Rapid transepithelial antigen transport in rat jejunum: impact of sensitization and the hypersensitivity reaction.
OBJECTIVE
Intestine from sensitized rats develops a rapid secretory response to luminal antigen challenge that depends on activation of subepithelial mast cells. The aim of this study was to determine the timing and route of the transepithelial protein antigen transport.


METHODS
Rats were sensitized to horseradish peroxidase (HRP). After 10-14 days, jejunal segments were resected, mounted in Ussing chambers, and challenged with HRP on the luminal side.


RESULTS
Electron microscopy of tissue specimens fixed at 2 minutes (before mast cell activation) showed enhanced endocytic uptake of HRP in enterocytes of HRP-sensitized rats compared with ovalbumin-sensitized or saline-injected controls. At this time, HRP was distributed throughout epithelial cells and was already evident in the lamina propria. In contrast, HRP was restricted to the apical region of enterocytes in controls. At 30 minutes (after mast cell activation), in HRP-sensitized rats only, HRP was also located within tight junctions and the paracellular region between epithelial cells. Tissue conductance was increased in HRP-sensitized rats beginning 30 minutes after HRP addition and correlated with the overall flux of HRP across the tissue.


CONCLUSIONS
The results show that specific sensitization enhances the initial uptake and transcytosis of antigen across intestinal epithelium. Subsequent to activation of mast cells, antigen transport is further enhanced by penetration through the paracellular pathway.
Berin
M C
MC
Intestinal Diseases Research Program, McMaster University, Hamilton, Ontario, Canada.
Kiliaan
A J
AJ
Yang
P C
PC
Groot
J A
JA
Taminiau
J A
JA
Perdue
M H
MH
D000818:Animals; D000941:Antigens / Q000378:metabolism*; D001692:Biological Transport; D004594:Electrophysiology; D006735:Horseradish Peroxidase / Q000493:pharmacokinetics; D006967:Hypersensitivity / Q000378:metabolism* / Q000503:physiopathology; D007114:Immunization; D007583:Jejunum / Q000378:metabolism* / Q000503:physiopathology / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D000941:Antigens; D006735:Horseradish Peroxidase