Characterization of lymphoid infiltrates in chronic obstructive sialadenitis associated with sialolithiasis

Chronic obstructive sialadenitis is characterized by acinar atrophy, lymphocytic infiltrates and progressive fibrosis. The immunological mechanisms involved in the pathogenesis of this disease are, for the most part, unknown. The aim of the present study was to characterize the lymphocytic infiltrates in chronic obstructive sialadenitis associated with sialolithiasis.

Paraffin-embedded tissue samples from 23 affected submandibular glands were immunostained for T-cells (CD3, CD4, CD8), cytotoxic T-cells (granzyme B), B-cells (CD20), plasma cells (CD38) and macrophages (Ki-M1P).

CD4-positive subsets were the predominant cells, and they were located mainly periductally. Isolated intraepithelial CD8-positive cytotoxic T-cells associated with ductal epithelial cell destruction were observed in all cases. B lymphocytes were restricted to lymphoid follicles located periductally and around intralobular ducts. In early stages of the disease, a large number of CD38-positive plasma cells were distributed diffusely in the periacinar area. With progression of the disease, conspicuous clusters of plasma cells were located especially between atrophic acini adjacent to fibrotic tissue. An intimate relation between the lymphocytic infiltrates and the ductal epithelium, the target of the inflammatory process, was observed.

The composition and distribution of inflammatory cells suggest that intraepithelial infectious agents may be the cause of the inflammatory reaction and the progressive fibrosis in this disease.