Stroke induction in immunologically competent mice not only produces local ischemia and brain damage, but also induces early inflammatory changes in brain and peripheral immune responses. Although immune elements clearly are activated after brain vascular occlusion, the relative contribution of T and B lymphocytes to the developing lesion has not been quantified. We evaluated effects 22 h after middle cerebral artery occlusion (90 mins) on histologic injury and peripheral immune activation in severe combined immunodeficient (SCID) mice lacking T and B cells. Cortical and total infarct volumes were strikingly reduced in male SCID mice (n = 14, 3364% of contralateral cortex, n = 10, 5263% of contralateral hemisphere) versus immunologically intact C57BL/6 mice (wild type, n = 9, 5765% of contralateral cortex, 5764% of contralateral hemisphere) (P < 0.01). Striatal infarction was not altered (7767% of contralateral striatum in SCID, 8467% in wild type), suggesting that the core of the evolving ischemic lesion was not impacted by lack of T and B cells. As expected, inflammatory factors from immune cells in ischemic SCID brains were essentially absent, with the exception of interleukin-1b increase in both SCID and wild type tissue. Spleen cell numbers were low in SCID mice, but were further reduced 22 h after stroke, with substantial reduction in most inflammatory factors except for increased expression of interferon-c and macrophage inflammatory protein (MIP)-2. These data quantify the damaging effect of T and B lymphocytes on early, evolving ischemic brain injury, and further implicate interleukin-1b in brain and interferon-c and MIP-2 in spleen as inflammatory factors produced by cells other than T and B cells.

Although estrogens exert a pronounced protective effect on multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), their therapeutic application has been limited by undesirable side effects thought to be mediated primarily through estradiol binding to intracellular estrogen receptor α. In this study, we found that signaling through the putative membrane estrogen receptor, G protein-coupled receptor 30 (GPR30), was sufficient to mediate protection against EAE, which was significantly impaired in GPR30 gene-deficient mice. Treatment with G-1, an agonist that selectively activates GPR30 without engagement of the intracellular estrogen receptors, retained the ability of estradiol to protect against clinical and histological EAE without estradiol-associated side effects, deviated cytokine profiles, and enhanced suppressive activity of CD4+Foxp3+ T regulatory cells through a GPR30- and programmed death 1-dependent mechanism. This study is the first to evaluate the protective effect of GPR30 activation on EAE, and provides a strong foundation for the clinical application of GPR30 agonists such as G-1 in multiple sclerosis.

Summary The mechanism by which oestrogens suppress experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, is only partially understood. We here demonstrate that treatment with 17β‐oestradiol (E2) in C57BL/6 mice boosted the expression of programmed death 1 (PD‐1), a negative regulator of immune responses, in the CD4+ FoxP3+ regulatory T (Treg) cell compartment in a dose‐dependent manner that correlated with the efficiency of EAE protection. Administration of E2 at pregnancy levels but not lower concentrations also enhanced the frequency of Treg cells. Additionally, E2 treatment drastically reduced the production of interleukin‐17 (IL‐17) in the periphery of immunized mice. However, E2 treatment did not protect against EAE or suppress IL‐17 production in PD‐1 gene‐deficient mice. Finally, E2 failed to prevent Treg‐deficient mice from developing spontaneous EAE. Taken together, our results suggest that E2‐induced protection against EAE is mediated by upregulation of PD‐1 expression within the Treg‐cell compartment.

Recombinant T-cell receptor ligands (RTLs) can prevent and reverse clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in an antigen

Inflammation results in CNS damage in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), an animal model of MS. It is uncertain how much repair of injured myelin and axons can occur following highly selective anti-inflammatory therapy in EAE and MS. In this study, SJL/J mice with established EAE were treated successfully with an antigen-specific recombinant T cell receptor ligand (RTL), RTL401, a mouse I-A s /PLP-139-151 construct, after the peak of EAE. To define the mechanisms by which late application of RTL401 inhibits EAE, we evaluated mice at different time points to assess the levels of neuroinflammation and myelin and axon damage in their spinal cords. Our results showed that RTL401 administered after the peak of acute EAE induced a marked reduction in inflammation in the CNS, associated with a significant reduction of demyelination, axonal loss and ongoing damage. Electron microscopy showed that RTL-treated mice had reduced pathology compared with mice treated with vehicle and mice at the peak of disease, as demonstrated by a decrease in continued degeneration, increase in remyelinating axons and the presence of an increased number of small, presumably regenerative axonal sprouts. These findings indicate that RTL therapy targeting encephalitogenic T cells may promote CNS neuroregenerative processes. Keywords: axonal loss, demyelination, multiple sclerosis, T lymphocytes. The early inflammatory phase of multiple sclerosis (MS) is believed to involve an autoimmune process similar to that induced in experimental autoimmune encephalomyelitis (EAE) upon immunization with myelin antigens in adjuvants. In both instances it is apparent that encephalitogenic T cells penetrate the blood-brain barrier and cause neuroinflammation, demyelination and axonal damage in the CNS (Steinman 1996). Clinically, MS has a very diverse clinical presentation and course, with a majority of MS patients experiencing a relapsing-remitting phase (RRMS) that may evolve into a secondary progressive phase (SPMS) characterized by persistent and advancing neurological impairments. In primary progressive MS (PPMS), the symptoms are progressive from onset without remissions. Collective evidence suggests axonal loss occurs at all stages of MS and is responsible for the accrual of disability in progressive MS.Development of effective treatments aimed at preventing or restoring CNS myelin and axonal damage is crucial for successful management of MS. Current therapies such as glatiramer acetate and recombinant, B-interferons can reduce MRI enhancing lesions and slow clinical progression of MS, but little is known about the effects of these therapies on myelin and axonal injury. Moreover, although blockade of immune cell trafficking into the CNS with anti-VLA-4 antibodies (Natalizumab) appears to effectively reduce CNS inflammation, this therapeutic approach can cause lifethreatening complications, such as progressive multifocal leucoencephalopathy (Lublin 2005), and may inhibit the