Investigation of TL1A,IL-17,IL-22,IL-13,IL-4,IL-11,IL-34,IL-9,TGF-beta levels at serum and tissue in hidradenitis suppurativa patients

Investigation of Serum and Tissue Levels of TL1A, IL-17, IL-22, IL-13, IL-4, IL-11, IL-34, IL-9, and TGF-β in Hidradenitis Suppurativa Patients Hidradenitis suppurativa (HS) is a multifactorial disease characterized by deep- seated, painful nodules, draining abscesses, and sinus tracts affecting the skin and subcutaneous tissues. It predominantly occurs in young individuals aged 18-34 years. The most commonly affected sites include the gluteal region, groin, axillae, anogenital area, and scalp. The pathogenesis of HS is complex, with follicular occlusion being considered the initial trigger, leading to inflammation and cytokine release. The role of cytokines such as TNF-α and IL-17 has been demonstrated in multiple studies. TL1A (TNFSF15) is known to play a role in various inflammatory processes and has been reported to be elevated in inflammatory diseases such as Crohn's disease and psoriasis, which share pathogenetic similarities with HS. Inspired by these findings, our study aimed to evaluate the serum levels and tissue expression (lesional and perilesional) of TL1A, IL-17, IL-22, IL-13, IL-4, IL-11, IL-34, IL-9, and TGF-β in HS patients and their correlation with disease severity and inflammatory parameters. Our study included 25 HS patients and 25 healthy volunteers. Serum cytokine levels were measured using ELISA, and expression analysis was performed on tissue samples. Body mass index, waist circumference, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), routine biochemistry, and lipid parameters were recorded in both groups. No significant difference was found in serum TL1A levels between HS patients and healthy controls. However, TL1A expression was higher in perilesional tissue than in lesional tissue. Increased serum TL1A levels were associated with higher IL-17, IL- 22, IL-13, and IL-9 expression in lesional skin. Serum IL-17, IL-22, and TGF-β levels were significantly elevated in HS patients, whereas IL-9, IL-11, IL-13, and IL-34 showed no significant difference between groups. Serum IL-4 levels were significantly lower in HS patients. In lesional tissue, the expression of IL-11, IL-13, IL-17, IL-22, IL-34, IL-4, IL-9, and TL1A was lower than in perilesional tissue, whereas TGF-β expression was higher. Serum IL-22 showed a negative correlation with lesional TL1A, IL-17, IL-22, and IL-11, and a significant correlation with neutrophil-to- lymphocyte ratio (NLR). Additionally, IL-22 negatively correlated with TL1A, and 82 only IL-22 was significantly correlated with Hurley staging. Serum CRP correlated with IHS4, while serum TGF-β correlated significantly with disease severity. Our findings contribute to the understanding of HS pathogenesis, suggesting that further research may clarify the role of these cytokines and their potential therapeutic implications in HS treatment. Key Words: TL1A, Hidradenitis Suppurativa, IL-4, IL-13, IL-34