Evaluation of Serum Galectin-9 Level in Systemic Lupus Erythematosus Patients and it's Association With Disease Activity and Organ Damage

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.