Altered Stool Cytokine Profiles and Pro-Inflammatory/Anti-Inflammatory Imbalance in Children with Autism Spectrum...

Background: Immune dysregulation and gut dysbiosis are increasingly implicated in autism spectrum disorder (ASD), but compartment-specific intestinal cytokine profiles remain poorly defined. Aim: To characterize stool cytokine profiles and pro-/anti-inflammatory balance in children with ASD across development. Methods: We analyzed stool samples from 283 children (109 controls, 104 mild ASD, 70 severe ASD; age 0.9-21.5 years) recruited at a tertiary centre. Nine cytokines (IFN-γ, IL-1α, IL-1β, IL-4, IL-6, IL-8, IL-10, IL-17, TNF-α) were measured using a Luminex multi-plex assay; IL-15 was excluded due to >70% missing values. Group comparisons used Mann-Whitney U tests, with age stratification at the cohort median (≤9.5 vs. >9.5 years). A composite pro-/anti-inflammatory ratio (IL-1α + IL-1β + IL-6 + IL-8 + IL-17 + TNF-α + IFN-γ divided by IL-4 + IL-10) was calculated. Results: In the overall cohort, stool IL-8 and IL-4 were significantly decreased in ASD versus controls (IL-8: median 0.36 vs. 0.49 ng/L, p = 0.0041; IL-4: 0.28 vs. 0.30 ng/L, p = 0.0316), with a graded reduction from controls to mild and severe ASD. Age-stratified analysis revealed that IL-8 reduction was confined to younger children (≤9.5 years; p = 0.0025) and absent in older children, while IL-1β was significantly reduced in younger ASD children and tended to reverse in older ASD children. The pro-/anti-inflammatory ratio was markedly elevated in severe ASD (median 491 vs. 209 in controls; p = 0.059), particularly in older children. Stool IL-8 and IL-1β correlated inversely with CARS scores within the ASD group. Conclusions: Children with ASD show decreased stool IL-8 and IL-4 and a shift toward a pro-inflammatory cytokine balance, with the strongest alterations during early childhood. These findings are consistent with the hypothesis of a developmental window of intestinal immune dysregulation in ASD, with stool IL-8 as the primary FDR-corrected finding. The present cross-sectional data do not establish causality and independent replication is required before clinical conclusions are drawn.