LFA-1 expression by blood eosinophils is increased in atopic asthmatic children and is involved in eosinophil locomotion.

Allergic asthma is characterized by eosinophil migration in the airways, which is strictly dependent on the expression of adhesion molecules. This study investigated whether the expression of adhesion molecules on eosinophils is increased and associated with disease activity in allergic asthma. Twenty atopic asthmatic (AA) subjects and nine controls were studied and the expression of lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18), Mac-1 (CD11b/CD18) and very late antigen-4 (VLA-4; CD49d/CD29) on blood eosinophils was evaluated by specific monoclonal antibody (Mab) staining and flow-cytometric analysis. Compared with controls, eosinophils from AA showed increased expression of LFA-1 (p<0.005), but not of Mac-1 or VLA-4 (p>0.1). In addition, LFA-1 expression correlated positively with blood eosinophil number (r=0.792, p<0.05), while no correlations were observed between Mac-1 or VLA-4 expression and blood eosinophil number. The migration of eosinophils through human umbilical vein endothelial cells with or without anti-LFA-1, Mac-1 and VLA-4-blocking Mab was studied. Compared with controls, eosinophils from AA showed increased migration toward C5a (p<0.01). Cell migration was totally inhibited by preincubating eosinophils with anti-LFA-1 (p<0.05), while anti-Mac-1 had no effect (p>0.1). Thus, the expression of lymphocyte function-associated antigen-1 by blood eosinophils is increased in atopic asthmatics and seems to modulate the enhanced eosinophil migration observed in allergic asthma.