MAST-CELL FC-EPSILON-RI 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 cr oss-linking of tetrameric IgE receptors each containing single alpha- and beta- and two gamma-subunits. However, the factors that regulate t he in vivo expression of Fc epsilon RI are poorly understood. We have examined the expression of the Fc epsilon RI beta-subunit in the Nippo strongylus brasiliensis (Nb)-induced model of rat intestinal inflammat ion. We developed a double-staining technique for mast cell granules ( Alcian blue) and the beta-subunit of Fc epsilon RI. The intensity of i mmunohistochemical staining per mast cell was quantified using an imag e analysis system. Jejunal and tongue mast cells of Lewis rats were vi sible by Alcian blue staining before Nb infection, but they expressed very low levels of beta-subunit as assessed by immunohistochemical sta ining. 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 beta-subunit expression, we investigated whether the observe d enhancement of receptor expression might occur through the stabiliza tion of receptor complexes by IgE. Therefore, Lewis rats were treated with myeloma IgE, and beta-subunit expression was examined. In both to ngue and jejunal tissue, a significant rise in beta-subunit expression was observed in response to IgE injection, although levels of beta-su bunit expression were not as high as those observed in Nb-infected ani mals. The increase in beta-subunit expression was accompanied by an in crease in the amount of mast cell-associated IgE. These observations m ay have important implications for the regulation of IgE receptor expr ession during disease.