Distinct T Cell Dysregulation Reflects Disease Severity and Progression in Infantile Epileptic Spasms Syndrome and Lennox-Gastaut Syndrome.

Developmental and epileptic encephalopathies (DEEs), including Infantile Epileptic Spasms Syndrome (IESS) and Lennox-Gastaut Syndrome (LGS), are severe pediatric conditions characterized by profound developmental delays and treatment-resistant epilepsy. Although steroid therapies provide some clinical benefits, the underlying immunological mechanisms remain poorly understood. In this study, we performed comprehensive immune profiling using multi-parametric flow cytometry on PBMCs from IESS (n=25) and LGS (n=9) patients, comparing them with age-matched healthy controls (n=54). Our findings identified distinct patterns of immune dysregulation: IESS patients exhibited reduced naïve CD4⁺ T cells, an altered CD4/CD8 ratio, and diminished TNFα production in CD4⁺ T cells. Conversely, LGS patients demonstrated an increase in central memory CD4⁺ T cells, marked dysfunction of Tregs, and heightened activation of CD8⁺ T cells. Notably, elevated activated CD8⁺ T cells in IESS patients correlated significantly with clinical severity and demonstrated enhanced responsiveness to viral peptides, suggesting prior viral infections may exacerbate disease progression. Collectively, our findings demonstrate distinct immune signatures associated with disease severity and progression in DEE, suggesting their potential utility as biomarkers. Further studies are necessary to determine whether targeting these immune pathways could provide clinical benefits.