ABSTRACT
The strategic localization of mast cells near blood vessels led us to investigate the involvement of these cells in IgG-antigen complex-mediated inflammation, using mast-cell-deficient mice and their congenic controls. Mast cells were extensively degranulated and contributed to neutrophil influx, plasma exudation, fibrin deposition, edema formation, and tissue damage. Leukotrienes and the tumor necrosis factor (TNF) from mast cells participated in neutrophil elicitation, and histamine and leukotrienes in plasma exudation, fibrin deposition, and edema formation. Reconstituting the deficient mice with mast cells restored the responses, confirming the role of mast cells and their mediators. Studies with decomplemented and C5-deficient mice indicate that mast cells were stimulated by complement early in the reaction and later by an unknown mechanism. The findings show that mast cells and their mediators, such as leukotrienes, histamine, and TNF, play an important role in the initiation of IgG-antigen complex-mediated inflammation.
ABSTRACT
Chronic inflammatory diseases of the gastrointestinal tract such as ulcerative colitis and Crohn's disease are characterized by mast cell proliferation and secretion of inflammatory mediators. The determinant(s) responsible for stimulating mast cells in the intestinal mucosa is not known. We investigated the interaction of mast cells with type 1 fimbriated Escherichia coli, an opportunistic pathogen and a constituent of the normal indigenous microflora of the gut. Unlike a mutant derivative deficient in the FimH subunit of the fimbriae or nonfimbriated E. coli, type 1 fimbriated E. coli adhered avidly to mast cells. As a consequence of this interaction, the mast cells phagocytozed and killed adherent bacteria. The mast cell bactericidal activity involved generation of superoxide anion and acidification of phagocytic vacuoles. In addition, many of the mast cells had degranulated and released inflammatory mediators such as histamine. These observations have implications both for normal host defense and for the initiation and perpetuation of inappropriate inflammatory responses in the gastrointestinal tract.
