Evaluation of Plasma Soluble CD 40 Ligand (sCD40L) Levels as a Biomarker for Autism Spectrum Disorder: A Link to the Severity of Cognitive, Social, and Sensory Dysfunctions

Background: Soluble CD40 ligand (sCD40L) plays an important role in inflammation and autoimmune disorders, including a variety of neurological and neurodegenerative disorders. However, evidence regarding the role of sCD40L in autism spectrum disorder (ASD) is limited. Therefore, the aim of this study was to assess the clinical significance of plasma sCD40L levels in individuals with ASD and to examine their relationship with the severity of ASD, social impairments, and sensory dysfunction. Materials and Methods: Plasma levels of sCD40L were measured using an enzyme-linked immunosorbent assay (ELISA). The severity of ASD, social impairments, and sensory dysfunction was assessed in all children with ASD using the Childhood Autism Rating Scale (CARS), the Social Responsiveness Scale (SRS), and the Short Sensory Profile (SSP), respectively. Results: Plasma sCD40L levels were significantly increased in children with ASD (83.77 ± 24.76) compared with controls (68.28 ± 12.74), with p = 0.001. Plasma sCD40L levels were significantly higher in children with severe ASD-related symptoms. The mean sCD40L levels were 87.23 ± 20.93 among children with severe ASD according to the CARS, 86.45 ± 25.53 among those with greater social impairment according to the SRS, and 89.74 ± 27.22 among those with atypical sensory processing according to the SSP (p ≤ 0.05). These results indicate that sCD40L levels increased with greater severity of the symptoms. Additionally, receiver operating characteristic (ROC) curve analysis revealed significant discriminatory ability of plasma sCD40L between the two groups, with an AUC of 0.701 [95% confidence interval (CI), 0.583–0.819, p < 0.001]. Conclusions: Our study suggests that sCD40L may contribute to the pathophysiology of ASD and be associated with the severity of ASD symptoms. This association suggests that sCD40L may serve as a promising biomarker for neuroinflammatory processes associated with ASD. However, further studies with larger sample sizes are warranted to validate these findings.