OBJECTIVETo investigate the expression of proteasome immunosubunit low molecular weight polypeptide (LMP)2 and LMP7 in labial glands of patients with primary Sjogren's syndrome patients, and thus explore their role in the diagnosis, differential diagnosis and pathogenesis of primary Sjogren's syndrome (pSS).

METHODSLabial specimens were collected from 40 patients with pSS, 15 patients with connective tissue diseases other than pSS, and 9 healthy controls. The expressions of LMP2 and LMP7 in labial specimens were determined using immunohistochemical approaches and analyzed using semi-quantitative methods. The positive rate of acinar was calculated. After the square arcsine transformation of data, the differences of the positive rate in acinar between LMP2 and LMP7 were compared among three groups. Spearman's rank correlation coefficient was used for analyzing the correlation of clinical manifestations with LMP2 and LMP7 expressions.

RESULTSThe expressions of LMP2 and LMP7 within the acinar and ductal epithelial cells were confirmed. Although the LMP2 expression in labial specimens was not significantly different among three groups(P=0.369), the expression of LMP7 was significantly higher in pSS patients compared with patients with connective tissue disease and healthy controls (P<0.01). Only in pSS group, LMP7 was found to be with higher positive rate in acinar than LMP2 (P<0.01). No significant correlation was found between LMP2/LMP7 and clinical manifestations (P>0.05).

CONCLUSIONIn patients with pSS, the expression of LMP7 (but not LMP2) is up-regulated in labial gland, indicating these two proteins have different genetic regulation mechanisms.