Cytotoxic T Lymphocyte Antigen-2 alpha (CTLA-2 alpha) is expressed in various epithelial cells in mammalian, and is known for its specific and high affinity inhibition of cathepsin L. In the submandibular gland, cathepsin L is expressed by interstitial cells and gingival fibroblasts. However, the expression of CTLA-2 alpha in salivary glands has never been demonstrated. The objective of this study was therefore to examine the expression of CTLA-2 alpha in rat major salivary glands and to assess its cellular localization with cathepsin L, so as to deduce their functional implications in salivary secretion. Results showed that CTLA-2 alpha is strongly expressed by ductal epithelial cells in granular convoluted tubules of the submandibular salivary gland, striated and excretory ducts, blood vessels and nerve bundles of all salivary glands. Immunoreactivity was weak in intercalated ductal cells but was absent in secretory acinar cells in all the glands. Double immunofluorescence labeling was performed to determine whether CTLA-2 alpha and cathepsin L in the salivary glands were localized within the same cell. Colocalization was detected in epithelial cells of the duct system, blood vessels and nerve bundles of the glands. These results are suggestive of the specific physiological functions of CTLA-2 alpha and cathepsin L in ductal cells of the salivary glands, and implicate the two in the salivary fluid modification, processing and releasing of neuropeptides and polypeptides in the salivary fluid.
