Activation of MKK4 (SEK1), JNK, and c-Jun in labial salivary infiltrating T cells in patients with Sjögren's syndrome.

We wanted to determine via immunohistochemistry, whether or not c-Jun NH2-terminal kinase (JNK) cascade is activated in labial salivary infiltrating T cells in patients with Sjögren's syndrome (SS). Six patients with primary SS were selected for this study. Phosphorylation of mitogen-activated protein kinase (MAPK) kinase 4 (MKK4) (SEK1), JNK, and c-Jun in salivary infiltrating T cells was studied using immunohistochemistry assay, including mirror section technique. Phosphorylated forms of MKK4, JNK, and c-Jun were detected in salivary infiltrating mononuclear cells. Expression of phosphorylated JNK was found in both CD4+ T cells and CD8+ T cells. Moreover, co-expression of phosphorylated JNK and c-Jun was demonstrated in the mirror sections. The results of this study suggest that the JNK cascade is activated in salivary infiltrating CD4+ T cells and CD8+ T cells in SS patients, which appears to contribute to the inflammatory salivary microenvironment of SS.