Background: Expression of receptors for IgE (Fc epsilon R) have been mainly studied on mast cells and blood basophils in the context of allergic disease, Some reports have noted limited expression of Fc epsilon R on other leukocytes, including blood monocytes and eosinophils in certain patients. An association between human blood basophil expression of Fc epsilon RI alpha and serum IgE has been noted among allergic subjects. Objective: Recent evidence supports regulation of Fc epsilon RI alpha by free IgE on both mast cells and basophils. We hypothesized that this relationship would exist across an extremely wide range of IgE levels for human basophils, irrespective of underlying disease. We further examined whether a similar relationship existed between serum IgE and Fc epsilon RI alpha or Fc epsilon RII (CD23) expression on monocytes and eosinophils in these same subjects. Methods: Blood was obtained from nonallergic subjects (n = 3) and subjects with allergic asthma (n = 5), atopic dermatitis (n = 3), hypereosinophilic syndromes (n = 7), hyper-IgE syndrome (n = 6), helminth infestation (n = 6), or IgE myeloma (n = 1). Levels of serum IgE were determined by using RIA and ranged from 3 to 4.7 mg/mL. Levels of cell surface Fc epsilon RI alpha, Fc epsilon RII, and IgE were measured by using immunofluorescence and now cytometry. Results: Basophil surface IgE density and Fc epsilon RI alpha expression correlated with serum IgE levels (r = 0.67 and r = 0.46, respectively; P < .01; n = 31) regardless of the disease state. In contrast, monocyte Fc epsilon RI alpha expression did not correlate with serum IgE (r = 0.09, P > .5, n = 29), and low-level eosinophil Fc epsilon RI alpha expression was only detected in a single asthmatic subject. CD23 expression was not detected on basophils or eosinophils, except for the eosinophils from the donor with IgE myeloma, CD23 was present on monocytes from some donors but did not correlate with serum IgE levels. Conclusions: In a variety of disease states, Fc epsilon RI alpha expression by basophils, but not monocytes or eosinophils, correlated with serum IgE levels across a 6-log range of IgE. These data support the concept of in vivo regulation of Fc epsilon RI alpha on basophils by serum IgE and further demonstrate that this is independent of allergic disease per se.
