To perform a deep dissection of the role and regulation of innate and adaptive immunity in poorly controlled (PC) and well controlled (WC) focal epilepsy.

Individuals with focal epilepsy were prospectively recruited from Brigham and Women’s Hospital outpatient epilepsy clinics. Epilepsy subjects were divided into a WC or PC group based on whether they had seizures within the 6 months prior to study enrollment. Age- and sex-matched healthy controls were also included. Using peripheral blood mononuclear cells (PBMCs), we performed a detailed analysis of ~84,000 PBMCs using single-cell RNA and T-cell receptor sequencing (scRNA/TCR-seq).

A total of 107 subjects were recruited including 87 epilepsy subjects and 20 healthy controls. 49.5% of epilepsy subjects had a seizure within 6 months of recruitment, and 52% had an MRI abnormality. scRNA/TCR-seq data highlighted differences in the composition of adaptive and innate immune cells in well-controlled and poorly-controlled subjects. In particular, memory CD4+ and CD8+ T-cells as well as NK T-cells that express cytotoxic cytokines such as granzyme and perforin, constitute a higher proportion of T-cells in PC epilepsy subjects, whereas CD14+ and CD16+ monocytes, and B memory cells show depletion. Moreover, ligand/receptor network analyses using the CellChat computational tool identified several statistically significant intercellular interactions such as the Selectin cell adhesion pathway that is involved in the recruitment of leukocytes to the site of injury in the brain.

We identified disrupted adaptive and innate immune homeostasis in poorly controlled focal epilepsy. Network analyses revealed ligand/receptor pairs with well-known roles in lymphocyte trafficking that may be targeted for immunomodulatory interventions to treat  epilepsy.