Asthma is characterized by allergic airway inflammatory response involving extensive leukocyte infiltration. The stromal cell-derived factor (SDF)-1 or chemokine (C-X-C motif) ligand 12 (CXCL12) attracts a number of cells, including resting T lymphocytes, monocytes, CD34+ stem cells, basophils, and mature eosinophils. To date, however, the potential role of CXCL12/SDF-1 in relation to leukocyte recruitment in asthma has not been previously examined, to our knowledge.
Levels of CXCL12/SDF-1 in the BAL fluid (BALF) of 15 subjects with asthma and 13 healthy subjects were measured by enzyme-linked immunosorbent assay. Immunohistochemistry was performed to identify the cellular source of this chemokine.
CXCL12/SDF-1 concentrations were significantly elevated in BALF from subjects with asthma compared with normal subjects (median 845 pg/mL, range, 296-1,700 pg/mL vs median 55 pg/mL, range 25-97 pg/mL; P < .001). Concentrations of CXCL12/SDF-1 correlated with macrophages (r = 0.728, P < .01), lymphocytes (r = 0.651, P < .01), and eosinophils (r = 0.765, P < .01). By immunohistochemistry, CXCL12/SDF-1 was localized to the airway epithelium and to a lesser extent to mononuclear cells.
CXCL12/SDF-1 is released in high concentration in BALF of patients with asthma. The finding that concentrations of this chemokine correlated with leukocyte numbers in BALF suggests that this chemokine may contribute to the cell recruitment in asthma.