Ectopic Lymphoid-like Structures Function As Microniches For Autoreactive B Cells In Pemphigus Lesions

Pemphigus is an autoimmune bullous disease with skin and mucous membranes as its target organs.A previous study shows lesional B cells could produce desmoglein specific antibodies and ectopic lymphoid-like structures exist in lesions of pemphigus vulgaris.However,the universal existence and pathological features of ectopic lymphoidlike structures;the phenotype and in situ differentiation of lesional B cells remains unclear.In our study,we found ectopic lymphoid-like structures commonly existed in lesions of both pemphigus vulgaris and pemphigus foliaceus.They mainly existed in form of mixed T and B cells with the presence of plasma cells and high endothelial venules-like vessels.Furthermore,pemphigus lesions contained a higher fraction of centroblasts,plasmablasts and plasma cells than PBMC.And elevated expression levels of BLIMP-1,IRF4 and BCL-6 were observed in pemphigus lesions than normal skin.In addition,BCR repertoire of pemphigus lesion showed obvious clonal expansion and shared some clonotypes with PBMC BCR repertoire.At last,increased levels of chemokines in pemphigus lesions and elevated expressions of chemokine receptors of lesional B cells may involve in the migration or residence of lesional B cells.Collectively,ectopic lymphoid-like structures in pemphigus lesions support in situ B cell differentiation and clonal expansion.