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[CD8.sup.+] T cells destroy insulin-producing pancreatic [beta] cells in type 1 diabetes through HLA class I- restricted presentation of self-antigens. Combinatorial peptide library screening was used to produce a preferred peptide recognition landscape for a patient-derived T cell receptor (TCR) that recognized the preproinsulin-derived (PPI-derived) peptide sequence LWMRLLPLL in the context of disease risk allele HLA A*24:02. Data were used to generate a strong superagonist peptide, enabling production of an autoimmune HLA A*24:02-peptide-TCR structure by crystal seeding. TCR binding to the PPI epitope was strongly focused on peptide residues Arg4 and Leu5, with more flexibility at other positions, allowing the TCR to strongly engage many peptides derived from pathogenic bacteria. We confirmed an epitope from Klebsiella that was recognized by PPI-reactive T cells from 3 of 3 HLA A*24:02+ patients. Remarkably, the same epitope selected T cells from 7 of 8 HLA A*24* healthy donors that cross-reacted with PPI, leading to recognition and killing of HLA A*24:02+ cells expressing PPI. These data provide a mechanism by which molecular mimicry between pathogen and self-antigens could have resulted in the breaking of self-tolerance to initiate disease., Introduction Multiple lines of evidence show that type 1 diabetes (T1D) develops due to [CD8.sup.+] T cell-mediated destruction of insulin-producing pancreatic [beta] cells. Human leukocyte antigen class I (HLA-I), the [...]

We investigated the interplay between genetics and oral peanut protein exposure in the determination of the immunological response to peanut using the targeted intervention in the LEAP clinical trial. We identified an association between peanut-specific IgG4 and HLA-DQA1*01:02 that was only observed in the presence of sustained oral peanut protein exposure. The association between IgG4 and HLA-DQA1*01:02 was driven by IgG4 specific for the Ara h 2 component. Once peanut consumption ceased, the association between IgG4-specific Ara h 2 and HLA-DQA1*01:02 was attenuated. The association was validated by observing expanded IgG4-specific epitopes in people who carried HLA-DQA1*01:02. Notably, we confirmed the previously reported associations with HLA-DQA1*01:02 and peanut allergy risk in the absence of oral peanut protein exposure. Interaction between HLA and presence or absence of exposure to peanut in an allergen- and epitope-specific manner implicates a mechanism of antigen recognition that is fundamental to driving immune responses related to allergy risk or protection., Introduction The interplay between an individual's genetics and exposure to particular environmental or therapeutic modulators influences mechanisms of disease, prognosis, and treatment. Clinical trials of food allergy tolerance, in which [...]

The rising incidence of food allergy in children underscores the importance of environmental exposures; however, genetic factors play a major role. How the environment and genetics interact to cause food allergy remains unclear. The landmark Learning Early About Peanut Allergy (LEAP) clinical trial established that early peanut introduction protects high-risk infants, consistent with the tolerizing effects of gut exposure. In this issue of the JCI, Kanchan et al. leveraged the LEAP trial data to examine molecular genetic mechanisms of early sensitization. A previously identified HLA risk allele for peanut allergy (DQA1*01:02) was associated with peanut-specific IgG4 levels in consumers. Notably, IgG4 antibodies likely provide protection by reducing the binding of allergen to IgE. The association of the same allele with peanut allergy in avoiders while potentially conferring protection in consumers reinforces the need to integrate genetic information toward a personalized therapeutic strategy for the best outcome in addressing food allergies., Contextual associations between HLA alleles and peanut allergy The genetic factors that predispose an individual to atopy and food allergy including peanut have been evaluated through genome-wide association studies (GWAS) [...]

[CD8.sup.+] T cell responses restricted by MHC-E, a nonclassical MHC molecule, have been associated with protection in an SIV/rhesus macaque model. The biological relevance of HLA-E-restricted [CD8.sup.+] T cell responses in HIV infection, however, remains unknown. In this study, [CD8.sup.+] T cells responding to HIV-1 Gag peptides presented by HLA-E were analyzed. Using in vitro assays, we observed HLA-E-restricted T cell responses to what we believe to be a newly identified subdominant Gag-KL9 as well as a well-described immunodominant Gag-KF11 epitope in T cell lines derived from chronically HIV-infected patients and also primed from healthy donors. Blocking of the HLA-E/KF11 binding by the B7 signal peptide resulted in decreased [CD8.sup.+] T cell responses. KF11 presented via HLA-E in HIV-infected cells was recognized by antigen-specific [CD8.sup.+] T cells. Importantly, bulk [CD8.sup.+] T cells obtained from HIV-infected individuals recognized infected cells via HLA-E presentation. Ex vivo analyses at the epitope level showed a higher responder frequency of HLA-E-restricted responses to KF11 compared with KL9. Taken together, our findings of HLA-E-restricted HIV-specific immune responses offer intriguing and possibly paradigm-shifting insights into factors that contribute to the immunodominance of [CD8.sup.+] T cell responses in HIV infection., Introduction There is compelling evidence that effector [CD8.sup.+] cytotoxic T lymphocytes (CTLs) play a pivotal role in the control of HIV infection (1-3). The paradigm for CTL recognition is via [...]

