Immune-mediated TTP is a life-threatening autoimmune disorder characterized by abundant occlusion of the microcirculation. iTTP is caused by a severe autoantibody-mediated deficiency of the von Willebrand factor cleaving protease, ADAMTS-13. Emerging evidence points to autophagy as key player driving dysregulated autoimmune responses in various diseases. Considering the crucial role of antigen-presenting cells (APCs) in the presentation of autoantigens, we assessed expression profile of autophagy (ATG)-related genes in iTTP.

We isolated splenic dendritic cells (DC) from one patient carrying the HLA DRB1*11 risk allele and leucocytes from peripheral blood of two healthy donors. Then pan-DCs including plasmacytoid and myeloid DCs were isolated by negative selection followed by FACS sorting. In parallel in vitro differentiated monocyte-derived dendritic cells (Mo-DCs) were cultured from freshly isolated MOs. The expression profile of six essential ATG genes (Beclin-1, Atg5, Atg7, Atg16L1, WIPI1 and LC3B) implicated in autoimmune diseases and the autophagic flux (LC3B expression) were determined by qPCR and detection of LC3B dot formation by immunofluorescence, respectively.

Upregulation of 5 ATG genes (Beclin-1, Atg5, Atg7, WIPI1 and LC3B) was observed in patient`s Mo- DCs compared to controls. Basal autophagy of individual pan-DCs versus Mo-DCs revealed a higher autophagic flux than pan-DCs with the highest autophagic flux displayed in Mo-DCs in the iTTP patient.

The observed activation of autophagy hints at a contribution to the loss of tolerance in iTTP. A more extensive study to investigate if modulators of the respective aberrantly expressed ATG genes might help improve therapy management is ongoing.