A suppressive role of STAT1 in lupus-like chronic graft versus host disease (IRM7P.479)

Abstract

Abstract Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease driven by genetic and environmental factors with unknown etiopathogenesis. The bm12→B6 chronic graft-versus-host disease (cGVHD) is a well-studied inducible mouse model of SLE. STAT1 is dynamically regulated during the course of immune and inflammatory responses. However, little is known about the role of STAT1 in autoimmune diseases. We induced cGVHD in B6.STAT1-KO and B6.WT mice by intraperitoneally injection of 1×108 splenocytes from bm12 mice. Mice were followed for autoimmune manifestations, such as mortality, skin rash, and renal involvement. Upon injection, WT mice developed anti-dsDNA autoantibodies starting at week 2 (as expected), with decline noted after week 4. In contrast, STAT1-deficient mice exhibited a prolonged and significant increase of anti-dsDNA autoantibody responses compared to WT mice (week 4 to week 8). Severe splenomegaly also developed in cGVHD STAT1-KO mice. Increased autoantibody titers were accompanied by increased proteinuria in mice lacking STAT1 due to immune complex deposition. Three months after injection, 40% of the STAT1-KO mice with cGVH disease were dead. Anti-dsDNA isotypes in cGVH diseased STAT1-KO mice were enhanced (IgG1 responses), but IgG3 responses were absent. STAT1 seems to suppress systemic autoimmunity by altering autoantibody isotype switching. Results from these studies may provide insights into the pathogenesis of STAT1 in SLE.