Essential roles of IL-12 and dendritic cells but not IL-23 and macrophages in lupus-like diseases initiated by cell surface HSP gp96

Proinflammatory cytokine IL-23 but not IL-12 is critical for the pathogenesis of organ-specific autoimmune diseases including experimental autoimmune encephalitis and collagen-induced arthritis. The contribution by IL-23 in systemic autoimmune diseases such as lupus is undefined. We addressed this question in a murine lupus-like disease model, initiated by enforced cell-surface expression of an ER HSP gp96 in C57BL/6 background. We found a significant increase of p40 in the sera in these mice that preceded the onset of diseases. However, autoimmunity was abrogated in transgenic mice expressing membrane-bound gp96 reconstituted with p35(-/-) BM, but not with p19(-/-) BM. Moreover, we found that dendritic cells (DC) but not macrophages were the main producers of p40. To dissect the roles of DC further, we depleted DC using a diphtheria toxin-based inducible DC depletion system. We demonstrated that the integrity of DC was essential for autoimmunity. Our results thus revealed that IL-12 and DC are critical for the pathogenesis of lupus-like disease precipitated by cell surface gp96. This study further highlighted the significant biological differences between IL-12 and IL-23.