Mast Cell FcεRI Expression in the Rat Intestinal Mucosa and Tongue Is Enhanced during Nippostrongylus brasiliensis Infection and Can Be Up-Regulated by in Vivo Administration of IgE

The activation of rodent and human mast cells can occur through the cross-linking of tetrameric IgE receptors each containing single α- and β- and two γ-subunits. However, the factors that regulate the in vivo expression of FcεRI are poorly understood. We have examined the expression of the FcεRI β-subunit in the Nippostrongylus brasiliensis (Nb)-induced model of rat intestinal inflammation. We developed a double-staining technique for mast cell granules (Alcian blue) and the β-subunit of FcεRI. The intensity of immunohistochemical staining per mast cell was quantified using an image analysis system. Jejunal and tongue mast cells of Lewis rats were visible by Alcian blue staining before Nb infection, but they expressed very low levels of β-subunit as assessed by immunohistochemical staining. These levels were increased by day 11 postinfection and reached a maximum at day 14. Since serum IgE levels correlated well with the degree of β-subunit expression, we investigated whether the observed enhancement of receptor expression might occur through the stabilization of receptor complexes by IgE. Therefore, Lewis rats were treated with myeloma IgE, and β-subunit expression was examined. In both tongue and jejunal tissue, a significant rise in β-subunit expression was observed in response to IgE injection, although levels of β-subunit expression were not as high as those observed in Nb-infected animals. The increase in β-subunit expression was accompanied by an increase in the amount of mast cell-associated IgE. These observations may have important implications for the regulation of IgE receptor expression during disease.