Abstract
BackgroundsThe organization of minor salivary glands (MSG) infiltrates, in patients with Sjögren’s syndrome (SS), associates with disease severity and progression. Aberrant regulation of lymphocyte autophagy is involved in autoimmunity, and in previous work, we provided the first evidence of upregulated autophagy in CD4+ T cells infiltrating SS MSG. The aim of this study was to further explore autophagy in SS infiltrating and circulating lymphocytes and to investigate its role in disease histopathological progression.MethodsAfter collection of 20 SS MSG, the presence of lymphocyte aggregates (foci) and the formation of germinal center (GC)-like structures were observed by H&E and confirmed by immunohistochemistry. The expression of autophagy-related genes, Atg5 and MAP1LC3A, was detected by RT-PCR on microdissected salivary gland tissue and control tonsils. In MSG and tonsils, autophagic lymphocytes were identified by the detection of the autophagosome protein LC3B visualized as LC3 puncta staining by immunofluorescence. Peripheral blood autophagy was assessed by flow cytometry in SS and healthy controls (HC).ResultsReal-time PCR demonstrated higher expression in the autophagy genes Atg5 and MAP1LC3A in MSG GCs as compared to both small foci (p = 0.0075, p = 0.0002) and GCs from tonsils (p = 0.0001, p = 0.0037). In MSG, LC3 puncta staining was detectable on both CD3+ and CD20+ lymphocytes; in tonsils, LC3 puncta was almost undetectable on all lymphocytes. Compared to HC (n = 20), flow cytometry did not reveal any increase of autophagy in SS circulating lymphocytes (n = 30).ConclusionsIn SS MSG, lymphocytes’ autophagy is a feature of infiltrating T and B cells and is associated with histological severity. Interestingly, in MSG aberrant regulation of autophagy is detectable in GC-like structures possibly indicating its involvement in the development and persistence of the autoimmune process within the lesions.
Highlights
Autophagy is a cell-protective catabolic process aimed at eliminating damaged organelles, misfolded proteins, and intracellular pathogens [1]
In minor salivary glands (MSG) aberrant regulation of autophagy is detectable in Germinal centers (GCs)-like structures possibly indicating its involvement in the development and persistence of the autoimmune process within the lesions
Autophagy is upregulated in s syndrome (SS) GC-like structures compared to the classic GCs inhabiting secondary lymphoid organs
Summary
Autophagy is a cell-protective catabolic process aimed at eliminating damaged organelles, misfolded proteins, and intracellular pathogens [1]. Thanks to the ability to shape the adaptive immune response, deregulation of autophagy mechanisms seems implicated in the development of autoimmunity [2]. Autophagy seems able to shape the adaptive immune response, orchestrating the regulation of lymphocyte survival, differentiation, and activation [3]. LC3-II plays a crucial role in cargo selection and autophagosome biogenesis and is thereby widely utilized as a marker of autophagy activation [5]. LC3, which is identified by three different forms named LC3A, LC3B, and LC3C [6], is a structural protein of the autophagosomal membranes used as a biomarker of autophagy. The cytoplasmic presence of LC3B, which is measured by immunofluorescence as an increase in punctate LC3 named “LC3 puncta” stain, is widely used to monitor autophagy [7, 8]
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