Multiple Sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS) and CD8 T-cells are the predominant T-cell population in MS lesions. Given that transfer of CNS-specific CD8 T-cells results in an attenuated clinical demyelinating disease in C57BL/6 mice with immunization-induced experimental autoimmune encephalomyelitis (EAE), we investigated the cellular target(s) and mechanism(s) of autoreactive regulatory CD8 T-cells. We now report that myelin oligodendrocyte glycoprotein peptide (MOG35–55)-induced CD8 T-cells could also attenuate adoptively transferred, CD4 T-cell-mediated EAE. Whereas CD8−/− mice exhibited more severe EAE associated with increased autoreactivity and inflammatory cytokine production by myelin-specific CD4 T-cells, this was reversed by adoptive transfer of MOG-specific CD8 T-cells. These autoregulatory CD8 T-cells required in vivo MHC Class Ia (KbDb) presentation. Interestingly, MOG-specific CD8 T-cells could also suppress adoptively-induced disease using wildtype MOG35–55-specific CD4 T-cells transferred into KbDb−/− recipient mice, suggesting direct targeting of encephalitogenic CD4 T-cells. In vivo trafficking analysis revealed that autoregulatory CD8 T-cells are dependent on neuro-inflammation for CNS infiltration and their suppression/cytotoxicity of MOG-specific CD4 T-cells is observed both in the periphery and in the CNS. These studies provide important insights into the mechanism of disease suppression mediated by autoreactive CD8 T-cells in EAE.

Our findings suggest that the RNA nuclear foci are pathognomonic for CTG18.1 expansion-mediated endothelial disease. The RNA nuclear foci have been previously found only in rare neurodegenerative disorders caused by repeat expansions. Our detection of abundant ribonuclear foci in FECD implicates a role for toxic RNA in this common disease.

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.

IL-17A is a pro-inflammatory cytokine that has received attention for its role in the pathogenesis of several autoimmune diseases. IL-17A has also been implicated in cardiac and renal allograft rejection. Accordingly, we hypothesized that depletion of IL-17A would enhance corneal allograft survival. Instead, our results demonstrate that blocking IL-17A in a mouse model of keratoplasty accelerated the tempo and increased the incidence of allograft rejection from 50% to 90%. We describe a novel mechanism by which CD4+CD25+ T regulatory cells (Tregs) respond to IL-17A and enhance corneal allograft survival. Our findings suggest that: 1) IL-17A is necessary for ocular immune privilege; 2) IL-17A is not required for the induction of anterior chamber-associated immune deviation (ACAID); 3) Tregs require IL-17A to mediate a contact-dependent suppression; 4) corneal allograft Tregs suppress the efferent arm of the immune response and are antigen-specific; 5) Tregs are not required for corneal allograft survival beyond day 30; and 6) corneal allograft-induced Treg-mediated suppression is transient. Our findings identify IL-17A as a cytokine essential for the maintenance of corneal immune privilege and establish a new paradigm whereby interplay between IL-17A and CD4+CD25+ Tregs is necessary for survival of corneal allografts.

Aquatic photosynthetic organisms such as the green alga Chlamydomonas reinhardtii respond to low-CO(2) conditions by inducing a CO(2) concentrating mechanism (CCM). Important components of the CCM are the carbonic anhydrases (CAs), zinc metalloenzymes that catalyze the interconversion of CO(2) and HCO(-)(3). Six CAs have previously been identified in C. reinhardtii. Here, we identify and characterize two additional beta-type CAs. These two CAs are closely related beta-type CAs and have been designated as CAH7 and CAH8. Conceptual translation shows that CAH7 and CAH8 encode proteins of 399 and 333 amino acids, respectively, and they contain targeting sequences. An unusual characteristic of these two CAs is that they have carboxy-terminal extensions containing a hydrophobic sequence. Both these CAs are constitutively expressed at the transcript and protein level. The CAH7 and CAH8 open reading frames were cloned in the overexpression vector pMal-c2x and expressed as recombinant proteins. Activity assays showed that CAH7 and CAH8 are both active CAs. Antibodies were raised against both CAH7 and CAH8, and immunolocalization studies showed that CAH8 was localized in the periplasmic space. A possible role for CAH8 in the inorganic carbon acquisition by C. reinhardtii is discussed.

Corneal allograft rejection has been described as a Th1-mediated process involving IFN-γ production. However, it has been reported that corneal allograft rejection soars in IFN-γ−/− mice or mice treated with anti–IFN-γ mAb. Th17 is a recently described IL-17A–producing Th cell population that has been linked to renal and cardiac graft rejection, which was originally thought to be Th1-mediated. We tested the hypothesis that Th17 cells mediate corneal allograft rejection in an IL-17A–dependent fashion and unexpectedly found that depletion of IL-17A increased the incidence of rejection to 90%. We demonstrate that the exacerbated rejection following depletion of IL-17A did not result from a loss of cross-regulation of Th1 cells or exaggerated delayed-type hypersensitivity responses. Instead, inhibition of the Th1 or Th17 cell lineages promoted the emergence of a Th2 cell subset that independently mediated allograft rejection. These findings demonstrate that IL-17A is not required for corneal allograft rejection and may instead contribute to the immune privilege of corneal allografts.

Although orthotopic corneal allografts are strategically located for the induction of ACAID by the sloughing of corneal cells into the AC, the results reported here indicate that the Tregs induced by orthotopic corneal allografts are remarkably different from the Tregs that are induced by AC injection of alloantigen. Although both of these Treg populations promote corneal allograft survival, they display distinctly different phenotypes.

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.