The relationship between serum A proliferation-inducing ligand and B-cell activating factor levels with disease activity and organ involvement in systemic lupus erythematosus.

Objectives: We aim to investigate the association between serum B-cell activating factor (BAFF) and A proliferation-inducing ligand (APRIL) levels with disease activity and clinical findings in SLE patients. Methods: Seventy-nine patients with SLE and 27 healthy controls were included into the study. Serum BAFF and APRIL levels were measured by using ELISA. In 19 patients with active disease at the time of the assessment, BAFF/APRIL levels were reassessed after 6 months of follow-up and disease activity was evaluated by using SLEDAI-2K. The relationship between renal histopathology index scores and lupus nephritis (LN) classes with serum BAFF/APRIL levels was examined in 16 patients who had recent renal involvement and underwent biopsy during the study. Results: Although both BAFF/APRIL levels were higher in patients with SLE compared to the control group (p < 0.001), no correlation was found between BAFF/APRIL levels and SLEDAI scores. Serum BAFF levels were higher in patients with renal disease activity (p = 0.01), and there was a significant correlation between APRIL levels and proteinuria (r = 0.42, p = 0.02). A weak inverse correlation was observed between BAFF and C3 levels (r = 0.25, p = 0.02). No correlation was found between BAFF/APRIL levels and renal SLEDAI scores, renal histopathology, activity, and chronicity index scores. In the active disease group after treatment, there was no significant change in serum BAFF levels, but a significant increase in serum APRIL levels was observed. Conclusion: These results suggest that both cytokines are involved in the pathogenesis of SLE and that serum BAFF can be valuable as a biomarker in SLE especially in patients with renal activity. [ABSTRACT FROM AUTHOR]