Interleukin-17 as a biomarker for lupus nephritis: correlation with disease activity indices and histopathological classification

Abstract
Background
Lupus nephritis (LN) is one of the devastating manifestations of systemic lupus erythematosus (SLE). It is a leading cause of death in SLE patients. Interleukin 17(IL-17) is involved in the development of several autoimmune diseases. It causes inflammation and organ damage by exaggerating the immune response and augmenting antibody production by B cells. We assessed the role of IL-17A in LN and its relation to other markers of disease activity and different histopathological classes.

Results
We evaluated serum IL-17A in forty LN patients and thirty SLE patients without LN (non-LN). We found that LN patients had a significantly higher IL-17A level in comparison to non-LN. In the LN group, IL-17A was positively correlated with the systemic lupus erythematosus disease activity index (SLEDAI), protein/creatinine (P/C) ratio, 24-hour urinary proteins, anti-nucleosome, and anti-dsDNA antibodies and negatively correlated with C3 and C4. IL-17A was higher in class III and IV compared to class II and V LN. ROC curve analysis of IL-17A revealed 75% sensitivity and 76.7% specificity for LN, and the AUC was 0.791.

Conclusion
Lupus nephritis patients have a higher serum level of IL-17A than those without LN, which is more pronounced in patients with class-III and IV LN. Moreover, IL-17A has good sensitivity and specificity for LN and correlates with the disease activity indices; hence, it may be a prognostic marker for LN in SLE patients.