Comparison of human tonsillar mast cell localization and ultrastructural observations between IgE-mediated allergic...

Mast cells (MCs) are important effector cells in mucosal defense and allergic inflammation. Lymphoid tissues such as tonsils and adenoids also have modest numbers of MCs. However, the role of MCs in lymphoid tissues is not well known. In this study, we showed the local distribution of MCs in tonsils from IgE-mediated allergic or nonallergic donors, studied their ultrastructure, and specified their surrounding cell types. Tonsils were obtained from IgE-mediated allergic or nonallergic donors suffering from chronic tonsillitis or hyperplastic tonsils. The localization and distribution of MCs and IgE binding to MCs were determined by immunohistochemistry using antibodies against tryptase, c-kit, and IgE. In addition, mast cell structure was examined using electron microscopy. In both allergic and nonallergic donors, MCs were distributed mainly in the interfollicular area and the perivascular area of connective tissue. We found that the total number of MCs in tonsils was almost the same in both donor groups. However, the number of MCs in the interfollicular area was significantly higher in nonallergic versus allergic donors. Moreover, the electron microscopy revealed that MCs localized in perivascular areas of connective tissue have scroll-type granules, and MCs in the interfollicular areas contained both particle and scroll-type granules. In addition, the MCs that were surrounded by CD4+ lymphocytes in the interfollicular area showed empty granules, whereas MCs in the perivascular area, not surround by CD4+, were intact. This implies that these MCs were degranulated, and this probably was caused by CD4+ cells. Taken together, these findings suggest that tonsillar MCs distribute differently in allergic and nonallergic donors, and that MCs in the interfollicular area might be activated by direct contact with CD4+ T cells.