Aire mediates tolerance to insulin through thymic trimming of high-affinity T cell clones.

Insulin is a central autoantigen in the pathogenesis of T1D, and thymic epithelial cell expression of insulin under the control of the Autoimmune Regulator () is thought to be a key component of maintaining tolerance to insulin. In spite of this general working model, direct detection of this thymic selection on insulin-specific T cells has been somewhat elusive. Here, we used a combination of highly sensitive T cell receptor transgenic models for detecting thymic selection and sorting and sequencing of Insulin-specific CD4+ T cells from Aire-deficient mice as a strategy to further define their selection.

Correction: Crystal structures of human procathepsin H.

[This corrects the article DOI: 10.1371/journal.pone.

Crystal structures of human procathepsin H.

Cathepsin H is a member of the papain superfamily of lysosomal cysteine proteases. It is the only known aminopeptidase in the family and is reported to be involved in cancer and other major diseases. Like many other proteases, it is synthesized as an inactive proenzyme.

Transfer of Cell-Surface Antigens by Scavenger Receptor CD36 Promotes Thymic Regulatory T Cell Receptor Repertoire Development and Allo-tolerance.

The development of T cell tolerance in the thymus requires the presentation of host proteins by multiple antigen-presenting cell (APC) types. However, the importance of transferring host antigens from transcription factor AIRE-dependent medullary thymic epithelial cells (mTECs) to bone marrow (BM) APCs is unknown. We report that antigen was primarily transferred from mTECs to CD8α dendritic cells (DCs) and showed that CD36, a scavenger receptor selectively expressed on CD8α DCs, mediated the transfer of cell-surface, but not cytoplasmic, antigens.

Revealing the specificity of regulatory T cells in murine autoimmune diabetes.

Regulatory T cells (Tregs) control organ-specific autoimmunity in a tissue antigen-specific manner, yet little is known about their specificity in a natural repertoire. In this study, we used the nonobese diabetic (NOD) mouse model of autoimmune diabetes to investigate the antigen specificity of Tregs present in the inflamed tissue, the islets of Langerhans. Compared with Tregs present in spleen and lymph node, Tregs in the islets showed evidence of antigen stimulation that correlated with higher proliferation and expression of activation markers CD103, ICOS, and TIGIT.

Tolerance is established in polyclonal CD4(+) T cells by distinct mechanisms, according to self-peptide expression patterns.

Studies of repertoires of mouse monoclonal CD4(+) T cells have revealed several mechanisms of self-tolerance; however, which mechanisms operate in normal repertoires is unclear. Here we studied polyclonal CD4(+) T cells specific for green fluorescent protein expressed in various organs, which allowed us to determine the effects of specific expression patterns on the same epitope-specific T cells. Peptides presented uniformly by thymic antigen-presenting cells were tolerated by clonal deletion, whereas peptides excluded from the thymus were ignored.

Spontaneous mutation of the Dock2 gene in Irf5-/- mice complicates interpretation of type I interferon production and antibody responses.

Genome-wide studies have identified associations between polymorphisms in the IFN regulatory factor-5 (Irf5) gene and a variety of human autoimmune diseases. Its functional role in disease pathogenesis, however, remains unclear, as studies in Irf5(-/-) mice have reached disparate conclusions regarding the importance of this transcription factor in type I IFN production and antibody responses. We identified a spontaneous genomic duplication and frameshift mutation in the guanine exchange factor dedicator of cytokinesis 2 (Dock2) that has arisen in at least a subset of circulating Irf5(-/-) mice and inadvertently been bred to homozygosity.

Memory B cells, but not long-lived plasma cells, possess antigen specificities for viral escape mutants.

Memory B cells (MBCs) and long-lived plasma cells (LLPCs) persist after clearance of infection, yet the specific and nonredundant role MBCs play in subsequent protection is unclear. After resolution of West Nile virus infection in mice, we demonstrate that LLPCs were specific for a single dominant neutralizing epitope, such that immune serum poorly inhibited a variant virus that encoded a mutation at this critical epitope. In contrast, a large fraction of MBC produced antibody that recognized both wild-type (WT) and mutant viral epitopes.

