Treg Cells Modulate Neuroinflammation and Behavioral Deficits in Autism: Evidence From <scp>MR</scp> ‐Based Genetic Analyses and Experimental Models

Autism spectrum disorder (ASD) is a neurodevelopmental condition that is increasingly linked to immune dysfunction and neuroinflammation. Regulatory T cells (Tregs), which are crucial in maintaining immune homeostasis, have been implicated in the pathogenesis of ASD. However, their role in neuroimmune interactions and behavioral outcomes remains poorly understood. We employed Mendelian Randomization (MR) to assess the causal relationship between Tregs and ASD risk, using genetic data to infer causality. To further confirm the reliability of the MR results, we incorporated data from an independent genome-wide association study (GWAS) and conducted a meta-analysis to strengthen causal inference. Additionally, we validated our findings in an ASD-like mouse model (BTBR mice) treated with the IL-2/JES6.1 complex to enhance Tregs' function. Neuroinflammation and behavioral outcomes were assessed in treated and control mice. MR analysis revealed significant associations between several Tregs subsets and ASD risk. The proportion of CD127^‒ CD8⁺ T cells among total T cells showed a consistent protective effect (OR = 0.84, p = 0.01166), which was validated across multiple analytical methods. The absolute count of resting CD4⁺ regulatory T cells was also inversely associated with ASD risk and demonstrated an independent protective effect in multivariable MR analysis. Sensitivity analyses revealed no evidence of horizontal pleiotropy or heterogeneity. Experimental treatment with IL-2/JES6.1 in BTBR mice significantly increased CD4⁺ Tregs populations, enhanced CD4⁺ Tregs activation, and improved social interactions and repetitive behavior. Furthermore, IL-2/JES6.1 treatment reduced neuroinflammatory markers, including microglial activation. Transcriptomic analysis revealed that IL-2/JES6.1 treatment induced neuroendocrine and synaptic plasticity pathways in the hippocampus and cortex while suppressing inflammatory signaling. This study demonstrates that Tregs modulation can influence ASD pathogenesis through immune regulation and behavioral improvement. Our findings highlight the potential of Treg-targeted therapies for ASD. Future studies should focus on the mechanistic pathways involved and explore the clinical applicability of these therapies.