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Objective: Direct pathogenic effects of autoantibodies to the 65 kDa isoform of glutamic acid decarboxylase (GAD65) in autoimmune limbic encephalitis (LE) have been questioned due to its intracellular localization. We therefore hypothesized a pathogenic role for T cells. Methods: We assessed magnet resonance imaging, neuropsychological and peripheral blood, and CSF flow cytometry data of 10 patients with long‐standing GAD65‐LE compared to controls in a cross‐sectional manner. These data were related to each other within the GAD65‐LE group and linked to neuropathological findings in selective hippocampectomy specimen from another two patients. In addition, full‐resolution human leukocyte antigen (HLA) genotyping of all patients was performed. Results: Compared to controls, no alteration in hippocampal volume but impaired memory function and elevated fractions of activated HLADR+ CD4+ and CD8+ T cells in peripheral blood and cerebrospinal fluid were found. Intrathecal fractions of CD8+ T cells negatively correlated with hippocampal volume and memory function, whereas the opposite was true for CD4+ T cells. Consistently, antigen‐experienced CD8+ T cells expressed increased levels of the cytotoxic effector molecule perforin in peripheral blood, and perforin‐expressing CD8+ T cells were found attached mainly to small interneurons but also to large principal neurons together with wide‐spread hippocampal neurodegeneration. 6/10 LE patients harbored the HLA‐A*02:01 allele known to present the immunodominant GAD65114–123 peptide in humans. Interpretation: Our data suggest a pathogenic effect of CD8+ T cells and a regulatory effect of CD4+ T cells in patients with long‐standing GAD65‐LE. [ABSTRACT FROM AUTHOR]

Inflammation plays a role in the pathogenesis of immune‐mediated epilepsy, but also in epilepsy of other etiology such as hippocampal sclerosis. This study aimed to characterize immune cell signatures in the peripheral blood (PB) and cerebrospinal fluid (CSF) in temporal lobe epilepsy (TLE) of different etiologies. We retrospectively evaluated CSF routine parameters and immune cell profiles using flow cytometry in a cohort of 51 patients and 45 age‐matched controls with functional disorders. Groups were comprised of patients with nonlesional TLE (n = 26), TLE due to hippocampal sclerosis (n = 14), or limbic encephalitis with antibodies against the 65‐kDa isoform of glutamic acid decarboxylase (GAD65‐LE; n = 11). TLE patients showed increased proportions of human leukocyte antigen–DR isotype (HLA‐DR)‐expressing CD4+ T lymphocytes in the CSF. Furthermore, they were characterized by a shift in monocyte subsets toward immature CD14lowCD16+ cells in the PB and blood/CSF‐barrier dysfunction. Whereas TLE patients in general showed similar immune cell profiles, patients with GAD65‐LE differed from other TLE patients by increased proportions of HLA‐DR–expressing CD8+ T lymphocytes and type 2/3 oligoclonal bands. These findings point to a role of innate and adaptive immunity in TLE. CSF parameters may help to discriminate epilepsy patients from controls and different forms of TLE from each other. [ABSTRACT FROM AUTHOR]

Objective HIV-associated neurocognitive disorders ( HAND) remain a challenge despite combination antiretroviral therapy ( cART). Immune cell activation has been implicated to play a major role in the development of HAND. Methods In this study, we used multicolor flow cytometry on peripheral blood ( PB) and cerebrospinal fluid ( CSF) samples to determine the expression of HLA- DR and programmed death-1 ( PD-1) on CD4+ and CD8+ T cells in patients with chronic HIV infection. Expression levels were correlated with HI virus load in PB and CSF, classification of HAND and severity of magnetic resonance imaging ( MRI) signal abnormalities. Results In a cohort of 86 HIV patients we found that the grade of neurocognitive impairment and the severity of MRI signal abnormalities correlated with decreasing CD4/ CD8-ratios and increased frequencies of HLA- DR expressing CD4+ and CD8+ T cells reaching the highest values in the CSF samples. Importantly, HLA- DR upregulation was still detectable in virologically suppressed HIV patients. Further, T-cell subpopulation analysis of 40 HIV patients showed a significant shift from naïve to effector memory ( EM) T cells that was negatively correlated with the grade of neurocognitive impairment in the PB samples. Moreover, PD-1 was significantly increased on CD4+ memory T cells with highest levels on EM T cells in HIV patients with mild or severe neurocognitive alterations. Interpretation The CD4/ CD8 ratio, the proportion of EM to naïve T cells and the immune activation profile of CD4+ and CD8+ T cells in PB and CSF might be useful parameters to monitor the efficacy of cART and to identify HIV patients at risk of further neurocognitive deterioration. [ABSTRACT FROM AUTHOR]