CD4 cytotoxic and dendritic cells in the immunopathologic lesion of Sjogren's syndrome

The existence of CD4(+) T lymphocytes with cytotoxic activity in minor sali vary gland (MSG) biopsies from Sjogren's syndrome (SS) patients was investi gated using in situ double immunohistochemistry technique. The presence of dendritic cells (DC) in SS lesions was examined by using single and double immunohistochemistry methods and a panel of different MoAbs to specific cel l surface markers (i.e. CD3, CD11c, DRC). Furthermore, the ultrastructural morphology of DC was characterized by electron microscopy (EM). Immunogold labelling technique using the DRC surface marker was also applied. Finally, we investigated the existence of germinal centres (GC) in the salivary gla nd lesions of SS patients. Seven patients with primary SS and five patients with non-specific sialadenitis were the subjects of this study. Our result s indicate the existence of a CD4(+) cytotoxic cell population that utilize s perforin-mediated cell destructions as they expressed perforin mRNA. Quan titative analysis of these cells revealed that they comprised approximately 20% of the existing T lymphocytes. We also identified a population of CD4( +) T cells that expressed the CD11c activation marker. Furthermore, we obse rved a distinct cell subtype which expressed the DRC cell surface marker. T hese cells had the characteristic ultrastructural morphology of DC and were DRC+ when examined by immunoelectron microscopy. Finally, the formation of GC structures in the histopathologic lesions of the salivary glands was ob served. The above findings indicate that both CD4(+) cytotoxic T lymphocyte s (CTL) and DC may be involved in the initiation and perpetuation of SS pat hogenesis. Moreover, the formation of GC in the lesions reveals a possible mechanism for insiru differentiation and proliferation of activated B lymph ocytes.