Mucosal defense against gastrointestinal nematodes:: Responses of mucosal mast cells and mouse mast cell protease 1 during primary Strongyloides venezuelensis infection in FcRγ-knockout mice

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