Mast cells in the colon of Trypanosoma cruzi-infected patients: are they involved in the recruitment, survival and/or activation of eosinophils?

Megacolon is frequently observed in patients who develop the digestive form of Chagas disease. It is characterized by dilation of the rectum-sigmoid portion and thickening of the colon wall. Microscopically, the affected organ presents denervation, which has been considered as consequence of an inflammatory process that begins at the acute phase and persists in the chronic phase of infection. Inflammatory infiltrates are composed of lymphocytes, macrophages, natural killer cells, mast cells, and eosinophils. In this study, we hypothesized that mast cells producing tryptase could influence the migration and the activation of eosinophils at the site, thereby contributing to the immunopathology of the chronic phase. We seek evidence of interactions between mast cells and eosinophils through (1) evaluation of eosinophils, regarding the expression of PAR2, a tryptase receptor; (2) correlation analysis between densities of mast cells and eosinophils; and (3) ultrastructural studies. The electron microscopy studies revealed signs of activation of mast cells and eosinophils, as well as physical interaction between these cells. Immunohistochemistry and correlation analyses point to the participation of tryptase immunoreactive mast cells in the migration and/or survival of eosinophils at the affected organ.