The Signal Sequence of Lymphocytic Choriomeningitis Virus Contains an Immunodominant Cytotoxic T Cell Epitope That Is Restricted by both H-2Dband H-2KbMolecules

AbstractInfection of H-2bmice with lymphocytic choriomeningitis virus (LCMV) generates three well-characterized H-2Db-restricted immunodominant epitopes delineated in the NP, GP1, and GP2 proteins. Here we report that the H-2Db-restricted GP1 epitope GP33-41/43 (KAVYNFATC/GI) located in the signal sequence of LCMV is also the immunodominant epitope recognized by CTL at the surface of the same infected cells in the context of H-2Kbrestriction. The GP1 epitope bound to H-2Dband H-2Kbmolecules with comparable affinities. The respective binding processes involved different sets of peptide anchoring residues and required dramatically different conformations of the peptide backbone as well as rearrangement of residue side chains. The 10-mer peptide GP34-43 (AVYNFATCGI) was the optimal H-2Kb-binding sequence and the 8-mer peptide GP34-41 (AVYNFATC) the minimal sequence for optimal H-2Kb-restricted CTL recognition. Comparison of lytic activities of primary splenic anti-LCMV CTL from C57BL/6 (Db+/Kb+), B10A.[5R] (Db−/Kb+), and B10A.[2R] (Db+/Kb−) mice against LCMV-infected or peptide-coated target cells expressing either one or the two MHC alleles revealed that the H-2Kb-restricted component of the anti-GP1 CTL response was mounted independently of but as efficiently as its H-2Dbcounterpart. Analysis of the immune response against a GP1 variant that escapes CTL recognition showed that the GP1 epitope: (i) was likely the only immunodominant LCMV epitope in the context of H-2Kb, and (ii) could efficiently evade H-2Dband H-2Kb-restricted CTL mediated lysis

Electron microscopy analysis of FcRγ localization after its capture by T cells by trogocytosis

T cells acquire various proteins from their cellular partners by the process of trogocytosis. We recently demonstrated that the FcγRIIIA receptor and its associated FcRγ are captured by T cells during their co-culture with FcγR-expressing target cells upon both antigen- or antibody-mediated stimulation. Interestingly, we found that FcR captured by T cells could bind ligands but did not transmit detectable intracellular signals or signaling-depending functions upon ligand binding suggesting their improper integration in the recipient T cell membrane. In this study, we provide morphological data in support of this hypothesis. Indeed, we show that the FcRγ-subunit, which we used as a fusion to GFP, was clearly present at the plasma membrane of donor cells, but was detected within structures that were in close contact of, but apparently not integrated in, the plasma membrane of recipient T cells

Could CD4 Capture by CD8+ T Cells Play a Role in HIV Spreading?

CD8+ T cells have been shown to capture plasma membrane fragments from target cells expressing their cognate antigen, a process termed “trogocytosis”. Here, we report that human CD4, the Human Immunodeficiency Virus (HIV) receptor, can be found among the proteins transferred by trogocytosis. CD4 is expressed in a correct orientation after its capture by CD8+ T cells as shown by its detection using conformational antibodies and its ability to allow HIV binding on recipient CD8+ T cells. Although we could not find direct evidence for infection of CD8+ T cells having captured CD4 by HIV, CD4 was virologically functional on these cells as it conferred on them the ability to undergo syncytia formation induced by HIV-infected MOLT-4 cells. Our results show that acquisition of CD4 by CD8+ T cells via trogocytosis could play a previously unappreciated role for CD8+ T cells in HIV spreading possibly without leading to their infection

Preferential Transfer of Certain Plasma Membrane Proteins onto T and B Cells by Trogocytosis

T and B cells capture antigens via membrane fragments of antigen presenting cells (APC) in a process termed trogocytosis. Whether (and how) a preferential transfer of some APC components occurs during trogocytosis is still largely unknown. We analyzed the transfer onto murine T and B cells of a large panel of fluorescent proteins with different intra-cellular localizations in the APC or various types of anchors in the plasma membrane (PM). Only the latter were transferred by trogocytosis, albeit with different efficiencies. Unexpectedly, proteins anchored to the PM's cytoplasmic face, or recruited to it via interaction with phosphinositides, were more efficiently transferred than those facing the outside of the cell. For proteins spanning the PM's whole width, transfer efficiency was found to vary quite substantially, with tetraspanins, CD4 and FcRγ found among the most efficiently transferred proteins. We exploited our findings to set immunodiagnostic assays based on the capture of preferentially transferred components onto T or B cells. The preferential transfer documented here should prove useful in deciphering the cellular structures involved in trogocytosis

