We investigated the incidence of B-cell clonality in the minor salivary gland and liver (extra-glandular lesion) of patients with Sjögren's syndrome (SS). We also compared B-cell clonality in the minor salivary gland and liver in the same individuals, and compared its incidence among patients with various liver diseases, such as primary biliary cirrhosis (PBC) and autoimmune hepatitis (AIH).
A minor salivary gland biopsy was performed on 35 patients with SS (30 patients with primary SS, and five patients with secondary SS). A liver biopsy was performed on nine patients with SS associated with bile duct lesions, two patients with PBC, one patient with AIH, one patient with drug-induced liver dysfunction, and three patients with viral hepatitis. DNA was extracted from each tissue sample and then subjected to Polymerase Chain Reaction (PCR). B-cell clonality was analysed by assessing the rearrangement of the immunoglobulin heavy chain (IgH) gene by PCR.
B-cell clonality was confirmed in the minor salivary gland biopsy sample in 23 of the 35 patients (65.7%), and in the liver biopsy sample (non-exocrine organ involvement) in seven of the nine patients (77.8%). The presence or absence of B-cell clonality was investigated in both the minor salivary gland and liver in seven patients, but B-cell clonality was confirmed in both tissues in only one patient, and the pattern of clonality in the minor salivary gland differed from that in the liver. B-cell clonality was detected in the liver of the PBC and AIH patients.
B-cell clonality is a phenomenon that is observed frequently in SS lesions in the salivary glands and liver. The appearance of B-cell clonality was shown to be attributable to antigen-driven clonal expansion.