Tregs control the development of symptomatic West Nile virus infection in humans and mice.

West Nile virus (WNV) causes asymptomatic infection in most humans, but for undefined reasons, approximately 20% of immunocompetent individuals develop West Nile fever, a potentially debilitating febrile illness, and approximately 1% develop neuroinvasive disease syndromes. Notably, since its emergence in 1999, WNV has become the leading cause of epidemic viral encephalitis in North America. We hypothesized that CD4+ Tregs might be differentially regulated in subjects with symptomatic compared with those with asymptomatic WNV infection.

Batf3 deficiency reveals a critical role for CD8alpha+ dendritic cells in cytotoxic T cell immunity.

Although in vitro observations suggest that cross-presentation of antigens is mediated primarily by CD8alpha+ dendritic cells, in vivo analysis has been hampered by the lack of systems that selectively eliminate this cell lineage. We show that deletion of the transcription factor Batf3 ablated development of CD8alpha+ dendritic cells, allowing us to examine their role in immunity in vivo. Dendritic cells from Batf3-/- mice were defective in cross-presentation, and Batf3-/- mice lacked virus-specific CD8+ T cell responses to West Nile virus.

Early B-cell activation after West Nile virus infection requires alpha/beta interferon but not antigen receptor signaling.

The B-cell response against West Nile virus (WNV), an encephalitic Flavivirus of global concern, is critical to controlling central nervous system dissemination and neurological sequelae, including death. Here, using a well-characterized mouse model of WNV infection, we examine the factors that govern early B-cell activation. Subcutaneous inoculation with a low dose of replicating WNV results in extensive B-cell activation in the draining lymph node (LN) within days of infection as judged by upregulation of the surface markers CD69, class II major histocompatibility complex, and CD86 on CD19(+) cells.

Tumor necrosis factor alpha protects against lethal West Nile virus infection by promoting trafficking of mononuclear leukocytes into the central nervous system.

West Nile virus (WNV) is a neurotropic flavivirus that has emerged globally as a significant cause of viral encephalitis in humans, especially in immunocompromised individuals. Previous studies have shown essential protective roles for antiviral cytokines (e.g.

Type- and subcomplex-specific neutralizing antibodies against domain III of dengue virus type 2 envelope protein recognize adjacent epitopes.

Neutralization of flaviviruses in vivo correlates with the development of an antibody response against the viral envelope (E) protein. Previous studies demonstrated that monoclonal antibodies (MAbs) against an epitope on the lateral ridge of domain III (DIII) of the West Nile virus (WNV) E protein strongly protect against infection in animals. Based on X-ray crystallography and sequence analysis, an analogous type-specific neutralizing epitope for individual serotypes of the related flavivirus dengue virus (DENV) was hypothesized.

Antigen-specific cytotoxic T lymphocytes protect against lethal West Nile virus encephalitis.

Infection with West Nile virus (WNV) causes fatal encephalitis in immunocompromised animals. Previous studies in mice have established that T cell protection is required for clearance of WNV infection from tissues and preventing viral persistence. The current study assessed whether specific WNV peptide epitopes could elicit a cytotoxic T lymphocyte (CTL) response capable of protecting against virus infection.

General deoxyribozyme-catalyzed synthesis of native 3'-5' RNA linkages.

An elusive goal for nucleic acid enzymology has been deoxyribozymes that ligate RNA rapidly, sequence-generally, with formation of native 3'-5' linkages, and in preparatively useful yield. Using in vitro selection, we have identified Mg2+- and Zn2+-dependent deoxyribozymes that simultaneously fulfill all four of these criteria. The new deoxyribozymes operate under practical incubation conditions and have modest RNA substrate sequence requirements, specifically D downward arrowRA for 9DB1 and A downward arrowR for 7DE5 (D = A, G, or U; R = A or G).

Zn2+-dependent deoxyribozymes that form natural and unnatural RNA linkages.

We report Zn(2+)-dependent deoxyribozymes that ligate RNA. The DNA enzymes were identified by in vitro selection and ligate RNA with k(obs) up to 0.5 min(-)(1) at 1 mM Zn(2+) and 23 degrees C, pH 7.