In allergic asthma experimental exposure to allergens is associated with depletion of blood eosinophils overexpressing LFA-1.
BACKGROUND
In atopic individuals, exposure to allergens is followed by recruitment of blood eosinophils in the target tissue. We investigated whether allergen inhalation challenge could result in depletion of blood eosinophils overexpressing adhesion molecules involved in eosinophil migration.


METHODS
Blood eosinophils were isolated from seven atopic asthmatic patients and seven control subjects and the "at baseline" expression of lymphocyte function-associated antigen-1 (LFA-1), macrophage antigen-1 (Mac-1) and very late antigen-4 (VLA-4) was assessed by monoclonal antibody staining and flow cytometry analysis. Asthmatic patients underwent allergen challenge and the expression of LFA-1, Mac-1 and VLA-4 by blood eosinophils was again evaluated 3 h and 24 h after allergen challenge.


RESULTS
As compared to controls, eosinophils from atopics showed at baseline enhanced LFA-1 expression (P=0.0012), but similar Mac-1 or VLA-4 expression (P > 0.1, each comparison). In atopics, the percentage and absolute number of blood eosinophils were significantly decreased 3 h after allergen challenge (P=0.001 and P=0.022, respectively) but returned to similar values to prechallenge values after an additional 21 h (P > 0.1). Allergen challenge was also followed by a significant decrease in LFA-1 expression by eosinophils, at 3 h (P=0.002) and at 24 h (P=0.038), while no changes in Mac-1 and VLA-4 were observed. A significant correlation between postchallenge decrease in LFA-1 expression and in blood eosinophilia, both expressed as percentage (r=0.88; P < 0.01) or absolute number (r=0.87; P < 0.01) was demonstrated at 3 h (r=0.88; P < 0.01) but not at 24 h (r=0.64, P > 0.05 and r=0.11; P > 0.05, respectively).


CONCLUSIONS
In allergic asthma, an early recruitment of blood eosinophils overexpressing LFA-1 occurs in the first hours after allergen challenge.
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000009:adverse effects*; D001249:Asthma / Q000097:blood* / Q000209:etiology*; D015815:Cell Adhesion Molecules / Q000097:blood / Q000187:drug effects; D004804:Eosinophils / Q000187:drug effects* / Q000378:metabolism*; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects*; D039041:Integrin alpha4beta1 / Q000096:biosynthesis / Q000187:drug effects; D007958:Leukocyte Count; D016169:Lymphocyte Function-Associated Antigen-1 / Q000096:biosynthesis* / Q000187:drug effects*; D016177:Macrophage-1 Antigen / Q000096:biosynthesis / Q000187:drug effects; D008297:Male; D039981:Pyroglyphidae; D012129:Respiratory Function Tests; D013223:Statistics as Topic; D013997:Time Factors; D014797:Vital Capacity / Q000502:physiology
D000485:Allergens; D015815:Cell Adhesion Molecules; D039041:Integrin alpha4beta1; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen