MHC Class Ib Molecule Research Articles

HELIOS-expressing human CD8 T cells exhibit limited effector functions.

The transcription factor HELIOS is primarily known for its expression in CD4 regulatory T cells, both in humans and mice. In mice, HELIOS is found in exhausted CD8 T cells. However, information on human HELIOS+ CD8 T cells is limited and conflicting. In this study, we characterized by flow cytometry and transcriptomic analyses human HELIOS+ CD8 T cells. These T cells primarily consist of memory cells and constitute approximately 21% of blood CD8 T cells. In comparison with memory HELIOS- T-BEThigh CD8 T cells that displayed robust effector functions, the memory HELIOS+ T-BEThigh CD8 T cells produce lower amounts of IFN-γ and TNF-α and have a lower cytotoxic potential. We wondered if these cells participate in the immune response against viral antigens, but did not find HELIOS+ cells among CD8 T cells recognizing CMV peptides presented by HLA-A2 and HLA-B7. However, we found HELIOS+ CD8 T cells that recognize a CMV peptide presented by MHC class Ib molecule HLA-E. Additionally, a portion of HELIOS+ CD8 T cells is characterized by the expression of CD161, often used as a surface marker for identifying TC17 cells. These CD8 T cells express TH17/TC17-related genes encoding RORgt, RORa, PLZF, and CCL20. Our findings emphasize that HELIOS is expressed across various CD8 T cell populations, highlighting its significance beyond its role as a transcription factor for Treg or exhausted murine CD8 T cells. The significance of the connection between HELIOS and HLA-E restriction is yet to be understood.

Alpha-synuclein peptides presented on chimeric MHC class Ib molecules prevent loss of substantia nigra neurons in an animal model for Parkinson’s disease

Abstract Aim An accumulating body of evidence suggests the involvement of alpha-synuclein (aSyn) specific autoreactive T cells in Parkinson’s disease (PD). Here, we investigate whether novel antigen-specific tolerance-inducing biomolecules, that present peptide antigens on MHC class Ib-related molecules, can inhibit neurodegeneration and prevent PD in vivo. Methods The alpha3 domain of the human MHC class Ib molecule HLA-G inhibits T cells via the human ILT-2 or the murine PIRB receptor. We fused this HLA-G alpha3 domain to MHC class I alpha1-alpha2 antigen presenting domains, antigenic peptides and beta2-microglobulin. These single-chain AutoImmunity Modifying Biologicals (AIM Bios) induce antigen-specific tolerogenic CD8+ Treg cells in human cells in vitro and in mice in vivo. We used this platform to prevent autoimmune disease symptoms in mouse models for autoimmune diseases, including an aSynA53T-AAV driven model for PD. Results Single-chain model AIM Bios with MHC-derived antigen-presenting domains and antigenic peptides polarize cognate CD8+ T cells towards a CD8+CD122+ IL-10 secreting Treg phenotype. Such antigen-specific Treg can also be induced in mice in vivo. Disease-associated aSyn CD8+ epitopes were identified in aSynA53T-AAV PD mice. Corresponding AIM Bios prevented mobility impairments. Post mortem histopathological assessment confirmed the induction a favorable in-situ immune cell composition and the rescue of substantia nigra neurons. The translational potential of this approach deserves further exploration. Supported by grants from the IZKF Wuerzburg A421 and by Aeterna Zentaris Inc.

Human Leucocyte Antigen G and Murine Qa-2 Are Critical for Myeloid Derived Suppressor Cell Expansion and Activation and for Successful Pregnancy Outcome.

During pregnancy, maternal immune system has to balance tightly between protection against pathogens and tolerance towards a semi-allogeneic organism. Dysfunction of this immune adaptation can lead to severe complications such as pregnancy loss, preeclampsia or fetal growth restriction. In the present study we analyzed the impact of the murine MHC class Ib molecule Qa-2 on pregnancy outcome in vivo. We demonstrate that lack of Qa-2 led to intrauterine growth restriction and increased abortion rates especially in late pregnancy accompanied by a disturbed trophoblast invasion and altered spiral artery remodeling as well as protein aggregation in trophoblast cells indicating a preeclampsia-like phenotype. Furthermore, lack of Qa-2 caused imbalanced immunological adaptation to pregnancy with altered immune cell and especially T-cell homeostasis, reduced Treg numbers and decreased accumulation and functional activation of myeloid-derived suppressor cells. Lastly, we show that application of sHLA-G reduced abortion rates in Qa-2 deficient mice by inducing MDSC. Our results highlight the importance of an interaction between HLA-G and MDSC for pregnancy success and the therapeutic potential of HLA-G for treatment of immunological pregnancy complications.

Immunodominant, Qa-1-restricted CD8 T cell response elicited against a non-canonical translation product in influenza A virus

Abstract The extent to which non-canonical translation products drive antiviral T cell responses is incompletely understood. We explored this question using an immunopeptidomic approach in an influenza virus model. C57Bl/6 mouse-derived cells were infected with influenza virus A/Puerto Rico/8/1934 (PR8), and MHC-bound peptides were eluted and analyzed by tandem mass spectrometry. Mass spectra were searched against a database of all viral gene segments translated in all possible reading frames, irrespective of the presence of start codons. We identified a 9-mer peptide, here termed M-SL9, that maps to an alternative reading frame of the sequence encoding matrix protein 1 (M1). To validate M-SL9 as a T cell epitope, we infected C57Bl/6 mice with PR8, collected tissues, and measured T cell reactivation by synthetic M-SL9 peptide. Remarkably, 10% of all CD8 T cells in the lung were specifically reactivated by M-SL9 peptide, and the vast majority of these were polyfunctional, producing two or more Th1 cytokines. An analysis of M-SL9 processing and presentation revealed that M-SL9 is restricted to the non-classical MHC class Ib molecule, Qa-1, and that presentation is dependent on the second 5′-proximal AUG codon within the M1-coding sequence, suggesting that its translation results from leaky ribosomal scanning. These data contribute to a growing body of work showing the importance of non-canonical MHC presentation in protective immune responses.

Peptide Binding to HLA-E Molecules in Humans, Nonhuman Primates, and Mice Reveals Unique Binding Peptides but Remarkably Conserved Anchor Residues.

Ag presentation via the nonclassical MHC class Ib molecule HLA-E, with nearly complete identity between the two alleles expressed in humans, HLA-E*01:01 and HLA-E*01:03, can lead to the activation of unconventional T cells in humans. Despite this virtual genetic monomorphism, differences in peptide repertoires binding to the two allelic variants have been reported. To further dissect and compare peptide binding to HLA-E*01:01 and HLA-E*01:03, we used an UV-mediated peptide exchange binding assay and an HPLC-based competition binding assay. In addition, we investigated binding of these same peptides to Mamu-E, the nonhuman primate homologue of human HLA-E, and to the HLA-E-like molecule Qa-1b in mice. We next exploited the differences and homologies in the peptide binding pockets of these four molecules to identify allele specific as well as common features of peptide binding motifs across species. Our results reveal differences in peptide binding preferences and intensities for each human HLA-E variant compared with Mamu-E and Qa-1b Using extended peptide libraries, we identified and refined the peptide binding motifs for each of the four molecules and found that they share main anchor positions, evidenced by conserved amino acid preferences across the four HLA-E molecules studied. In addition, we also identified differences in peptide binding motifs, which could explain the observed variations in peptide binding preferences and affinities for each of the four HLA-E-like molecules. Our results could help with guiding the selection of candidate pathogen-derived peptides with the capacity to target HLA-E-restricted T cells that could be mobilized in vaccination and immunotherapeutic strategies.

Covering All the Bases: Complementary MR1 Antigen Presentation Pathways Sample Diverse Antigens and Intracellular Compartments.

The ubiquitously expressed, monomorphic MHC class Ib molecule MHC class I-related protein 1 (MR1) presents microbial metabolites to mucosal-associated invariant T (MAIT) cells. However, recent work demonstrates that both the ligands bound by MR1 and the T cells restricted by it are more diverse than originally thought. It is becoming increasingly clear that MR1 is capable of presenting a remarkable variety of both microbial and non-microbial small molecule antigens to a diverse group of MR1-restricted T cells (MR1Ts) and that the antigen presentation pathway differs between exogenously delivered antigen and intracellular microbial infection. These distinct antigen presentation pathways suggest that MR1 shares features of both MHC class I and MHC class II antigen presentation, enabling it to sample diverse intracellular compartments and capture antigen of both intracellular and extracellular origin. Here, we review recent developments and new insights into the cellular mechanisms of MR1-dependent antigen presentation with a focus on microbial MR1T cell antigens.

Constitutively expressed MHC class Ib molecules regulate macrophage M2b polarization and sepsis severity in irradiated mice.

Macrophages can change their physiology in response to microenvironmental signals. This differentiation into classically activated M1 or alternatively activated M2 macrophages is known as polarization. In this study, we isolated bone marrow-derived macrophages from β2m-deficient (deficient in both MHC class Ia and Ib) and Kb Db -deficient (deficient only in MHC class Ia) mice and found that β2m-deficient macrophages showed a significantly lower M2b polarization efficiency. In addition, the absence of constitutive MHC class Ib expression decreased the stability of the Notch-1 intracellular domain. Finally, we found that β2m-deficient mice exposed to irradiation showed reduced bacterial translocation and sepsis severity. Overall, our study demonstrates that MHC class Ib molecules are essential for M2b macrophage polarization and suggests that MHC class Ib molecules play an important role during infection-induced innate immunity.

Molecular mechanisms of lineage decisions in metabolite-specific T cells.

Mucosal-associated invariant T cells (MAIT cells) recognize the microbial metabolite 5-(2-oxopropylideneamino)-6-D-ribitylaminouracil (5-OP-RU) presented by the MHC class Ib molecule, MR1. MAIT cells acquire effector functions during thymic development, but the mechanisms involved are unclear. Here we used single-cell RNA-sequencing to characterize the developmental path of 5-OP-RU-specific thymocytes. In addition to the known MAIT1 and MAIT17 effector subsets selected on bone-marrow-derived hematopoietic cells, we identified 5-OP-RU-specific thymocytes that were selected on thymic epithelial cells and differentiated into CD44- naive T cells. MAIT cell positive selection required signaling through the adapter, SAP, that controlled the expression of the transcription factor, ZBTB16. Pseudotemporal ordering of single cells revealed transcriptional trajectories of 5-OP-RU-specific thymocytes selected on either thymic epithelial cells or hematopoietic cells. The resulting model illustrates T cell lineage decisions.

Qa-1-Restricted CD8+ T Cells Can Compensate for the Absence of Conventional T Cells during Viral Infection

SUMMARYThe role of non-classical T cells during viral infection remains poorly understood. Using the well-established murine model of CMV infection (MCMV) and mice deficient in MHC class Ia molecules, we found that non-classical CD8+ T cells robustly expand after MCMV challenge, become highly activated effectors, and are capable of forming durable memory. Interestingly, although these cells are restricted by MHC class Ib molecules, they respond similarly to conventional T cells. Remarkably, when acting as the sole component of the adaptive immune response, non-classical CD8+ T cells are sufficient to protect against MCMV-induced lethality. We also demonstrate that the MHC class Ib molecule Qa-1 (encoded by H2-T23) restricts a large, and critical, portion of this population. These findings reveal a potential adaptation of the host immune response to compensate for viral evasion of classical T cell immunity.

T Cells Engaging the Conserved MHC Class Ib Molecule Qa-1b with TAP-Independent Peptides Are Semi-Invariant Lymphocytes.

The HLA-E homolog in the mouse (Qa-1b) is a conserved MHC class Ib molecule presenting monomorphic peptides to germline-encoded natural killer receptor CD94/NKG2A. Previously, we demonstrated the replacement of this canonical peptide by a diverse peptidome upon deficiency of the TAP peptide transporter. Analysis of this Qa-1b-restricted T cell repertoire against these non-mutated neoantigens revealed characteristics of conventional hypervariable CD8+ T cells, but also of invariant T cell receptor (TCR)αβ T cells. A shared TCR Vα chain was used by this subset in combination with a variety of Vβ chains. The TCRs target peptide ligands that are conserved between mouse and man, like the identified peptide derived from the transcriptional cofactor Med15. The thymus selection was studied in a TCR-transgenic mouse and emerging naïve CD8+ T cells displayed a slightly activated phenotype, as witnessed by higher CD122 and Ly6C expression. Moreover, the Qa-1b protein was dispensable for thymus selection. Importantly, no self-reactivity was observed as reported for other MHC class Ib-restricted subsets. Naïve Qa-1b restricted T cells expanded, contracted, and formed memory cells in vivo upon peptide vaccination in a similar manner as conventional CD8+ T cells. Based on these data, the Qa-1b restricted T cell subset might be positioned closest to conventional CD8+ T cells of all MHC class Ib populations.

The Role of MHC-E in T Cell Immunity Is Conserved among Humans, Rhesus Macaques, and Cynomolgus Macaques.

MHC-E is a highly conserved nonclassical MHC class Ib molecule that predominantly binds and presents MHC class Ia leader sequence-derived peptides for NK cell regulation. However, MHC-E also binds pathogen-derived peptide Ags for presentation to CD8+ T cells. Given this role in adaptive immunity and its highly monomorphic nature in the human population, HLA-E is an attractive target for novel vaccine and immunotherapeutic modalities. Development of HLA-E-targeted therapies will require a physiologically relevant animal model that recapitulates HLA-E-restricted T cell biology. In this study, we investigated MHC-E immunobiology in two common nonhuman primate species, Indian-origin rhesus macaques (RM) and Mauritian-origin cynomolgus macaques (MCM). Compared to humans and MCM, RM expressed a greater number of MHC-E alleles at both the population and individual level. Despite this difference, human, RM, and MCM MHC-E molecules were expressed at similar levels across immune cell subsets, equivalently upregulated by viral pathogens, and bound and presented identical peptides to CD8+ T cells. Indeed, SIV-specific, Mamu-E-restricted CD8+ T cells from RM recognized antigenic peptides presented by all MHC-E molecules tested, including cross-species recognition of human and MCM SIV-infected CD4+ T cells. Thus, MHC-E is functionally conserved among humans, RM, and MCM, and both RM and MCM represent physiologically relevant animal models of HLA-E-restricted T cell immunobiology.

MAIT cells: an historical and evolutionary perspective.

In humans, MAIT cells represent the most abundant T-cell subset reacting against bacteria. MAIT cells belong to the evolutionarily conserved family of "preset" T cells that includes also NKT cells. Both subsets are selected by double positive thymocytes leading to common features such as PLZF expression. Preset T cells correspond to subsets prepositioned in specific tissue locations with preprogrammed versatile effector functions such as antimicrobial functions and possibly also metabolic control and tissue repair activity. Herein, we recall how several groups studying human samples discovered MAIT cells as T cells expressing either a restricted T-cell receptors (TCR) repertoire or homogeneous and singular phenotypic and functional characteristics. We then highlight the main evolutionary features of this subset and its restricting element, MR1 (MHC-related protein (1) with a striking coevolution of TRAV1 and MR1. We introduce another evolutionarily conserved invariant TCRalpha chain coevolving with another MHC class Ib molecule, called MHX, sharing phylogenetic features with MR1. We finally discuss the relationship between MAIT cells and other subsets reacting to microbial antigens or to compounds presented by MR1 in light of confounding experimental issues.

A conserved energetic footprint underpins recognition of human leukocyte antigen-E by two distinct αβ T cell receptors

αβ T cell receptors (TCRs) interact with peptides bound to the polymorphic major histocompatibility complex class Ia (MHC-Ia) and class II (MHC-II) molecules as well as the essentially monomorphic MHC class Ib (MHC-Ib) molecules. Although there is a large amount of information on how TCRs engage with MHC-Ia and MHC-II, our understanding of TCR/MHC-Ib interactions is very limited. Infection with cytomegalovirus (CMV) can elicit a CD8+ T cell response restricted by the human MHC-Ib molecule human leukocyte antigen (HLA)-E and specific for an epitope from UL40 (VMAPRTLIL), which is characterized by biased TRBV14 gene usage. Here we describe an HLA-E-restricted CD8+ T cell able to recognize an allotypic variant of the UL40 peptide with a modification at position 8 (P8) of the peptide (VMAPRTLVL) that uses the TRBV9 gene segment. We report the structures of a TRBV9+ TCR in complex with the HLA-E molecule presenting the two peptides. Our data revealed that the TRBV9+ TCR adopts a different docking mode and molecular footprint atop HLA-E when compared with the TRBV14+ TCR-HLA-E ternary complex. Additionally, despite their differing V gene segment usage and different docking mechanisms, mutational analyses showed that the TCRs shared a conserved energetic footprint on the HLA-E molecule, focused around the peptide-binding groove. Hence, we provide new insights into how monomorphic MHC molecules interact with T cells.

Intraepithelial CD94+ tumor-infiltrating lymphocytes in a context of HLA-E overexpression as a new immune checkpoint to predict prognosis in colorectal carcinomas.

e14592 Background: A better understanding of the immune-modulating interactions between tumor cells and immune cells underlying the balance between immune control and immune resistance in colorectal cancer (CRC) is crucial for the design of immunotherapies. We have previously demonstrated that overexpression of the human MHC class Ib molecule - HLA-E/β2 microglobulin - by tumor cells in CRC was associated with an unfavorable prognosis, suggesting its involvement in immune escape. However, the specific receptor of HLA-E/β2m - CD94/NKG2A, inhibitory or CD94/NKG2C, activating - expressed by tumor-infiltrating lymphocytes (TIL), as well as the influence of the microsatellite status in HLA-E/β2m overexpression, remain unknown. Methods: We investigated in the primary tumor of 245 CRC patients 1) the association of HLA-E/β2m overexpression and the density of CD94+ intraepithelial TIL (IEL-TIL) with the microsatellite status, 2) the nature of CD94+ TIL and the receptor expressed - CD94/NKG2A or CD94/NKG2C - and 3) the prognostic influence of CD94+ IEL-TIL. Results: HLA-E/β2m was preferentially overexpressed in MSI compared with MSS CRC (44,6 % vs 18,4 % respectively, p = 0.0001), and significantly associated with a high density of CD94+ IEL-TIL in MSI (0,9% in HLA-E/β2m+ vs 0,2% in HLA-E/β2m– CRC, p = 0,001), and in MSS CRC (0,38% vs 0,15%, p < 0,0001). These CD94+ TIL mostly corresponded to CD8+ αβ T cells preferentially expressing the inhibitory NKG2A chain. Finally, a high density of CD94+ IEL-TIL was independently associated with a worse OS (p = 0.03). Conclusions: These results strongly suggest that HLA-E/β2m - CD94/NKG2A interactions, preferentially up-regulated in MSI CRC, represent a promising inhibitory immune checkpoint. From a clinical point of view, this inhibitory immune checkpoint could be blocked by the new anti-NKG2A monoclonal antibody.

Invariant NKT Cell Activation Is Potentiated by Homotypic trans-Ly108 Interactions.

Invariant NKT (iNKT) cells are innate lymphocytes that respond to glycolipids presented by the MHC class Ib molecule CD1d and are rapidly activated to produce large quantities of cytokines and chemokines. iNKT cell development uniquely depends on interactions between double-positive thymocytes that provide key homotypic interactions between signaling lymphocyte activation molecule (SLAM) family members. However, the role of SLAM receptors in the differentiation of iNKT cell effector subsets and activation has not been explored. In this article, we show that C57BL/6 mice containing the New Zealand Black Slam locus have profound alterations in Ly108, CD150, and Ly9 expression that is associated with iNKT cell hyporesponsiveness. This loss of function was only apparent when dendritic cells and iNKT cells had a loss of SLAM receptor expression. Using small interfering RNA knockdowns and peptide-blocking strategies, we demonstrated that trans-Ly108 interactions between dendritic cells and iNKT cells are critical for robust activation. LY108 costimulation similarly increased human iNKT cell activation. Thus, in addition to its established role in iNKT cell ontogeny, Ly108 regulates iNKT cell function in mice and humans.

Human CD8+ Treg after Allogeneic Stem-Cell Transplantation

Murine CD8+ regulatory T cells (Treg) are characterized by expression of the cell surface triad CD44, CD122 and Ly49 and require the transcription factor Helios for stable regulatory function. This regulatory CD8+ T cell subset recognizes target cells through the recognition of the Qa-1-molecule (HLA-E in man), resulting in perforin-dependent elimination of target cells. Qa-1 is a MHC class Ib molecule that presents a limited repertoire of peptides that generally serve as an indicator of cellular activation and stress. Until now, CD4+ follicular T helper cells (TFH) and CD8+ effector T cells have been identified as direct target cells of CD8+ Treg.The therapeutic success of allogeneic stem-cell transplantation (allo-SCT) as an immunotherapeutic approach to treat hematological diseases is often limited by Graft-versus-Host Disease (GvHD). Major factors for the development of GvHD are allo-reactive CD4+ TFH and CD8+ effector T cells. CD4+ regulatory T cells (Treg) have been shown to be beneficial in the prevention and/or treatment of GvHD while sparing the Graft-versus-Leukemia effect. The contribution of regulatory CD8+ T cell-mediated immune responses in GvHD has not been studied so far. However, targeting CD4+ TFH and CD8+ effector T cells, CD8+ Treg are feasible candidates as additional important players in immune regulation during GvHD development.Here we have analyzed the development of CD8+ Treg after allogeneic stem-cell transplantation in humans. Using the knowledge derived from murine studies, the killer cell immunoglobulin-like receptor (KIR), the functional homologue of the murine Ly49 receptor, was used as a surface marker on CD8+ T cells to determine the human regulatory CD8+ T cell subset. In humans, CD8+ Treg also express CD44, CD122 and the transcription factor Helios similar to murine CD8+ Treg. In vitro proliferation studies with IL-2, IL-12, IL-15 and IL-18 showed dose dependent proliferation kinetics of KIR+CD8+ Treg vs KIR-CD8+ T cells. Of note, after cytokine stimulation and cell proliferation for up to 12 days, KIR+CD8+ T cells remained phenotypically stable while KIR-CD8+ T cells did not up-regulate KIR expression. Similar results were obtained in analyses of Helios expression in CD8+ Treg during cytokine stimulation. In patients after allogeneic stem-cell transplantation, CD8+ Treg development occurs early together with reconstitution of other immune cell subsets. Subsequently, CD8+ Treg reconstitution reaches its peak around day +90 after allo-SCT. Compared with samples from healthy donors, CD8+ Treg after allo-SCT show similar surface phenotype characteristics, while Helios expression is up-regulated after allo-SCT.In summary, we have further characterized the KIR+CD8+ Treg population with distinct phenotypical and functional responses to cytokine stimulation when compared with KIR-CD8+ T cells. This KIR+CD8+ regulatory T cell subset recovers early in patients after allogeneic stem-cell transplantation with comparable characteristics to CD8+ Treg from healthy donors, with the exception of an up-regulated expression of Helios in CD8+ Treg after allo-SCT. The rapid generation of CD8+ Treg during regeneration of the immune system in these patients implicates an important role for this cell subset during immune reconstitution and may control development of GvHD. Further functional analyses of KIR+CD8+ T cells in patients after allo-SCT may be helpful in understanding the involvement of CD8+ Treg in the pathogenesis of acute and chronic GvHD. Following these results, specific activation/expansion of CD8+ Treg may then lead to additional cellular immune-modulatory options for the treatment and prevention of GvHD. DisclosuresNo relevant conflicts of interest to declare.

Nonclassical MHC Ib-restricted CD8+ T Cells Recognize Mycobacterium tuberculosis-Derived Protein Antigens and Contribute to Protection Against Infection.

MHC Ib-restricted CD8+ T cells have been implicated in host defense against Mycobacterium tuberculosis (Mtb) infection. However, the relative contribution of various MHC Ib-restricted T cell populations to anti-mycobacterial immunity remains elusive. In this study, we used mice that lack MHC Ia (Kb-/-Db-/-), MHC Ia/H2-M3 (Kb-/-Db-/-M3-/-), or β2m (β2m-/-) to study the role of M3-restricted and other MHC Ib-restricted T cells in immunity against Mtb. Unlike their dominant role in Listeria infection, we found that M3-restricted CD8+ T cells only represented a small proportion of the CD8+ T cells responding to Mtb infection. Non-M3, MHC Ib-restricted CD8+ T cells expanded preferentially in the lungs of Mtb-infected Kb-/-Db-/-M3-/- mice, exhibited polyfunctional capacities and conferred protection against Mtb. These MHC Ib-restricted CD8+ T cells recognized several Mtb-derived protein antigens at a higher frequency than MHC Ia-restricted CD8+ T cells. The presentation of Mtb antigens to MHC Ib-restricted CD8+ T cells was mostly β2m-dependent but TAP-independent. Interestingly, a large proportion of Mtb-specific MHC Ib-restricted CD8+ T cells in Kb-/-Db-/-M3-/- mice were Qa-2-restricted while no considerable numbers of MR1 or CD1-restricted Mtb-specific CD8+ T cells were detected. Our findings indicate that nonclassical CD8+ T cells other than the known M3, CD1, and MR1-restricted CD8+ T cells contribute to host immune responses against Mtb infection. Targeting these MHC Ib-restricted CD8+ T cells would facilitate the design of better Mtb vaccines with broader coverage across MHC haplotypes due to the limited polymorphism of MHC class Ib molecules.

Two different nonclassical MHC class I-restricted invariant T cell lineages with non-overlapping antiviral and anti-mycobacterial immune functions in the amphibian Xenopus

Abstract Unconventional T cells, including disparate populations of MHC class Ib-reactive innate T (iT) cells are emerging as key factors in the immune system partly due to their public antigen specificities and rapid effector responses. The biological relevance and evolutionary conservation of iT cells have, over the past few years, been strengthened by studies in the amphibian Xenopus, which have revealed an overrepresentation of several invariant TCRs in tadpoles and identified a prominent subset of iT cells (invariant Vα6 [iVα6]) restricted by the nonclassical MHC class Ib molecule XNC10. Recently, we showed that similar to CD1d restricted iNKT cells in humans and mice Xenopus iVα6 T cells are critical for early antiviral immunity. Here, using RNAi loss-of-function by transgenesis targeting another Xenopus nonclassical gene, XNC4, we have identified a different XNC4-dependent iT cell population expressing one of the 6 previously identified overrepresented TCRα rearrangements (TRAV45 joined to TRAJ1.14). We show that this invariant Vα45 [iVα45] T cell population is critical for antibacterial immunity against Mycobacterium marinum. These data suggest that functionally distinct populations of MHC class Ib-reactive iT cell populations play a prominent role in amphibian immune defense and as such may represent a more primordial immune cell type that previously thought.

Broadly targeted CD8 + T cell responses restricted by major histocompatibility complex E

Major histocompatibility complex E (MHC-E) is a highly conserved, ubiquitously expressed, nonclassical MHC class Ib molecule with limited polymorphism that is primarily involved in the regulation of natural killer (NK) cells. We found that vaccinating rhesus macaques with rhesus cytomegalovirus vectors in which genes Rh157.5 and Rh157.4 are deleted results in MHC-E-restricted presentation of highly varied peptide epitopes to CD8αβ(+) T cells, at ~4 distinct epitopes per 100 amino acids in all tested antigens. Computational structural analysis revealed that MHC-E provides heterogeneous chemical environments for diverse side-chain interactions within a stable, open binding groove. Because MHC-E is up-regulated to evade NK cell activity in cells infected with HIV, simian immunodeficiency virus, and other persistent viruses, MHC-E-restricted CD8(+) T cell responses have the potential to exploit pathogen immune-evasion adaptations, a capability that might endow these unconventional responses with superior efficacy.

Population genetic structure for gene HLA-G in NorthWest Russia

HLA-G is a nonclassical MHC class Ib molecule predominantly expressed in cytotrophoblasts and also under pathological conditions in chronically inflamed and malignant tissues. Polymorphisms of the HLA-G gene, some of which are functionally important, may potentially affect both the coding and noncoding regions of this gene. Using the PCR method we studied polymorphism of the HLA-G gene (alleles G*0101–0107,–725C/G, and 3741del/ins14) in 118 individuals aged from 20 to 40 years and living in the NorthWest Region of Russia (St. Petersburg). In order to determine major alleles of the HLA-G gene, the system of primers for multiplex allele-specific PCR was elaborated. The HLA-G allele distribution in residents of the NorthWest Region of Russia was determined. The minor allele frequencies varied in wide ranges, from 0% to 39%. Cluster analysis was carried out and the genetic distances between the Spanish, Chinese, Japanese, Danish, Indian, African Shona, Brazilian, Polish, and German populations, as well as the population of the NorthWest Region of Russia, were calculated. The similarity of the distribution of frequencies of alleles G*0101–0107 and polymorphism 3741del/ins14 in the Danish, German, and NorthWest Region’s populations was shown.