Fam49b dampens TCR signal strength to regulate survival of positively selected thymocytes and peripheral T cells.

The fate of developing T cells is determined by the strength of T cell receptor (TCR) signal they receive in the thymus. This process is finely regulated through the tuning of positive and negative regulators in thymocytes. The Family with sequence similarity 49 member B (Fam49b) protein is a newly discovered negative regulator of TCR signaling that has been shown to suppress Rac-1 activity in vitro in cultured T cell lines.

The promiscuous development of an unconventional Qa1b-restricted T cell population.

MHC-E restricted CD8 T cells show promise in vaccine settings, but their development and specificity remain poorly understood. Here we focus on a CD8 T cell population reactive to a self-peptide (FL9) bound to mouse MHC-E (Qa-1) that is presented in response to loss of the MHC I processing enzyme ERAAP, termed QFL T cells. We find that mature QFL thymocytes are predominantly CD8αβ+CD4-, show signs of agonist selection, and give rise to both CD8αα and CD8αβ intraepithelial lymphocytes (IEL), as well as memory phenotype CD8αβ T cells.

CD4 T Cell Responses to Are a Double-Edged Sword.

CD4 T cells have been found to play critical roles in the control of both acute and chronic infection. Previous studies identified a protective role for the CD4 T cell-eliciting peptide AS15 (AVEIHRPVPGTAPPS) in C57BL/6J mice. Herein, we found that immunizing mice with AS15 combined with GLA-SE, a TLR-4 agonist in emulsion adjuvant, can be either helpful in protecting male and female mice at early stages against Type I and Type II parasites or harmful (lethal with intestinal, hepatic, and spleen pathology associated with a storm of IL6).

Murine cytomegalovirus downregulates ERAAP and induces an unconventional T cell response to self.

The endoplasmic reticulum aminopeptidase associated with antigen processing (ERAAP) plays a crucial role in shaping the peptide-major histocompatibility complex (MHC) class I repertoire and maintaining immune surveillance. While murine cytomegalovirus (MCMV) has multiple strategies for manipulating the antigen processing pathway to evade immune responses, the host has also developed ways to counter viral immune evasion. In this study, we find that MCMV modulates ERAAP and induces an interferon γ (IFN-γ)-producing CD8 T cell effector response that targets uninfected ERAAP-deficient cells.

The ER Aminopeptidases, ERAP1 and ERAP2, synergize to self-modulate their respective activities.

Introduction: Critical steps in Major Histocompatibility Complex Class I (MHC-I) antigen presentation occur in the endoplasmic reticulum (ER). In general, peptides that enter the ER are longer than the optimal length for MHC-I binding. The final trimming of MHC-I epitopes is performed by two related aminopeptidases, ERAP1 and ERAP2 in humans that possess unique and complementary substrate trimming specificities.

The Role of T Cells in Obesity-Associated Inflammation and Metabolic Disease.

Chronic inflammation plays a critical role in the development of obesity-associated metabolic disorders such as insulin resistance. Obesity alters the microenvironment of adipose tissue and the intestines from anti-inflammatory to pro-inflammatory, which promotes low grade systemic inflammation and insulin resistance in obese mice. Various T cell subsets either help maintain metabolic homeostasis in healthy states or contribute to obesity-associated metabolic syndromes.

The nonclassical immune surveillance for ERAAP function.

The peptide repertoire presented by MHC class I molecules on the cell surface is essential for the immune surveillance of intracellular pathogens and transformed cells. The generation of this peptide repertoire is critically dependent on the endoplasmic reticulum aminopeptidase associated with antigen processing (ERAAP). Loss of ERAAP function leads to the generation of a profoundly disrupted peptide repertoire including many novel and immunogenic peptides.

Biochemical Analysis of Naturally Processed Antigenic Peptides Presented by MHC Class I Molecules.

