THE INFLUENCE OF MAST-CELLS ON PATHWAYS OF TRANSEPITHELIAL ANTIGEN TRANSPORT IN RAT INTESTINE

Luminal Ag challenge of intestinal segments from sensitized rats resul ts in a rapid (similar to 3 min) secretory response. We previously sho wed in horseradish peroxidase (HRP)-sensitized rats that the initial p hase of transepithelial Ag transport occurred via a transcellular rout e and was enhanced by sensitization, However, following the hypersensi tivity reaction, Ag also crossed between epithelial cells, The aim of this study was to determine the role of mast cells in the altered tran sepithelial Ag transport. White spotting mast cell-deficient rats and +/+ littermate controls were sensitized to HRP, After 10 to 14 days, j ejunal segments were resected, mounted in Ussing chambers, and challen ged with HRP on the luminal side. Electron microscopy of jejunum fixed at 2 min showed a similarly enhanced endocytic transport of HRP in se nsitized +/+ and Ws/Ws rats compared with naive controls. In sensitize d +/+ rats, a secretory response occurred similar to 3 min after chall enge, and tissue conductance increased thereafter. Naive +/+ and sensi tized Ws/Ws rats did not demonstrate a secretory response to HRP chall enge, and conductance remained at baseline levels. The flux of HRP was elevated across tissue from sensitized +/+ rats but not across tissue from naive controls or sensitized Ws/Ws rats. The results indicate th at sensitization enhances the initial phase of transepithelial uptake of Ag by transcytosis in a mast cell-independent manner. However, subs equent recruitment of the paracellular pathway for Ag transport in sen sitized rats is dependent upon the presence of mast cells and occurs a fter the activation of such cells.