Detection of Grb-2-related adaptor protein gene (GRAP) and peptide molecule in salivary glands of MRL/lpr mice and patients with Sjögren's syndrome.

The pathogenesis of Sjögren's syndrome (SS) is poorly understood. In this study we used an in-house mouse spleen cDNA microarray to analyse genes in spleens from MRL/lpr (an SS mouse model) mice. We have previously demonstrated that GRAP genes were up-regulated in salivary glands of the same mice. The microarray analysis showed that seven out of 2304 genes were highly expressed in spleens from the MRL/lpr mice, one of which was the GRAP gene. In other words, the GRAP gene is highly expressed in the salivary glands and spleen of MRL/lpr mice. We also carried out immunohistochemical studies. Mouse and human Grb-2-related adaptor protein (GRAP) antigens were expressed on ductal cells and infiltrating lymphocytes in salivary glands of MRL/lpr mice and SS patients, but only weakly in controls (MRL/+ mice and individuals with salivary cysts). These results suggest that the GRAP gene might have a role in the pathogenesis of SS.