Immune surveillance of infected or tumor cells by CD8 T cells requires that MHC class I molecules present a diverse repertoire of peptides on the cell surface. Even a few copies of individual peptides among this mixture are sufficient for recognition by the antigen receptors of appropriate CD8 T cells. Here we describe methods for biochemical analysis of the naturally processed peptides and their precursors in living cells.

Casting a wider net: Immunosurveillance by nonclassical MHC molecules.

Most studies of T lymphocytes focus on recognition of classical major histocompatibility complex (MHC) class I or II molecules presenting oligopeptides, yet there are numerous variations and exceptions of biological significance based on recognition of a wide variety of nonclassical MHC molecules. These include αβ and γδ T cells that recognize different class Ib molecules (CD1, MR-1, HLA-E, G, F, et al.) that are nearly monomorphic within a given species.

A peptide puzzle.

Why does cancer develop in situations where the immune system is perfectly capable of eliminating it?

A peptide-based fluorescent probe images ERAAP activity in cells and in high throughput assays.

ERAAP is an intracellular amino-peptidase that plays a central role in determining the repertoire of peptides displayed by cells by MHC class I molecules, and dysfunctions in ERAAP are linked to a variety of diseases. There is therefore great interest in developing probes that can image ERAAP in cells. In this report we present a fluorescent probe, termed Ep, that can image ERAAP activity in live cells.

Determination of a Key Antigen for Immunological Intervention To Target the Latent Stage of .

, an obligate intracellular protozoan parasite, establishes a chronic infection by forming cysts preferentially in the brain. Up to one third of the human population worldwide is estimated to be chronically infected with this parasite. However, there is currently no drug effective against the cyst form of the parasite.

Antigen Processing in the Endoplasmic Reticulum Is Monitored by Semi-Invariant αβ TCRs Specific for a Conserved Peptide-Qa-1 MHC Class Ib Ligand.

Ag processing in the endoplasmic reticulum (ER) by the ER aminopeptidase associated with Ag processing (ERAAP) is central to presentation of a normal peptide-MHC class I (MHC I) repertoire. Alternations in ERAAP function cause dramatic changes in the MHC I-presented peptides, which elicit potent immune responses. An unusual subset of CD8 T cells monitor normal Ag processing by responding to a highly conserved FL9 peptide that is presented by Qa-1, a nonclassical MHC Ib molecule (QFL) in ERAAP-deficient cells.

Presentation of Cryptic Peptides by MHC Class I Is Enhanced by Inflammatory Stimuli.

Cytolytic T cells eliminate infected or cancer cells by recognizing peptides presented by MHC class I molecules on the cell surface. The antigenic peptides are derived primarily from newly synthesized proteins including those produced by cryptic translation mechanisms. Previous studies have shown that cryptic translation can be initiated by distinct mechanisms at non-AUG codons in addition to conventional translation initiated at the canonical AUG start codon.

Continuous Effector CD8(+) T Cell Production in a Controlled Persistent Infection Is Sustained by a Proliferative Intermediate Population.

Highly functional CD8(+) effector T (Teff) cells can persist in large numbers during controlled persistent infections, as exemplified by rare HIV-infected individuals who control the virus. Here we examined the cellular mechanisms that maintain ongoing T effector responses using a mouse model for persistent Toxoplasma gondii infection. In mice expressing the protective MHC-I molecule, H-2L(d), a dominant T effector response against a single parasite antigen was maintained without a contraction phase, correlating with ongoing presentation of the dominant antigen.

Transnuclear CD8 T cells specific for the immunodominant epitope Gra6 lower acute-phase Toxoplasma gondii burden.

We generated a CD8 T-cell receptor (TCR) transnuclear (TN) mouse specific to the L -restricted immunodominant epitope of GRA6 from Toxoplasma gondii as a source of cells to facilitate further investigation into the CD8 T-cell-mediated response against this pathogen. The TN T cells bound L -Gra6 tetramer and proliferated upon unspecific and peptide-specific stimulation. The TCR beta sequence of the Gra6-specific TN CD8 T cells is identical in its V- and J-region to the TCR-β harboured by a hybridoma line generated in response to Gra6 peptide.

