Ectopic lymphoid follicles are considered morphological indices of local chronic antigen stimulation. The objective of this study was to present a detailed histopathological and immunohistochemical analysis of ectopic lymphoid follicles in salivary glands in Sjögren's syndrome (SS), compared to lymphoid follicles in lymph nodes.
Samples of labial salivary glands from 37 patients with primary and 57 with secondary SS were examined by histopathology and immunohistochemical methods with monoclonal antibodies (DAKO) to identify follicular dendritic cells, T and B lymphocytes, immunoglobulins and class II MHC HIA DPQR. Lymph nodes from 2 patients with primary SS were also examined for the same markers.
Focal inflammatory infiltrations in labial salivary glands in 64.9% of primary and 23.1-49.6% secondary SS were found to morphologically mimic lymphoid follicles in various stages of development. Secondary ectopic lymphoid follicles resemble the histological structure and immunohistochemistry of germinal centers in lymphoid follicles in reactive lymph nodes due to the large number of centrally located B cells (CD20+), reticular pattern of dendritic cells (CD21+) and T helper/inducer cells (CD4+). The centers of secondary ectopic lymphoid follicles contain deposits of IgG and IgM.
Ectopic lymphoid follicles quite often present in labial salivary gland in SS show structural and immunohistochemical features typical for lymphoid tissue. These ectopic follicles are the place of immune complex trapping, antigen presentation on dendritic cells and initiation of autoimmunologic response. This finding seems be very important for better understanding of the pathogenesis and diagnosis of SS as an autoimmunlogical disorder.