Eotaxin-3 but not eotaxin gene expression is upregulated in asthmatics 24 hours after allergen challenge

Eotaxin is an important mediator of eosinophil recruitment and activation i n the airways of asthmatics. Eotaxin-2 and eotaxin-3 are two recently ident ified chemokines with activity similar to that of eotaxin. Using quantitati ve polymerase chain reaction analysis, we determined the messenger RNA (mRN A) expression of eotaxin, eotaxin-2, and eotaxin-3 relative to GAPDH mRNA e xpression in bronchial biopsies and bronchoalveolar lavage fluid (BALF) cel ls obtained from subjects with mild asthma, asthmatic subjects 24 h after a llergen challenge, and normal control subjects. In bronchial biopsies, gene expression was upregulated in asthmatic subjects as compared with control subjects for eotaxin (log median values 3.18 pg/mug, 95% confidence interva l [CI]; 2.27 to 3.79 versus 4.37 pg/mug, 95% CI; 3.97 to 4.65, P = 0.003) a nd for eotaxin-2 (0.82 pg/mug, 95% CI; 0.08 to 1.72 versus 2.97 pg/mug, 95% CI; 1.97 to 3.45, P = 0.006), but no further increase was observed after a llergen challenge. In contrast, eotaxin-3 mRNA expression was not increased in asthmatic compared with control subjects, but was dramatically enhanced 24 h after challenge (median log value 1.93 pg/mug, 95% CI; 0.74 to 3.92 v ersus 4.62 pg/mug, 95% CI; 3.05 to 6.23, P = 0.036). No significant differe nce between groups was observed in BALF cell gene expression for any of the chemokines examined. These data suggest that eotaxin-3 rather than eotaxin or eotaxin-2 may account for the ongoing eosinophil recruitment to asthmat ic airways in the later stages (24 h) following allergen challenge.