Mast cells associate with T-cells and neointimal microvessels in giant cell arteritis.

OBJECTIVE Mast cells (MCs) are known to be involved in the neovascularization and regulation of T cell responses. However, the presence of MCs in giant cell arteritis (GCA) is unknown. This prompted us to study the presence and phenotype of MCs in GCA. METHODS Human GCA specimens collected for diagnostic purposes were examined with immunohistochemistry. Double immunostainings of MC tryptase with cathepsin G, vascular endothelial cell growth factor (VEGF), CD3, and CD31/D34 were performed. RESULTS Double immunostainings showed that activated tryptase-, cathepsin G- and VEGF-expressing MCs associate with CD3+ T cells and CD31/CD34+ neointimal neovessels in the GCA lesions. CONCLUSIONS The results suggest that MCs may contribute to the pathogenesis of GCA putatively by regulating the functions of other inflammatory cells and resident vessel wall cells. Importantly, MCs promote neovascularization, which is considered as a prerequisite for the neointimal thickening in GCA.