Background: Anti-N-Methyl-d-aspartate receptor (NMDAR) autoimmune encephalitis (NMDAR AE) is an autoimmune disease characterized by severe psychiatric and neurological symptoms. While the pathogenic role of antibodies (Abs) directed against the GluN1 subunit of NMDAR is well described in this disease, the immune mechanisms involved in the generation of the autoimmune B cell response, especially the role of T helper cells, are poorly understood. Previously, we developed a B-cell-mediated mouse model of NMDAR AE by immunization with a GluN1_359–378 peptide that drives a series of symptoms that recapitulate AE such as anxiety behaviour and spatial memory impairment. Results: In this mouse model, we identified anti-GluN1-specific CD4⁺ but also CD8⁺ T cells in both spleen and meninges. T helper cells have a polyfunctional profile, arguing for a T and B cell crosstalk to generate anti-GluN1 pathogenic Abs. Interestingly, proteomic analysis of AE meninges showed enrichment of differentially expressed proteins in biological processes associated with B cell activation and cytokine signalling pathways. Conclusions: This study identified, for the first time, a potential contribution of T helper cells in the pathology of NMDAR AE and paved the way for the development of future tolerogenic approaches to treat relapses.

Anorexia nervosa (AN) is a debilitating, often lethal, restrictive-type eating disorder without an effective cure. The underlying neural basis of AN has remained elusive without an animal model that has represented all typical AN symptoms. Here we show that aberrant activation of mediobasal hypothalamic (MBH) glutamatergic neurons led to lethal self-starvation, hyperactivity, anhedonia, social phobia, and increased anxiety, all of which represent typical symptoms of AN. These symptoms were selectively exhibited by targeted activation of MBH neurons expressing steroidogenic factor (SF1) and estrogen receptor alpha (ERa). Moreover, the elicited AN symptoms by activation of MBH glutamatergic or SF1/ERa neurons were rescued by removing release of glutamate or brain-derived neurotrophic factor (BDNF) from these neurons. Importantly, BDNF overexpression in SF1/ERa neurons promoted typical AN symptoms, which were suppressed by removing glutamate release. Thus, our findings identify aberrantly enhanced BDNF and consequent augmented glutamate release from SF1/ERa neurons as a neural basis underlying AN.