Relationships between eosinophil-associated parameters and disease severity in atopic dermatitis.

This study demonstrated not only the presence of house dust mite antigen (HDM)-specific IgE and IgG antibodies in the sera of 27 patients with atopic dermatitis (AD), but also considerably increased levels of serum eosinophil cationic protein (ECP) and uniformly nadir levels of plasma ECP, which provides evidence for ECP release from eosinophils in vitro. Besides blood eosinophilia, AD patients had an increased number of CD32+ eosinophils and EG2+ "activated" eosinophils; both of which, especially the latter, were significantly correlated with elevated levels of serum ECP. AD-source eosinophils had enhanced sensitivity for IgG-immune complexes corresponding to their increased expression of CD32, whereas neither HDM alone nor IgE/HDM-immune complex induced eosinophil activation. There were no gamma globulin-bearing cells in AD-source eosinophils, indicating that serum ECP levels may be dependent on EG2+ eosinophil numbers rather than the state of CD32-mediated eosinophil degranulation, as shown in vitro. Since HDM can cause an eczematous skin reaction accompanying the eosinophil accumulation and degranulation in sensitized AD, increased numbers of both CD32+ and EG2+ eosinophils according to the extent of AD severity indicates that these eosinophil in vivo generations and their subsequent functioning in the lesional skin may be regulated through HDM-initiated dermatitis events, and then, may form a vicious circle as the AD lesions spread.