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Histochemical and ultrastructural modification of mucosal mast cell granules in parasitized mice lacking the
J M Wastling1, P Knight, J Ure
1Department of Veterinary Clinical Studies, University of Edinburgh, United Kingdom.
Abstract:
The soluble beta-chymases mouse mast cell protease-1 (mMCP-1) and rat mast cell protease-II are predominantly expressed by intestinal mucosal mast cells (IMMCs) and may promote mucosal epithelial permeability when released during intestinal allergic hypersensitivity responses. To study the function of these chymases, we generated mice with a homozygous null mutation of the mMCP-1 gene and investigated their response to infection with the intestinal nematode Nippostrongylus brasiliensis. Whereas mMCP-2, -4, and -5 were transcribed normally, there was no transcription of the mMCP-1 gene in null (-/-) mice, nor was mature mMCP-1 protein detected in (-/-) jejunal mucosa. In contrast, levels of mMCP-1 in wild-type (+/+) jejunal mucosa increased 200- to 350-fold from 0.66 microg mMCP-1/g wet weight in uninfected mice to 129 and 229 microg/g wet weight on days 8 and 10 of infection, respectively. The kinetics of IMMC recruitment differed in -/- mice compared with +/+ controls on days 8 (P < 0.05) and 10 (P < 0.03) of infection. The IMMCs in infected -/- mice stained poorly, if at all, for esterase with naphthol AS-D chloroacetate compared with the intense staining observed in +/+ controls. Ultrastructurally, the prominent crystal intragranular structures that are found in intraepithelial +/+ IMMCs were absent from -/- IMMCs. These data show that disruption of the mMCP-1 gene leads to profound histochemical and ultrastructural changes in IMMC granules.
Insights
Mice lacking mouse mast cell protease-1 (mMCP-1) showed altered intestinal mast cell characteristics during parasitic infection. This suggests mMCP-1 is crucial for normal mast cell granule development and function in the gut.
Area of Science:
- Immunology
- Gastroenterology
- Parasitology
Background:
- Soluble beta-chymases, such as mouse mast cell protease-1 (mMCP-1), are primarily found in intestinal mucosal mast cells (IMMCs).
- These proteases may influence intestinal epithelial permeability during allergic reactions.
Purpose of the Study:
- To investigate the function of mMCP-1, researchers generated mice lacking the mMCP-1 gene.
- The study examined the response of these knockout mice to Nippostrongylus brasiliensis infection.
Main Methods:
- Generation of homozygous null mutation mice for the mMCP-1 gene.
- Assessment of mMCP-1 gene transcription and protein levels in jejunal mucosa.
- Analysis of IMMC recruitment, histochemistry (esterase staining), and ultrastructure during parasitic infection.
Main Results:
- Mice lacking mMCP-1 showed no gene transcription or protein expression.
- Wild-type mice exhibited a significant increase in mMCP-1 levels during infection.
- mMCP-1 deficient mice displayed altered IMMC recruitment kinetics, poor esterase staining, and absent intragranular structures in IMMCs.
Conclusions:
- Disruption of the mMCP-1 gene results in significant histochemical and ultrastructural alterations of IMMC granules.
- These findings highlight the critical role of mMCP-1 in the development and characteristics of intestinal mast cells.