Sec61 plays an essential role in facilitating antigen cross-presentation to induce immune glomerular injury: a novel ‘self-organized criticality theory’ explaining cause of SLE (BA8P.129)

Abstract

Abstract Objective: Our novel ‘self-organized criticality theory’ which may explain the cause of SLE shows that immune glomerular injury is caused by CTL generated via antigen cross-presentation. Here we show essential role of Sec61 in antigen cross-presentation and immune glomerular injury. Methods: Bone marrow-derived dendritic cell (BMDC) was cultured with fluorescent-labeled OVA. Early endosome antigen 1 (EEA1), calnexin and Sec61 were detected using immunofluorescent staining. Sec61 was immunoprecipitated from OVA-pulsed BMDC lysate, followed by immunoblotting of OVA. Mice were repeatedly immunized with OVA to induce SLE. Splenic DC (spDC) was cultured with fluorescent-labeled OVA to examine localization of engulfed antigen. Further, exotoxin A was co-immunized with OVA to inhibit Sec61. Results: In BMDC, OVA was co-localized with an endosomal marker EEA1, and subsequently separated from EEA1. OVA was co-localized with Sec61, but not the ER marker calnexin. The result was similar when spDC was used. Engulfed OVA was co-precipitated with Sec61, and the amount of Sec61 in endosome was increased after repeated immunization with OVA. Instead, inhibition of Sec61 did not induce CTL nor renal injury, suggesting that OVA interacts with Sec61 hence exported from endosome to cytoplasm via Sec61. Conclusion: Increase of Sec61 in endosome and the export of antigen from endosome to cytoplasm via Sec61 are important for antigen cross-presentation and as the cause of immune glomerular injury.