Abstract
BACKGROUND: Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is an adhesion molecule that directs naive T and B cells into Peyer's patches for sensitization and distribution to intestinal and extraintestinal sites. With no enteral stimulation, its expression drops rapidly in association with reduced Peyer's patch cell populations and increases rapidly with reinstitution of enteral feeding. Because both glutamine (GLN) and bombesin (BBS) preserve mucosal immunity, this study examined whether they preserve MAdCAM-1 expression. METHODS: In 2 separate experiments, animals were randomized to IV cannulation with chow, total parenteral nutrition (TPN), and (experiment 1) 15 microg/kg BBS 3 times per day or (experiment 2) an isocaloric, isonitrogenous 2% GLN-supplemented solution. After 5 days of feeding, MAdCAM-1 expression in Peyer's patches, spleen, and intestine was measured using a dual radiolabeled monoclonal antibody technique. RESULTS: MAdCAM-1 expression was not significantly improved from TPN levels either with BBS or GLN supplementation. Levels of MAdCAM-1 expression remained unchanged in non-Peyer's patch sites. CONCLUSIONS: Although MAdCAM-1 is considered the gateway molecule for cell entry into mucosal immunity, this does not seem to be the mechanism for mucosal immunity preservation in nonenterally fed mice receiving bombesin or glutamine.
MAdCAM-1 controls entry of naïve B and T cells into mucosal-associated lymphoid tissue. Its expression drops rapidly with IV feeding and recovers with enteral feeding. Both glutamine and bombesin preserve mucosal immunity through non-MAdCAM-1–related mechanisms.
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