Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by producing large quantities of antibodies directed against self-antigens, particularly double stranded DNA (dsDNA) and small nuclear RNA-binding proteins such as Ro, La, Sm, and nRNP.
SLE-associated autoantibodies and high serum interferon alpha (IFN-α) are two important heritable phenotypes in SLE which are thought to play a role in disease pathogenesis . The most remarkable feature of the anti DNA response is its association with immunopathologic events especially glomerulonephritis . Immune complexes containing DNA can promote the expression of interferon alpha (IFN-alpha) by a specialized population of dendritic cells known as plasmacytoid dendritic cells .
Activation of the type I interferon (IFN) system is associated with disease pathogenesis in SLE, with affected patients typically demonstrating high concentrations of type I IFN proteins . Overexpression of type I IFN-induced genes that includes hundreds of gene transcripts; which is termed interferon signature (IFNGS), has been observed in 60-80% of adults and the majority of children with SLE .
Galectin-9 (Gal-9) is recognized as a novel, easy to measure biomarker for type1 IFN signatures and galectin-9 could aid in clinical decision making in SLE as a marker for disease activity and organ damage.
Galectin-9 is expressed by T cells, macro-phages, fibroblasts, and endothelial cells, its secreted form is barely detected under physiological conditions, it plays an recognizable role in the regulation of inflammation and immune responses by down-regulating pro-inflammatory T cells.
