CD44 EXPRESSION ON BLOOD EOSINOPHILS IS A NOVEL MARKER OF BRONCHIAL-ASTHMA

Bronchial asthma is characterized by infiltration of the respiratory t racts by eosinophils. A wide variety of adhesion molecules expressed b y eosinophils have been proposed to be involved in binding of eosinoph ils to the vascular endothelium and subsequent transmigration from the circulation to the airways, while little is known about CD44 expressi on on eosinophils. We introduced a novel staining combination with whi ch surface markers on eosinophils could be analyzed without purificati on prior to staining, and examined the expression of CD44 on eosinophi ls. Staining of eosinophils with anti-CD16 and anti-VLA-4 mAbs enabled us to delineate eosinophils as VLA-4(high) CD16-cells from any other leukocyte populations in the whole blood. CD44 was found to be constit utively expressed on resting eosinophils, and expression increased upo n cytokine-mediated activation. In all bronchial asthma patients exami ned, CD44(high) eosinophils were enriched in sputum relative to periph eral blood, indicating that eosinophils in sputum were more activated than those in blood. By comparing the extent of CD44 expression on blo od eosinophils from poorly controlled and well-controlled asthma patie nts, we unexpectedly found that the density of CD44 expression is high er on blood eosinophils from the well-controlled group. Thus, the exte nt of CD44 expression on blood eosinophils is a novel marker indicativ e of the mangement of bronchial asthma. Deterioration of the asthma ma nagement with a concomitant decrease in CD44 expression on peripheral eosinophils implies that CD44 may play an important role in facilitati ng the transmigration of activated, CD44(high) eosinophils from the ci rculation to the respiratory tracts.