bluuebunny/crossref_metadata_2025_split huggingface dataset:
HLA-DO promotes bacterial superantigen binding to MHC class II molecules (106.27)
Authors: Pezeshki Abdul Mohammad , Azar Georges , Denzin Lisa , Mourad Walid , Thibodeau Jacques 
Published: January 2023

Abstract
HLA-DO (H2-O in mice) is an intracellular non-classical MHC class II molecule. It forms a stable complex with HLA-DM (H2-M in mice) and by regulating its activity shapes the peptide repertoire. Using a stable cell line overexpressing HLA-DO (HeLa-CIITA-DO), we show here that HLA-DO improved binding of SEA and TSST-1 superantigens (SAgs) to MHC class II molecules. Binding of SEB was not affected in these conditions. Exogenous pulsing of Class II-associated invariant chain peptide (CLIP) elucidate that CLIP is a major player in this process. Accordingly, HLA-DO knock-down using specific siRNA, decreased SEA and TSST-1 binding in HeLa-CIITA-DO cells. Furthermore, silencing of DM increased SEA and TSST-1 binding in HeLa-CIITA and 293-CIITA cells. Shutting down of Ii reversely decreased binding of SEA and TSST-1 in 293-CIITA cells. However, in HeLa-CIITA, Ii depletion just decreased SEA binding but does not affect TSST-1 binding. H2-O did not show the same boosting effect on SAgs binding in splenocytes. In conclusion, our results show that HLA-DO can improve SEA and TSST-1 binding in line with a role for CLIP in SAgs binding.
HLA-DO and its effect on peptide binding to MHC Class II (106.29)
Authors: Poluektov Yuri , Kim AeRyon , Sadegh-Nasseri Scheherazade 
Published: January 2023

Abstract
True function of HLA-DO (DO), an MHC Class II accessory molecule remains a mystery. The leading model on it function proposes that DO inhibits the effects of DM. Most of those studies were have used in vivo mouse models, looking at the endpoint of peptide presentation, not taking into account the individual steps in the process. To directly study DO function, we designed a recombinant soluble DO that included leucine zipper for better dimerization of the DOα- and β- chains and expressed it in insect cells. Kinetic experiments involving DR1 and the peptide with or without DM and DO revealed unexpected results. We found that; a) DO diminishes the binding of two peptides that are DM-sensitive, b)DO has positive effects on binding of peptides that form DM-resistant complexes, c) DO only has an effect on peptide association and virtually no effect on peptide dissociation, and d) DO functionsdirectly on DR molecules.We propose that DO binds to the peptide-receptive MHC II molecules that DM generates either by dissociating the bound peptides, or opening of the empty groove. The role for DO then is to enforce another layer of control on peptide selection. In support of this hypothesis, using BIACore Surface Plasmon Resonance, we have measured direct binding of DO to an open conformation of HLA-DR1 in real time, while no binding to a closed DR1 conformation wasdetected.
miRNAs regulate epidermal Langerhans cell cross-presentation (106.3)
Authors: Mi Qing-Sheng , Xu Ying-Ping , Qi Rui-Qun , Zhou Li 
Published: January 2023

Abstract
Langerhans cells (LCs) are skin-residential dendritic cells (DCs) with a life cycle distinct from other types of DCs and place very important roles in skin immunity and tolerance. MicroRNAs (miRNAs), evolutionarily conserved small non-coding RNAs that repress target genes, regulate immune cell development and function. Recent studies from our laboratory and others indicated that miRNA deletion in DC-lineage interrupts the homeostasis and function of epidermal LCs with normal conventional DCs, suggesting that miRNAs are required for LC development and function. However, the roles of individual miRNAs in regulating LC development and function are still completely unknown. miRNAs miR-150 and miR-223 are highly expressed in mature lymphocytes and myeloid cells, respectively. We have found that miR-150 and miR-223 are also expressed in LCs and the expression of miR-150 is significantly down-regulated during in vitro LC maturation. Using miR-150 and miR-223 knockout mouse models, we have found that lack of miR-150 or lack of miR-223 does not disturb the development, maturation, migration and phagocytic capacity of epidermal LCs. However, lack of miR-150 significantly reduces the capacity of LCs to cross-present a soluble antigen to antigen-specific CD8+ T cells, while lack of miR-233 significantly increases the capacity of LC cross-presentation. Thus, our data indicate that miR-150 and miR-223 are not required for LC development, but differentially regulate LC cross-presentation.
Tapasin-assisted peptide loading and the nature of the HLA-A2(T134K) assembly defect (106.36)
Authors: Rizvi Syed , Raghavan Malini 
Published: January 2023