ERAAP Shapes the Peptidome Associated with Classical and Nonclassical MHC Class I Molecules.

The peptide repertoire presented by classical as well as nonclassical MHC class I (MHC I) molecules is altered in the absence of the endoplasmic reticulum aminopeptidase associated with Ag processing (ERAAP). To characterize the extent of these changes, peptides from cells lacking ERAAP were eluted from the cell surface and analyzed by high-throughput mass spectrometry. We found that most peptides found in wild-type (WT) cells were retained in the absence of ERAAP.

Nowhere to hide: unconventional translation yields cryptic peptides for immune surveillance.

Effective immune surveillance by CD8(+) cytotoxic T cells of intracellular microbes and cancer depends on the antigen presentation pathway. This pathway produces an optimal peptide repertoire for presentation by major histocompatibility (MHC) class I molecules (pMHCs I) on the cell surface. We have known for years that the pMHC I repertoire is a reflection of the intracellular protein pool.

Translation from the 5' untranslated region shapes the integrated stress response.

Translated regions distinct from annotated coding sequences have emerged as essential elements of the proteome. This includes upstream open reading frames (uORFs) present in mRNAs controlled by the integrated stress response (ISR) that show "privileged" translation despite inhibited eukaryotic initiation factor 2-guanosine triphosphate-initiator methionyl transfer RNA (eIF2·GTP·Met-tRNA(i )(Met)). We developed tracing translation by T cells to directly measure the translation products of uORFs during the ISR.

Impact of regulated secretion on antiparasitic CD8 T cell responses.

CD8 T cells play a key role in defense against the intracellular parasite Toxoplasma, but why certain CD8 responses are more potent than others is not well understood. Here, we describe a parasite antigen, ROP5, that elicits a CD8 T cell response in genetically susceptible mice. ROP5 is secreted via parasite organelles termed rhoptries that are injected directly into host cells during invasion, whereas the protective, dense-granule antigen GRA6 is constitutively secreted into the parasitophorous vacuole.

Monitoring peptide processing for MHC class I molecules in the endoplasmic reticulum.

Classical MHC class I molecules open a window into the cell by presenting intracellular peptides (pMHC I) on the surface. The peptides are used for immune surveillance by circulating CD8+ T and NK cells to detect and eliminate infected or tumor cells. Not surprisingly, viruses and tumor cells have evolved immune evasion mechanisms to keep the window shades down and the cytotoxic cells oblivious to their presence.

Critical role of endoplasmic reticulum aminopeptidase 1 in determining the length and sequence of peptides bound and presented by HLA-B27.

Objective: HLA-B27 and endoplasmic reticulum aminopeptidase 1 (ERAP1) are the two strongest genetic factors predisposing to ankylosing spondylitis (AS). A key aminopeptidase in class I major histocompatibility complex presentation, ERAP1 potentially contributes to the pathogenesis of AS by altering HLA-B27 peptide presentation. The aim of this study was to analyze the effects of ERAP1 on the HLA-B27 peptide repertoire and peptide presentation to cytotoxic T lymphocytes (CTLs).

ERAAP and tapasin independently edit the amino and carboxyl termini of MHC class I peptides.

Effective CD8(+) T cell responses depend on presentation of a stable peptide repertoire by MHC class I (MHC I) molecules on the cell surface. The overall quality of peptide-MHC I complexes (pMHC I) is determined by poorly understood mechanisms that generate and load peptides with appropriate consensus motifs onto MHC I. In this article, we show that both tapasin (Tpn), a key component of the peptide loading complex, and the endoplasmic reticulum aminopeptidase associated with Ag processing (ERAAP) are quintessential editors of distinct structural features of the peptide repertoire.

Location of the CD8 T cell epitope within the antigenic precursor determines immunogenicity and protection against the Toxoplasma gondii parasite.

CD8 T cells protect the host from disease caused by intracellular pathogens, such as the Toxoplasma gondii (T. gondii) protozoan parasite. Despite the complexity of the T.