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 in the airways of asthmatics. Eotaxin-2 and eotaxin-3 are two recently identified chemokines with activity similar to that of eotaxin. Using quantitative polymerase chain reaction analysis, we determined the messenger RNA (mRNA) expression of eotaxin, eotaxin-2, and eotaxin-3 relative to GAPDH mRNA expression in bronchial biopsies and bronchoalveolar lavage fluid (BALF) cells obtained from subjects with mild asthma, asthmatic subjects 24 h after allergen 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/μg, 95% confidence interval [Cl]; 2.27 to 3.79 versus 4.37 pg/μg, 95% Cl; 3.97 to 4.65, P = 0.003) and for eotaxin-2 (0.82 pg/μg, 95% Cl; 0.08 to 1.72 versus 2.97 pg/μg, 95% Cl; 1.97 to 3.45, P = 0.006), but no further increase was observed after allergen 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/μg, 95% Cl; 0.74 to 3.92 versus 4.62 pg/μg, 95% Cl; 3.05 to 6.23, P = 0.036). No significant difference 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 asthmatic airways in the later stages (24 h) following allergen challenge.