Abstract
MHC class I molecules are assembled in endoplasmic reticulum (ER) with the help of a peptide loading complex (PLC). The PLC includes specific assembly factors, the transporters associated with antigen processing (TAP) and tapasin, and generic ER chaperones, calreticulin and ERp57. Previous studies have shown that the T134K mutation of HLA-A2 (A2) interferes with cell-surface expression. It has been suggested that reduced cell-surface expression of A2(T134K) is due to impaired interactions of A2(T134K) with tapasin. We expressed the A2(T134K) in a tapasin-deficient cell line (M553), and compared assembly and surface expression of the mutant relative to that of wild-type A2. In M553 cells, the A2(T134K) was profoundly impaired in tapasin-induced cell surface expression. Surprisingly, the A2(T134K) was able to bind to tapasin and TAP. However, compared with A2, assembly of A2(T134K) with β2m was reduced, and ER retention of the mutant was correspondingly enhanced, consistent with impairment in intracellular peptide loading. Similar association kinetics were observed for the interactions of purified empty soluble versions of A2 or A2(T134K) with peptides. On the other hand, both peptide-deficient and peptide-loaded forms of the A2(T134K) were found to be more thermostable compared to wild-type A2. These findings indicate that stabilizing conformational changes induced by the A2(T134K) mutation interfere with tapasin-assisted optimization of the A2(T134K) peptide repertoire.
Murine MHC class Ib gene T11: a functional paralog of T23/Qa-1? (106.42)
Authors: Chen Lili , He Xiao , Kumanovics Attila , Fairbanks Jared , Jensen Peter 
Published: January 2023

Abstract
MHC class Ia molecules, H2-K/D/L in mouse, select CD8 T cells during development and present peptides to appropriate CD8 T cells in immune responses. Mouse MHC class Ib H2-Q, T, M regions contain more than 20 protein-encoding genes, but only few have been studied. Qa-1, encoded by H2-T23 gene, is one of the best-studied MHC class Ib. Qa-1 presents peptide generated from MHC Ia to NKG2A/CD94 receptors and provides inhibitory signal to NK cells. Here, we report the study of another MHC class Ib gene, H2-T11. T11 is 95% identical in DNA level and 87% identical in protein level to T23. T11 mRNA was detected in spleen, thymus and uterus in B6 mice, and its expression pattern is more limited than that of T23. Recombinant T11 was refolded with β2m, with or without the exogenous Qdm peptides. The refolded T11 had a typical secondary structure of MHC class I proteins, shown by circular dichroism analysis. The refolded T11 bound Qdm in vitro and could be recognized by a Qa-1 specific mAb. T11 was ectopically expressed on the surface of several cell lines, including a Tap deficient one. The T11 expressing cells could not present insulin to Qa-1 restricted, insulin-specific T cell hybridoma, in contrast to T23 expressing cells. Our results indicated that despite a high similarity to T23, T11 might have different function from T23/Qa-1. We are in the process of eluting naturally bound peptides from T11 expressing cells, and using T11/Qdm tetramers to look for its potential ligand(s).
Characterization of a human CD1d-knockin mouse (106.44)
Authors: Yuan Weiming , Wen Xiangshu , Rao Ping , Kim Seil , Cresswell Peter 
Published: January 2023

Abstract
CD1d-restricted natural killer T (NKT) cells regulate the immune system in response to a broad range of diseases. The CD1d/NKT antigen presentation pathway is largely conserved between human and mouse, however, there is distinct difference between the two species. To better study human CD1d antigen presentation in an in vivo setting, we have generated a human CD1d knock-in (KI) mouse. We have expressed human CD1d (hCD1d) in place of mouse CD1d (mCD1d). The expression of hCD1d was verified on CD4+CD8+DP thymocytes and thymic dendritic cells, which are involved in NKT cell positive and negative selections, respectively, in thymus. CD1d-α-GalCer tetramer+ invariant NKT (iNKT) cells have been shown in thymus, spleen and liver. However, reduced numbers of iNKT cells were observed in these organs compared to that in wild-type mice. Among these iNKT cells, Vβ8 has been over-represented comparing with wild-type mouse, suggesting hCD1d preferentially selects for mouse Vβ8 chain, which is highly homologous to human Vβ11 chain. In vitro presentation of various glycolipids by BMDCs from hCD1d KI mice showed that hCD1d is functional in presenting different groups of lipids. Furthermore, lipid administration in the KI mice showed that in vivo hCD1d-restricted NKT cells are functional. In summary, our hCD1d KI mouse can be a novel model for in vivo studying hCD1d-specific antigen presentation in antitumor and antimicrobial immunity as well as autoimmune diseases.
Similar repertoires of T follicular helper and conventional CD4 T cells are generated in response to protein immunization. (P772) (106.47)
Authors: Leddon Scott , Sant Andrea 
Published: January 2023

