Increased interleukin (IL)-7Rα expression in salivary glands of patients with primary Sjogren's syndrome is restricted to T cells and correlates with IL-7 expression, lymphocyte numbers and activity.

OBJECTIVE: To identify interleukin (IL)-7Rα expression in the labial salivary gland (LSG) of patients with primary Sjögren's syndrome (pSS) and non-Sjögren's syndrome sicca (nSS-sicca) and to study its correlation with glandular inflammation and IL-7 expression.
METHODS: The presence of infiltrating immune cells and IL-7Rα cells in inflamed LSG of patients with pSS (n=12) and nSS-sicca controls (n=7) was studied by immunohistochemistry and fluorescence activated cell sorting analysis upon tissue digestion (n=15 and n=13, respectively). Additionally, the correlations of IL-7Rα cells with hallmark disease parameters of pSS, major infiltrating inflammatory cells and IL-7 were assessed.
RESULTS: In the LSG of patients with pSS increased numbers of IL-7Rα cells were found as compared with nSS-sicca patients. IL7Rα cells strongly correlated with the lymphocytic focus score, IL-7 expression, the decrease in percentage of IgA plasma cells and numbers of CD3 T cells, CD20 B cells, and CD1a and CD208 myeloid dendritic cells. Analysis of isolated cells from the LSG demonstrated strongly increased percentages of IL-7Rα CD3 T cells in pSS as compared with nSS, showing abundant IL-7Rα expression on both CD4 and CD8 T cells. Other CD45 leucocytes and CD45- tissue cells scarcely expressed IL-7Rα. Percentages of IL-7Rα T cells also significantly correlated with glandular inflammation.
CONCLUSIONS: This study shows the presence of increased IL-7Rα T cells in the LSG of patients with pSS and their association with the severity of sialadenitis, disease parameters and IL-7 expression. Considering the immunostimulatory ability of IL-7Rα T cells and IL-7, this suggests that IL-7(R)-dependent T cell-driven immune activation plays an important role in inflammation in pSS.