Expression of Mast Cell Proteases in Rat Lung during Helminth Infection: Mast Cells Express both Rat Mast Cell Protease II and Tryptase in Helminth Infected Lung

Abstract

Background: The phenotype of proliferated mast cells in Nippostrongylus brasiliensis–infected rat lung has been identified as mucosal mast cells (MMC) but not connective tissue mast cells (CTMC). However, a previous study of ours showed that the expression of rat mast cell tryptase (RMCT) mRNA, which has been reported to be confined to CTMC, significantly increased in rat lung 14 days after infection. Methods: The expression of four mast cell proteases in rat lung during the course of infection with N. brasiliensis was examined by RNA blot analysis. Immunohistochemical analysis of RMCT and rat mast cell protease (RMCP) II, which has been reported to be confined to MMC was also performed. Results: The number of lung mast cells did not change until 7 days after infection, then gradually increased until 21 days after infection. The expression of the RMCP II gene had increased 14 and 21 days after infection. In addition, the expression of the RMCP I and RMCT genes had also increased at the same time points, but RMCP III had not. By immunohistochemistry, most of the mast cells in infected lung were identified as RMCP II+/RMCT– (MMC), but both RMCP II+ and RMCT+ mast cells were also observed. Conclusions: The present results suggest that mast cell phenotype alteration or a distinct mast cell subset might be present in N. brasiliensis–infected rat lung, and therefore N. brasiliensis–infected rat lung may be a useful tool for studying the differentiation mechanism of mast cells.