Involvement of autoimmunity to REG , a regeneration factor, in patients with primary S jögren's syndrome

Summary The regenerating gene ( R eg ) was isolated originally as a gene specifically over‐expressed in regenerating pancreatic islets and constitute a growth factor family. R eg gene product ( R eg) is important in the pathophysiology of various human inflammatory diseases. Recently, the possible involvement of human REG in the regeneration of salivary ductal epithelial cells of patients with primary S jögren's syndrome ( SS ) was reported. However, the expression of the REG family genes in minor salivary glands ( MSG ) and the occurrence of anti‐ REG I α autoantibodies in SS patients were obscured. In this study, we examined the expression of REG family genes in the MSG of SS and screened anti‐ REG I α autoantibodies in SS . The mRNA levels of REG family genes in MSG were quantified using real‐time reverse transcription–polymerase chain reaction ( RT – PCR) and REG I α expression in the MSG was analysed by immunohistochemistry. The mRNA level of REG I α in the MSG of SS patients was significantly higher than that of control. REG I α protein was expressed highly in SS ductal epithelial cells. Anti‐ REG I α autoantibodies in the sera were found in 11% of SS . All the MSG in the anti‐ REG I α autoantibody‐positive group showed REG I α expression, whereas only 40% showed REG I α expression in the anti‐ REG I α autoantibody‐negative group. The anti‐ REG I α autoantibody‐positive group showed significantly lower saliva secretion and a higher ratio of grade 4 (by R ubin– H olt) in sialography. These data suggest strongly that autoimmunity to REG I α might play a role in the degeneration of MSG ductal epithelial cells in primary SS .