Differentiation and CD23 expression of peripheral blood monocytes in patients with atopic dermatitis

In this study we investigate the expression of the low affinity immunoglobulin E (IgE) receptor (Fc epsilon RII) on plastic-adherent leucocytes from patients with atopic dermatitis (AD). Peripheral blood mononuclear cells were obtained from patients with AD, normal controls (and in one study from a group of atopic asthmatic patients). Monocytes were separated by 2-h adherence to plastic. These cells were then cultured for up to 7 days. Cells were harvested at time 0 (after adherence), and after 5 and 7 days culture, and cytospins were prepared. The proportion of cells expressing the phenotype of antigen presenting cells (monoclonal antibodies (mAb) RFD1+), and mature phagocytes (mAb RFD7+) together with CD23, were evaluated using combination staining with immunoperoxidase and alkaline phosphatase anti-alkaline phosphatase methods. It was found that a significantly larger proportion of circulating adherent cells in AD patients expressed the RFD1 antigen, and that increases in the proportion of these adherent cells expressing RFD1 or RFD7 occurred faster as cells matured in culture, when compared with cells obtained from normal controls. By day 7, however, equivalent proportions of RFD1+ and RFD7+ cells were present in AD and control cultures. None the less, expression of the CD23 molecule was consistently present on a larger proportion of both RFD1+ and RFD7+ cells from AD patients compared with controls. The raised proportion of circulating RFD1+ cells found in AD was not present in samples from atopic asthmatics, while the raised expression of CD23 on these cells occurred in samples from both these groups. These data support the suggestion that abnormalities in peripheral blood adherent cell phenotype, maturation, and CD23 expression, occur in AD patients. Some of these observations may be related to atopy in general rather than being specific for this skin disease.