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Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS). Although its etiology remains unknown, pathogenic T cells are thought to underlie MS immune pathology. We recently showed that MS patients harbor CNS-specific CD8+ Tregs that are deficient during disease relapse. We now demonstrate that CNS-specific CD8+ Tregs were cytolytic and could eliminate pathogenic CD4+ T cells. These CD8+ Tregs were present primarily in terminally differentiated (CD27-, CD45RO-) subset and their suppression was IFNγ, perforin and granzyme B-dependent. Interestingly, MS patients with acute relapse displayed a significant loss in terminally differentiated CD8+ T cells, with a concurrent loss in expression of perforin and granzyme B. Pre-treatment of exacerbation-derived CD8+ T cells with IL-12 significantly restored suppressive capability of these cells through upregulation of granzyme B. Our studies uncover immune-suppressive mechanisms of CNS-specific CD8+ Tregs, and may contribute to design of novel immune therapies for MS.

Objective: Despite successful endovascular therapy, a proportion of stroke patients exhibit long‐term functional decline, regardless of the cortical reperfusion. Our objective was to evaluate the early activation of the adaptive immune response and its impact on neurological recovery in patients with large vessel occlusion (LVO). Methods: Nineteen (13 females, 6 males) patients with acute LVO were enrolled in a single‐arm prospective cohort study. During endovascular therapy (EVT), blood samples were collected from pre and post‐occlusion, distal femoral artery, and median cubital vein (controls). Cytokines, chemokines, cellular and functional profiles were evaluated with immediate and follow‐up clinical and radiographic parameters, including cognitive performance and functional recovery. Results: In the hyperacute phase (within hours), adaptive immune activation was observed in the post‐occlusion intra‐arterial environment (post). Ischemic vascular tissue had a significant increase in T‐cell‐related cytokines, including IFN‐γ and MMP‐9, while GM‐CSF, IL‐17, TNF‐α, IL‐6, MIP‐1a, and MIP‐1b were decreased. Cellularity analysis revealed an increase in inflammatory IL‐17+ and GM‐CSF+ helper T‐cells, while natural killer (NK), monocytes and B‐cells were decreased. A correlation was observed between hypoperfused tissue, infarct volume, inflammatory helper, and cytotoxic T‐cells. Moreover, helper and cytotoxic T‐cells were also significantly increased in patients with improved motor function at 3 months. Interpretation: We provide evidence of the activation of the inflammatory adaptive immune response during the hyperacute phase and the association of pro‐inflammatory cytokines with greater ischemic tissue and worsening recovery after successful reperfusion. Further characterization of these immune pathways is warranted to test selective immunomodulators during the early stages of stroke rehabilitation. [ABSTRACT FROM AUTHOR]

Individuals with amnestic mild cognitive impairment (aMCI) experience cognitive declines in learning and memory greater than expected for normal aging, and are at a high risk of dementia. We previously reported that sedentary aMCI patients exhibited neuroinflammation that correlated with brain amyloid beta (Aß) burden, as determined by 18F-florbetapir positron emission tomography (PET). These aMCI patients enrolled in a one-year randomized control trial (AETMCI, NCT01146717) to test the beneficial effects of 12 months of moderate-to-high intensity aerobic exercise training (AET) or stretching/toning (ST) control intervention on neurocognitive function. A subset of aMCI participants had PET imaging, cognitive testing, and immunophenotyping of cerebrospinal fluid (CSF) and peripheral blood after AET or ST interventions. As adaptive immune responses were similar between AET and ST groups, we combined AET/ST into a general 'physical activity' (PA) group and compared Aß burden, cognitive function, and adaptive immune cell subsets to sedentary lifestyle before intervention. We found that PAinduced immunomodulation of CD4+ and CD8+ T cells in CSF correlated with changes in Aß burden in brain regions associated with executive function. Furthermore, after PA, cognitive scores on tests of memory, processing speed, attention, verbal fluency, and executive function were associated with increased percent representation of circulating naïve B cells and CD8+ T cells. We review the literature on aMCIrelated cognition and immune changes as they relate to exercise, and highlight how our preliminary data suggest a complex interplay between the adaptive immune system, physical activity, cognition, and Aß burden in aMCI. [ABSTRACT FROM AUTHOR]

The autoimmune disease systemic lupus erythematosus is characterized by loss of tolerance to nuclear Ags and a heightened inflammatory environment, which together result in end organ damage. Lyn-deficient mice, a model of systemic lupus erythematosus, lack an inhibitor of B-cell and myeloid cell activation. This results in B-cell hyper-responsiveness, plasma cell accumulation, autoantibodies, and glomerulonephritis (GN). IL-21 is associated with autoimmunity in mice and humans and promotes B-cell differentiation and class switching. Here, we explore the role of IL-21 in the autoimmune phenotypes of lyn-/- mice. We find that IL-21 mRNA is reduced in the spleens of lyn-/-IL-6-/- and lyn-/-Btklo mice, neither of which produce pathogenic autoantibodies or develop significant GN. While IL-21 is dispensable for plasma cell accumulation and IgM autoantibodies in lyn-/- mice, it is required for anti-DNA IgG antibodies and some aspects of T-cell activation. Surprisingly, GN still develops in lyn-/-IL-21-/- mice. This likely results from the presence of IgG autoantibodies against a limited set of non-DNA Ags. These studies identify a specific role for IL-21 in the class switching of anti-DNA B cells and demonstrate that neither IL-21 nor anti-DNA IgG is required for kidney damage in lyn-/- mice. [ABSTRACT FROM AUTHOR]