During embryo implantation and initiation of pregnancy, uterineNK(uNK) cells engage invasive fetal trophoblasts to remodel vessels that conduct blood to the placenta. This partnership, involving uNK cell receptors that recognize HLA-C ligands on trophoblasts, varies the course of human pregnancy because the genes for both receptors and ligands are extraordinarily diverse. Several pregnancy disorders are attributed to insufficient trophoblast invasion and the limitation it imposes on human reproduction. Previously, a particular combination of fetal HLA-C and maternal inhibitory uNK cell receptor was associated with predisposition for preeclampsia. In this issue of the JCI, Hiby and colleagues extend this correlation to recurrent miscarriage and fetal growth restriction, revealing the common mechanism underlying these common pregnancy syndromes. Equally important, they show that mothers with an activating receptor of similar specificity to the inhibitory receptor are less likely to suffer disordered pregnancy., Although glittering prizes for fundamental immunology emerged from the study of lymphocyte responses to genetic polymorphisms within species (1-5), pregnancy is the only situation in which lymphocytes naturally confront another [...]

When used as therapy for hematopoietic malignancies, allogeneic BM transplantation (BMT) relies on the graft-versus-leukemia (GVL) effect to eradicate residual tumor cells through immunologic mechanisms. However, graft-versus-host disease (GVHD), which is initiated by alloreactive donor T cells that recognize mismatched major and/or minor histocompatibility antigens and cause severe damage to hematopoietic and epithelial tissues, is a potentially lethal complication of allogeneic BMT. To enhance the therapeutic potential of BMT, we sought to find therapeutic targets that could inhibit GVHD while preserving GVL and immune responses to infectious agents. We show here that T cell responses triggered in mice by either Listeria monocytogenes or administration of antigen and adjuvant were relatively well preserved in the absence of PKC isoform [theta] (PKC[theta]), a key regulator of TCR signaling. In contrast, PKC[theta] was required for alloreactivity and GVHD induction. Furthermore, absence of PKC[theta] raised the threshold for T cell activation, which selectively affected allo-responses. Most importantly, PKC[theta]-deficient T cells retained the ability to respond to virus infection and to induce GVL effect after BMT. These findings suggest PKC[theta] is a potentially unique therapeutic target required for GVHD induction but not for GVL or protective responses to infectious agents., Introduction The primary signal for T cell activation is delivered by engagement of the TCR with MHC/peptide complexes on APCs. In addition, a second signal is provided by costimulatory molecules [...]

Genetic studies suggest a role for killer cell immunoglobulin-like receptor/HLA (KIR/HLA) compound genotypes in the outcome of viral infections, but functional data to explain these epidemiological observations have not been reported. Using an in vitro model of infection with influenza A virus (IAV), we attribute functional differences in human NK cell activity to distinct KIR/HLA genotypes. Multicolor flow cytometry revealed that the HLA-C--inhibited NK cell subset in HLA-C1 homozygous subjects was larger and responded more rapidly in IFN-[gamma] secretion and CD107a degranulation assays than its counterpart in HLA-C2 homozygous subjects. The differential IFN-[gamma] response was also observed at the level of bulk NK cells and was independent of KIR3DL1/HLA-Bw4 interactions. Moreover, the differential response was not caused by differences in NK cell maturation status and phenotype, nor by differences in the type I IFN response of IAV-infected accessory cells between HLA-C1 and HLA-C2 homozygous subjects. These results provide functional evidence for differential NK cell responsiveness depending on KIR/HLA genotype and may provide useful insights into differential innate immune responsiveness to viral infections such as IAV., Introduction As part of the innate immune system, NK cells present a first line of defense against viral infections and tumors (1). NK cell effector functions, such as cytotoxicity and [...]

Infectious mononucleosis (IM) is an immunopathological disease caused by EBV that occurs in young adultsand is a risk factor for Hodgkin lymphoma (HL). An association between EBV-positive HL and genetic [...]

Factors involved in determining whether infectious mononucleosis occurs after primary EBV infection may include age, dose of virus received, and various genetic markers. A study by McAulay and colleagues reported [...]