Abstract
T follicular helper (Tfh) cells potentiate high-affinity, class-switched B cell responses, the predominant correlate of protection for vaccines. However, little is known about the epitope specificities of Tfh cells generated during polyclonal responses. To date, studies of epitope-specific Tfh cells have relied on either the transfer of TcR transgenic cells or assays involving reagents to stain TcR (tetramer or antibody). In order to comprehensively evaluate polyclonal responses generated from the natural endogenous TcR repertoire, we developed a sorting strategy to separate Tfh cells from CD44highnon-Tfh cells and measured epitope-specific responses with cytokine-specific ELISPOT assays. The immunodominance hierarchies of both Tfh and non-Tfh cells generated in response to immunization with several model antigens (MalE, HEL, and OVA) were remarkably similar. Strikingly, the frequency of cytokine producing Tfh cells at the peak of expansion, independent of the epitope measured, was approximately 6 to 12-fold higher then non-Tfh cells. In agreement with previous studies of unfractionated CD4 cells from our group, increasing the kinetic stability of peptide-MHC class II complexes enhances the priming of Tfh cells. By understanding the parameters that control epitope specific priming, vaccines may be tailored to enhance or focus Tfh responses to facilitate optimal B cell responses.
A novel form of T cell antagonism by trapping of immunological synapse (106.49)
Authors: Carreño Leandro , Riquelme Erick , González Pablo , Espagnolle Nicolas , Riedel Claudia , Valitutti Salvatore , Kalergis Alexis 
Published: January 2023

Abstract
T cell activation results from productive T cell receptor (TCR) engagement by a cognate peptide-MHC (pMHC) complex on the antigen presenting cell (APC) surface, a process leading to the polarization of the T cell secretory machinery towards the interface of APC. We have previously shown that the half-life of the TCR/pMHC interaction and the density of pMHC on the APC are two parameters determining T cell activation. Here, by using APLs conferring different half-lives to the TCR/pMHC interaction we have tested how this parameter can control T cell polarization. We observed that only TCR/pMHC interactions with intermediate half-lives can promote the assembly of synapses that lead to T cell activation. Strikingly, intermediate half-life interactions can be competed out by short half-life interactions, which can efficiently promote T cell polarization and antagonize T cell activation that was induced by activating intermediate half-life interactions. However, short TCR/pMHC interactions fail at promoting phosphorylation of signaling molecules at the T cell-APC contact interface, which are needed for T cell activation. Our data suggest that while intermediate half-life pMHC ligands promote assembly of activating synapses, this process can be inhibited by short half-life antagonistic pMHC ligands, which promote the assembly of non activating synapses.
Particles such as an asian sand dust activate autophagic and apoptotic key molecules in CD11b positive cells. (106.6)
Authors: Yoshida Yasuhiro , Song Yuan , Ichinose Takamichi 
Published: January 2023

Abstract
Asian sand dust (ASD) is derived from air pollutants in East China and has a long history of appearing in Japan. Recently, it is knowing that ASD contains microbial materials, sulfate (SO(4)(2-)) and nitrate (NO(3)(-)), therefore there is increasing concern for its possible adverse health effects. Although it has been reported that ASD induces inflammatory responses in the lung tissue and causes respiratory diseases such as eosinophilia in mice, the effect of ASD on the peripheral lymphoid organ are not fully understood. In this study, we examine the effect of ASD on immune system. ICR mice were administered intratracheal ASD (0, 0.2, 0.02 mg/mice), and were sacrificed at 4 weeks (1 time per week and total 4 times) after administration. Spleen cells were prepared and cell lysates of splenocytes were resolved in western blotting. Immuno-blotting demonstrated that ASD induced autophagic-maker LC3 and p62 expression and also induced PARP cleavage suggesting caspase-dependent apoptosis in splenocytes. In addition, ASD could increase the expression of TNF-α mRNA analyzed by Real-time PCR. As same as in vivo, we observed ASD enhanced TNF-α production induced by ConA in splenocytes. Taken together, ASD induced systemic inflammation resulting in autophagic and apoptotic phenomena in splenocytes, suggesting that ASD administration not only triggered pulmonary inflammation but also affected peripheral lymphoid tissue.
The human invariant chain p35 favors formation of nonameric complexes with MHC class II molecules (107.1)
Authors: Cloutier Maryse , Fortin Jean-Simon , Thibodeau Dr Jacques 
Published: January 2023

