Tripterygium Wilfordii inhibits tonsillar IgA production by downregulating IgA class switching in IgA nephropathy

IgA nephropathy (IgAN) is characterized by high serum IgA levels and IgA deposition in the renal mesangium. Recent research has indicated that pathogenic IgA may originate from affected tonsils, where present enhancement of IgA production by IgA class switching and immuno-activation. Tripterygium Wilfordii (TW) was found to be especially effective in IgAN by its' immunosuppression effect. Given this background, we investigated the mechanisms underlying the role of TW in the generation of IgA and IgA class switching in tonsillar GCs of IgAN patients. Immunohistochemistry and RT-PCR revealed that the expression of thymic stromal lymphopoietin (TSLP) and IgA inducing cytokines were decreased in the tonsils of IgAN patients with TW treatment compared with those without treatment, followed by significantly decreased of IgA-bearing cells. The location of TSLP and IgA inducing cytokines in tonsillar tissue was confirmed by double immunofluorescence. Importantly, TW inhibit TSLP and IgA production in isolated FDC-associated clusters. Serum TSLP levels were decreased and correlated with IgA downregulation in the tonsils and serum of IgAN patients. These data indicated that TW may be involved in IgA production in the tonsils of IgAN patients, inhibiting IgA class switching in IgAN patients through the cooperative roles of AID, TGF-β1, BAFF, and APRIL, highlighting a promising strategy for therapeutic intervention in IgAN.