Mucosal Defense against Gastrointestinal Nematodes: Responses of Mucosal Mast Cells and Mouse Mast Cell Protease 1 during PrimaryStrongyloides venezuelensisInfection in FcRγ-Knockout Mice

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Abstract
A possible role for the γ subunit of immunoglobulin Fc receptors (FcR) in mucosal defenses against intestinal nematode parasites was studied using age-matched FcRγ-knockout (FcRγ−/−) and wild-type (FcRγ+/+) C57BL/6 mice. Mice were infected subcutaneously with 3,000 infective larvae ofStrongyloides venezuelensis, and the degree of infection was monitored by daily fecal egg counts and adult worm recovery on days 8 and 13 postinfection. Mucosal mast cell (MMC) responses were assayed by in situ intestinal mast cell counts in stained histological sections of the jejunum and by measuring mouse mast cell protease 1 (MMCP-1) release in serum using sandwich enzyme-linked immunosorbent assay. FcRγ−/−mice had significantly higher egg counts (P< 0.01) and numbers of adult worms (P< 0.05) than FcRγ+/+mice, but mastocytosis and serum MMCP-1 release were comparable. It was concluded that MMCP-1 release may be spontaneous, does not depend on mast cell degranulation via the FcRγ signaling system, and appears to play no role in the expulsion ofS. venezuelensis. The delay in worm expulsion in the FcRγ−/−mice might be related to inability of the MMC to degranulate and release effector molecules other than MMCP-1, since FcRγ deletion abrogates mast cell degranulative responses.

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