Objective To investigate the expression of histone deacetylase 8 (HDAC8) in the labial gland of patients with Sj?gren's syndrome (SS), and whether it is related to the abnormal activation of B cells of SS patients. Methods The expression of HDAC8 was detected by immunohistochemistry in the labial glands from SS patients (n=10) and non-SS patients (n=4). The subtype of lymphocytes which expressed HDAC8 was determined by double staining immunofluorescence. Person correlation analyses were performed to evaluate the relation between the proportion of HDAC8 positive cells and the level of immunoglobulins in SS patients. Results The expression of HDAC8 in the labial gland from SS patients was significantly higher than that in the non-SS patients.The proportion of HDAC8 positive cells in lymphocytic foci was higher than that in scattered interstitial lymphocytes [(0.76±0.05) vs (0.40±0.03), t=18.5, P<0.01]. IF showed that HDAC8 was expressed in CD20+B cells, and CD138+plasma cells in labial gland from SS group,but not CD4+T cells. The ratio of HDAC8+cell in infiltrating lymphocytic loci was not related to the level of IgG or IgA of SS patients. Conclusion HDAC8 is expressed in CD20+B cells and CD138+plasma cells in labial gland from SS patients. These data suggests that HDAC8 may be involved in abnormally activated B cells and plasma cells in SS patients.