damage normally caused by the presence of the beta-amyloid plaque.

[35] For instance, blocking CXCR4, the receptor for CXCL12, with Plerixafor (AMD-3100) increased the effectiveness of combretastatin in a mouse model of breast cancer, presumably by preventing macrophages from being recruited to tumours.

[15][16] AMD-3100 is also widely used in combination with G-CSF for mobilizing hematopoietic stem cells into the blood stream, allowing collection for bone marrow transplant.