Flow cytometry analysis of T cell subsets in cerebrospinal fluid and pheriperal blood of narcolepsy type 1 patients with long lasting disease

Background: Type 1 Narcolepsy (NT1) is a central hypersomnia linked to the destruction of hypocretin-producing neurons. A great body of genetic and epidemiological data points to a likely autoimmune disease aetiology. Recent reports have characterized peripheral blood T-cell subsets in NT1, whereas data regarding the cerebrospinal fluid (CSF) immune cell composition are lacking. In this study, we aim to identify the T- and NK- cell subsets in NT1 patients with long-term disease course. Methods: Immune cell subsets from CSF and peripheral blood mononuclear cell (PBMC) samples were analysed by flow cytometry in two age-, sex and BMI-balanced groups of 14 NT1 patients versus 14 healthy controls. The frequency of CSF cell groups were compared with PBMCs. Non-parametric tests were used for statistical analyses. Results: NT1 patients did not show significant differences of CSF immune cell subsets compared to controls, despite a trend towards higher CD4+ terminally differentiated effector memory T cells. T cells preferentially displayed a memory phenotype in the CSF compared to PBMCs. Furthermore, a reduced frequency of CD4+ terminally differentiated effector memory T cells and an increased frequency of Natural Killer CD56bright cells were observed in PBMCs from patients compared to controls. Finally, the ratio between CSF and peripheral CD4+ terminally differentiated effector memory T cells showed a two-fold increase in NT1 patients versus controls. Conclusions: Significant differences in PBMCs and CSF immune cell profile were found between NT1 patients versus controls. These differences may reflect differences in HLA status, or be primary or secondary to hypocretin deficiency in narcolepsy.