Pathogenic and Clinical Relevance of Serum IL-17A and TNF-α in Systemic Lupus Erythematosus

Cytokines IL-17A and TNF-α have been implicated in the dysregulated immune responses that characterize SLE, with potential relevance to specific organ involvement. This study aimed to assess their serum levels in SLE patients and to explore potential correlations with clinical, biological, and immunological features, as well as with disease activity and damage scores. We conducted a cross-sectional analysis of 88 SLE patients diagnosed according to the 2012 SLICC classification criteria and 87 controls matched by sex and age. Serum IL-17A and TNF-α levels were quantified using ELISA. Clinical and laboratory data were collected, including SLEDAI for disease activity and the SLICC/ACR Damage Index for cumulative organ damage. No significant differences were observed in serum IL-17A levels between SLE patients and healthy controls, whereas serum TNF-α levels differed significantly between the two groups. Serum IL-17A levels were significantly associated with cutaneous involvement (p = 0.036) and the inflammatory syndrome (p = 0.049). TNF-α levels were also significantly elevated in patients with cutaneous manifestations (p = 0.050). A positive correlation was observed between TNF-α levels and cumulative organ damage, as assessed by the SLICC/ACR Damage Index (r = 0.36, p < 0.001; R² = 0.13), and levels were particularly higher in patients with malignancies (p = 0.032). A positive correlation was observed between IL-17A and TNF-α levels. No significant associations were found between serum levels of IL-17A or TNF-α and demographic factors, disease activity (SLEDAI), immunological and biological markers. Both IL-17A and TNF-α were significantly associated with cutaneous involvement in SLE patients, supporting their implication in skin-related inflammatory processes. IL-17A was additionally linked to the presence of an inflammatory syndrome. TNF-α levels correlated with cumulative organ damage and were elevated in patients with malignancies, suggesting that patients with higher TNF-α accumulated significantly more irreversible organ damage over time. No meaningful associations were observed between cytokine levels and demographic characteristics, disease duration, treatment or global SLE activity.