To investigate whether interferon-inducible protein 10 (IP-10) is involved in the inflammatory process of the labial gland of patients with Sjogren's Syndrome (SS).
Forty-nine patients performed labial gland biopsy, the number of lymphocytes in the biopsy tissues was calculated and the IP-10 was detected by the methods as following: 39 biopsied labial tissues were examined by RT-PCR, among them, 21 were from primary SS, 5 from secondary SS and 13 from other diseases. With RT-PCR, the IP-10 and beta-actin were co-amplified with specific primers. The gel-fractioned and ethidium bromide amplification products were then analyzed by densitometry. The expression of IP-10 was semi-quantificated by IP-10/beta-actin ratio. Twenty-one samples were examined by immunohistochemistry with specific goat anti-IP-10 antibody, 10 of them from primary SS, 3 from secondary SS, 8 from other diseases. 11 out of 21 samples were examined by both RT-PCR and immunohistochemistry.
The expression of IP-10 mRNA was significantly up-regulated in labial glands of patients with SS compared with other diseases (IP-10/beta-actin ratio was 0.329 +/- 0.157 vs 0.099 +/- 0.059, P < 0.01). The number of lymphocyte infiltration foci in labial glands of patients with SS correlated to the IP-10/beta-actin ratio (r = 0.657, P < 0.05). Ductal epithelial cells and some of the infiltrating lymphocytes were stained by anti-IP-10 antibody by immunohistochemistry in 8 of the primary SS (8/10), all of the secondary SS (3/3) and one with primary biliary sclerosis (1/8). The expression of IP-10 protein detected by immunohistochemistry was consistent with that of mRNA detected by RT-PCR.
IP-10 is abnormally highly expressed in the labial glands of patients with SS and positively relates to the lymphocyte infiltration. It thus suggests chemokine IP-10 may be one of the important molecules attracting the lymphocytes to the minor salivary glands to form the lymphocytic foci of Sjogren's Syndrome.