Abstract
The invariant chain (Ii) associates with MHCII alpha beta (αβ) chains after biosynthesis. Although previous studies described (αβIi)3 nonameric complexes, a recent report suggested that Ii trimers could only bind a single MHCII heterodimer at once. (Roche et al, 1991, Koch et al, 2011) We have investigated this discrepancy in the context of two human Ii isoforms, p33 and p35. The latter includes an ER retention motif (RXR) that is masked by MHCII β cytoplasmic tail upon its association with Ii. Using transfected HEK293T cells and flow cytometry, we monitored ER egress of various combinations of MHCII and Ii variants. First, we showed that MHCII only masked Ii RXR motif if associated directly (in cis) to the p35 subunit. Second, our results indicated that while p33 homotrimers may exit the ER as pentamer with one MHCII, p35-p33 mixed-trimers require cis masking of every Ii RXR motif before egress, thereby favoring heptamers and nonamers formation. Indeed, sucrose gradient of cell extracts confirmed larger complexes with p35 compared to p33. Altogether, our data argue for a kinetic model in which p33 homotrimers are free to exit the ER at any time, independently of the number of associated MHCII. In contrast, ER retention of Ii trimer containing p35 allows for binding of multiple MHCII until every RXR motifs are inactivated.
HCV and HIV stimulate production of the inflammatory cytokine IL-18 through activation of the Nalp3 inflammasome in monocytes (108.12)
Authors: Chattergoon Michael , Levine Jordana , Cox Andrea 
Published: January 2023

Abstract
Activation of the inflammasome-complex leads to production of the pro-inflammatory, inflammasome-associated cytokines IL-18 and IL-1β. These cytokines amplify the innate antiviral immune response and skew the developing adaptive immune response. We previously reported that IL-18 is the earliest host response to hepatitis C virus (HCV) infection and remains elevated at low levels in chronic infection. Our group has also reported an association between IL-18 SNPs and likelihood of HCV clearance. Despite these observations, the role of IL-18 in control of viruses capable of chronic infection is unknown. We now show that IL-18 is also elevated in persons with uncontrolled HIV and to a lesser extent in those with natural immunologic control of the virus. To understand inflammasome activity during chronic viral infection, we studied the interaction of HCV or HIV infected plasma and PBMC subsets from HIV and HCV uninfected subjects. We determined that (1) monocytes cultured with plasma from HIV or HCV viremic individuals produce IL-18 and other pro-inflammatory cytokines; (2) the virion is the inflammasome stimulating component within plasma, (3) siRNA knockdown of Nalp3 in monocytes modulates HCV and HIV induction of IL-18. Our data elucidate mechanisms by which HCV and HIV activate the inflammasome complex and demonstrate the production of inflammatory cytokines through the interaction of HIV and HCV and monocytes.
NEMO recruitment of polyubiquitinated TBK1 to MAVS builds signalosome to regulate innate anti-viral immunity (108.3)
Authors: Wang Lingyan , Li Shitao , Berman Michael , Kong Young-Yun , Dorf Martin 
Published: January 2023

Abstract
RIG-I-like receptors (RLRs) are intracellular sensors utilized by nearly all cell types for recognition of viral RNA, initiation of antiviral defense, and induction of type I interferons (IFN). TBK1 is a critical kinase implicated in RLR-dependent IFN transcription. The E3 ligases Mind bomb 1 (MIB1) and Mind bomb 2 (MIB2) conjugate TBK1 with K63-linked polyubiquitin on residues K69 and K154. TBK1 polyubiquitination is critical for recruitment of the downstream adaptor, NEMO. After viral infection NEMO and IRF3 are independently recruited to MAVS. NEMO bridges TBK1 to MAVS through ubiquitin binding domains. The assembly of the NEMO/TBK1 complex on MAVS leads to activation of TBK1 kinase activity and phosphorylation of the transcription factor, IRF3. In contrast, activation of NF-kB is not impaired by MIB deficiency. The combined results refine current views of RLR signaling, define the role of TBK1 polyubiquitination and detail the assembly of the MAVS signalosome.
Bacterial DNA-induced anti-apoptotic c-IAP-2 protects human monocytic cells against HIV-Vpr-mediated mitochondrial membrane depolarization and apoptosis through TRAF 1/2 via sequential inhibition of pro-apoptotic Caspase 8, Bid and Bax (108.7)
Authors: Saxena Mansi , Busca Aurelia , Kumar Ashok 
Published: January 2023

