Professional antigen presenting cells in minor salivary glands in Sjögren's syndrome: potential contribution to the histopathological diagnosis?

Sjögren's syndrome is an autoimmune disease in which lymphocytic infiltrates develop in the salivary and lacrimal glands. We have shown that dendritic cells (DC) infiltrate the submandibular gland of the nonobese diabetic (NOD) mouse, a mouse model for Sjögren's syndrome, before lymphocytic infiltration, suggesting that these antigen-presenting cells (APC) may play a role in the initiation of Sjögren's syndrome. In later stages, DC and macrophages also form an important part of the infiltrate of the NOD sialoadenitis. To find out if DC and macrophages form part of the infiltrate in Sjögren's syndrome as well, and to determine whether they may be useful in the histopathological diagnosis of Sjögren's syndrome, we studied their presence in minor salivary glands (MSG) of patients with Sjögren's syndrome and patients with focal lymphocytic sialoadenitis (FLS), but without clinical or serological criteria of Sjögren's syndrome. Immunohistochemistry was applied, followed by semiquantitative analysis. DC and macrophages were present in all MSG; however, there were clear differences in marker expression between Sjögren's syndrome and FLS, on the one hand, and control tissue, on the other hand. CD1a+ DC and RFD9+ macrophages were mainly observed in MSG in which a focal lymphocytic infiltrate was present. In fact, the diffuse presence of single CD1a+ DC and RFD9+ macrophages correlated closely with the presence of a focal lymphocytic infiltrate in the MSG. This indicates that these cells could be of help during the evaluation of a MSG. Because the detection of APC is technically less cumbersome than a focal score, this parameter may perhaps replace the focal score in the histopathological diagnosis of Sjögren's syndrome. This study therefore prompts further investigation focusing on the presence of CD1a+ and RFD9+ cells in the MSG of a large cohort of patients.