Objective: To determine the antigenic determinants and specific molecular requirements for the generation of autoregulatory neuroantigen-specific CD8(+) T cells in models of multiple sclerosis (MS)., Methods: We have previously shown that MOG35-55-specific CD8(+) T cells suppress experimental autoimmune encephalomyelitis (EAE) in the C57BL/6 model. In this study, we utilized multiple models of EAE to assess the ability to generate autoregulatory CD8(+) T cells., Results: We demonstrate that alternative myelin peptides (PLP178-191) and other susceptible mouse strains (SJL) generated myelin-specific CD8(+) T cells, which were fully capable of suppressing disease. The disease-ameliorating function of these cells was dependent on the specific cognate myelin antigen. Generation of these autoregulatory CD8(+) T cells was not affected by thymic selection, but was dependent on the presence of both CD4(+) and CD8(+) T-cell epitopes in the immunizing encephalitogenic antigen., Conclusions: These studies show that the generation of autoregulatory CD8(+) T cells is a more generalized, antigen-specific phenomenon across multiple neuroantigens and mouse strains, with significant implications in understanding disease regulation.

Stroke affects millions of people worldwide every year. Despite this prevalence, mechanisms of long-term injury and repair within the ischemic brain are still understudied. Sterile inflammation occurs in the injured brain after stroke, with damaged tissue exposing central nervous system (CNS)-derived antigen that could initiate potential autoimmune responses. We used a standard immunology-based recall response assay for murine immune cells, isolated from the cervical lymph nodes and spleen after transient stroke, to determine if stroke induces autoreactivity to CNS target antigens. Our assays included novel neuronal peptides, in addition to myelin-, nuclear-, glial-, and endothelial-derived peptides. Autoimmune responses to an antigen were considered positive based on proliferation and activation over non-stimulated conditions. Stroke induced a significant increase in autoreactive CD4+ and CD8+ T cells, as well as autoreactive CD19+ B cells, as early as 4 days after stroke onset. Mice with large infarct volumes exhibited early T and B cell autoreactivity to NR2A, an NMDA receptor subunit, in cells isolated from lymph nodes but not spleen. Mice with small infarct volumes exhibited high autoreactivity to MAP2, a dendritic cytoskeletal protein, as well as myelin-derived peptides. This autoimmunity was maintained through 10 days post-stroke in both lymph nodes and spleen for all lymphocyte subsets. Sham surgery also induced early autoreactive B cell responses to MAP2 and myelin. Based on these observations, we hypothesize that stroke induces a secondary, complex, and dynamic autoimmune response to neuronal antigens with the potential to potentiate, or perhaps even ameliorate, long-term neuroinflammation.

The immune system plays a major pathological and regulatory role in multiple sclerosis (MS) and, therefore, is a focus of extensive research. Animal models of MS have been crucial in understanding the pathological processes in MS and developing certain treatments, however, all crucial aspects of the human disease may not be appropriately modeled. With the exception of detecting oligoclonal bands and IgG synthesis in cerebrospinal fluids of MS patients, there has not been major progress in the development of immunologic tests that can be used for diagnosis of MS. Further, due to the lack of validated immune assays, routine monitoring of the immune system following therapy initiation is not a part of standard patient care in MS. This is critical since immunomodulatory therapies used for MS treatment are not benign and, more importantly, there is a considerable variation in clinical responses in MS patients initiating such therapies. Flow cytometry is a powerful tool that can be used for studying both the phenotype and function of immune cells. The studies described here will demonstrate how flow cytometry can be used to apply current knowledge about the MS immune system to develop a diagnostic laboratory test for the immunologic monitoring of this disease. Importantly, we will also show that the multiparameter flow cytometry based assay developed by us can also be implemented for the immunologic evaluation of therapeutic success in MS patients.

The autoimmune disease systemic lupus erythematosus is characterized by loss of tolerance to nuclear Ags and a heightened inflammatory environment, which together result in end organ damage. Lyn-deficient mice, a model of systemic lupus erythematosus, lack an inhibitor of B-cell and myeloid cell activation. This results in B-cell hyper-responsiveness, plasma cell accumulation, autoantibodies, and glomerulonephritis (GN). IL-21 is associated with autoimmunity in mice and humans and promotes B-cell differentiation and class switching. Here, we explore the role of IL-21 in the autoimmune phenotypes of lyn(-/-) mice. We find that IL-21 mRNA is reduced in the spleens of lyn(-/-) IL-6(-/-) and lyn(-/-) Btk(lo) mice, neither of which produce pathogenic autoantibodies or develop significant GN. While IL-21 is dispensable for plasma cell accumulation and IgM autoantibodies in lyn(-/-) mice, it is required for anti-DNA IgG antibodies and some aspects of T-cell activation. Surprisingly, GN still develops in lyn(-/-) IL-21(-/-) mice. This likely results from the presence of IgG autoantibodies against a limited set of non-DNA Ags. These studies identify a specific role for IL-21 in the class switching of anti-DNA B cells and demonstrate that neither IL-21 nor anti-DNA IgG is required for kidney damage in lyn(-/-) mice., (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)