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Departments of
*
Medicine and
Pathology, Harvard Medical School, Boston, MA 02115; and
Division of Rheumatology, Immunology, and Allergy and
§
Department of Pathology, Brigham and Womens Hospital, Boston, MA 02115
Recombinant mouse mast cell protease 6 (mMCP-6) was generated to
study the role of this tryptase in inflammatory reactions. Seven to
forty-eight hours after the i.p. injection of recombinant mMCP-6 into
BALB/c, mast cell-deficient
WCB6F1-Sl/Sld, C5-deficient,
or mMCP-5-null mice, the number of neutrophils in the peritoneal cavity
of each animal increased significantly by >50-fold. The failure of the
closely related recombinant tryptase mMCP-7 to induce a comparable
peritonitis indicates that the substrate specificities of the two
tryptases are very different. Unlike most forms of acute inflammation,
the mMCP-6-mediated peritonitis was relatively long lasting and
neutrophil specific. Mouse MCP-6 did not induce neutrophil chemotaxis
directly in an in vitro assay, but did promote chemotaxis of the
leukocyte in the presence of endothelial cells. Mouse MCP-6 did not
induce cultured human endothelial cells to express TNF-
, RANTES,
IL-1
, or IL-6. However, the tryptase induced endothelial cells to
express large amounts of IL-8 continually over a 40-h period. Neither
enzymatically active mMCP-7 nor enzymatically inactive pro-mMCP-6 was
able to induce endothelial cells to increase their expression of IL-8.
Although the mechanism by which mMCP-6 induces neutrophil accumulation
in tissues remains to be determined, the finding that mMCP-6 induces
cultured human endothelial cells to selectively release large amounts
of IL-8 raises the possibility that this tryptase regulates the steady
state levels of neutrophil-specific chemokines in vivo during mast
cell-mediated inflammatory events.
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