Abstract
Monocytic cells are important HIV reservoirs and exhibit marked resistance to apoptosis upon infection, thereby hindering clearing of pathogens. However, the mechanism underlying the development of resistance to apoptosis in these cells is poorly understood. Using Vpr-52-96 amino acids peptide (Vpr), a HIV accessory protein, as a model for apoptosis, we have previously shown that prior treatment with CpG or E.coli DNA prevented Vpr-mediated apoptosis by induction of anti apoptotic c-IAP-2 gene via calmodulin-dependent kinase II (CAMK-II) activation in human monocytes and promonocytic THP-1 cells. Herein, we show that c-IAP-2 induced by bacterial DNA in a CaMK-II dependant manner, protects against Vpr-mediated mitochondrial depolarization. Vpr-induced mitochondrial depolarization and apoptosis is mediated by TRAF1/2 downregulation and subsequent activation of proapoptotic caspase-8, bid and bax. Treatment of cells with bacterial DNA, through c-IAP-2 induction, prevented these effects of Vpr, thereby protecting against Vpr-mediated mitochondrial depolarization and apoptosis. Overall, these results suggest a key role played by bacterial DNA-induced c-IAP-2 in preventing Vpr-mediated mitochondrial depolarization and apoptosis through prevention of TRAF 1/2 downregulation and sequential inhibition of caspase 8, bid and bax. Furthermore, strategies based on suppressing c-IAP-2 by targeting CaMK-II, TRAF1/2 or Caspase-8 may be helpful in controlling reservoir formation.
Altered class switch recombination junctions in patients with deficiency in Mlh1 and Brca1 (109.6)
Authors: Bjorkman Andrea , Du Likun , Lindblom Annika , Pan-Hammarstrom Qiang 
Published: January 2023

Abstract
Class switch recombination (CSR) is a B-cell specific process that results in the change of immunoglobulin isotype from IgM to IgA, IgG or IgE. It involves the creation of DNA double strand breaks (DSBs) in switch regions, which are sensed and repaired by DNA damage response proteins and the non-homologous end-joining (NHEJ) pathway. Here we have studied CSR in patients with heterozygous mutations in both the mismatch repair (MMR) gene Mlh1 and the breast cancer susceptibility gene Brca1 and in patients with mutations in either Mlh1 or Brca1 alone. Brca1 is involved in several processes ranging from DNA DSB repair, particularly through homologous recombination, and cell cycle checkpoint control to ubiquitination and chromatin remodeling. Its function in NHEJ as well as in CSR is unknown. The MMR pathway normally repairs mismatches arising in the DNA, while during CSR it seems to be involved in the creation of DSBs by processing of mismatches in the switch regions. To study CSR in the patients we have analyzed the in vivo generated recombination switch junctions, formed after the repair of two switch regions during CSR. We have found that the switch recombination junctions are altered in all patients, suggesting the importance of these proteins during CSR in human B cells.
Antigenic ligand density modulates execution of naïve CD8+ T cell response programme (110.1)
Authors: Gund Rupali , Ebenezer Chitra , Thyagarajan Krishnamurthy , Chaudhry Ashutosh , George Anna , Bal Vineeta , Rath Satyajit 
Published: January 2023

Abstract
Upon brief exposure to antigenic stimulation, naïve CD8+ T lymphocytes execute an autonomous programme of several rounds of proliferation and maturation into effector cytotoxic cells. We have studied the role of ligand density as a modifier of this program using T cell receptor (TCR)-transgenic CD8+ T cell activation by short-duration stimulation in vitro. Over the entire ligand density range studied, we observe a graded increase in the frequency of responder naïve T cells that upregulate the expression of CD69, an early activation marker. However, the levels of induced CD69 are similar at all ligand densities. When CD69+ T cells are purified at early stages and cultured, most undergo successive proliferation cycles, showing that the execution of the autonomous programme during CD8+ T cell response is independent of ligand density. However, at very low ligand densities, the efficiency with which CD69+ T cells enter proliferation is poor and slow, leading to lower cell yields. At these ligand densities, post-activation TCR internalization is also inefficient. At any given ligand density, if activated CD69+ T cells that have internalised TCR are separated from those that have not internalised TCR, TCR-high cells show a lag in proliferation regardless of the ligand density. Together, these data indicate that ligand density quantitatively modulates the lag phase of the autonomous proliferation-differentiation programme of CD8+ T cells via TCR internalization-dependent mechanism.