The Host Microbiota Contributes to Early Protection Against Lung Colonization by Mycobacterium tuberculosis

Tuberculosis (TB), caused by the airborne bacterial pathogen Mycobacterium tuberculosis, remains a major source of morbidity and mortality worldwide. So far, the study of host-pathogen interactions in TB has mostly focused on the physiology and virulence of the pathogen, as well as, on the various innate and adaptive immune compartments of the host. Microbial organisms endogenous to our body, the so-called microbiota, interact not only with invading pathogens, but also with our immune system. Yet, the impact of the microbiota on host defense against M. tuberculosis remains poorly understood. In order to address this question, we adapted a robust and reproducible mouse model of microbial dysbiosis based on a combination of wide-spectrum antibiotics. We found that microbiota dysbiosis resulted in an increased early colonization of the lungs by M. tuberculosis during the first week of infection, correlating with an altered diversity of the gut microbiota during this time period. At the cellular level, no significant difference in the recruitment of conventional myeloid cells, including macrophages, dendritic cells and neutrophils, to the lungs could be detected during the first week of infection between microbiota-competent and -deficient mice. At the molecular level, microbiota depletion did not impact the global production of pro-inflammatory cytokines, such as interferon (IFN)γ, tumor necrosis factor (TNF)α and interleukin (IL)-1β in the lungs. Strikingly, a reduced number of mucosal-associated invariant T (MAIT) cells, a population of innate-like lymphocytes whose development is known to depend on the host microbiota, was observed in the lungs of the antibiotics-treated animals after 1week of infection. These cells produced less IL-17A in antibiotics-treated mice. Notably, dysbiosis correction through the inoculation of a complex microbiota in antibiotics-treated animals reversed these phenotypes and improved the ability of MAIT cells to proliferate. Altogether, our results demonstrate that the host microbiota contributes to early protection of lung colonization by M. tuberculosis, possibly through sustaining the function(s) of MAIT cells. Our study calls for a better understanding of the impact of the microbiota on host-pathogen interactions in TB. Ultimately, this study may help to develop novel therapeutic approaches based on the use of beneficial microbes, or components thereof, to boost anti-mycobacterial immunity

Inmunomedia 4.0: enseñando y aprendiendo Inmunología. Una experiencia interuniversitaria vertebrada en 4 ejes

El nuevo profesor-tutor desempeña competencias que incluyen el uso de las nuevas tecnologías, el diseño de Objetos de Aprendizaje Multimedia (OAM) y la supervisión del aprendizaje del alumnado. En este contexto, Inmunomedia 4.0 –proyecto en el que participan las Universidades de Valladolid, Alicante, Complutense y Toulouse III- pretende responder a necesidades y carencias en la docencia de la Inmunología en titulaciones Biomédicas: en primer lugar “Elaborando y difundiendo OAMs" de Inmunología de calidad, como la colección de “Inmunopíldoras” de gran impacto entre universitarios hispanoparlantes; en segundo lugar "Coleccionando OAMs en tablones" (“Content Curation”) que proporcionan a estudiantes y profesores información útil, etiquetada, contrastada y organizada por Módulos. De las diferentes herramientas de “content curation” utilizadas, las de mayor repercusión han sido las colecciones realizadas con “Scoop.it” y “Pinterest”; en tercer lugar "Implicando activamente a los estudiantes" de diferentes universidades en la elaboración de un “Periódico Universitario de Inmunología” tras emitir en twitter noticias de interés inmunológico usando hashtags, que se rastrean y generan un diario en “Paper.li”; y finalmente "Impulsando la tercera misión universitaria" elaborando materiales divulgativos multimedia de inmunología y difundiéndolos en redes sociales, a los pacientes e incluso en lugares públicos (colección de videos “Canal Defensas”)

Étude des caractéristiques de la capture de fragments de membrane par trogocytose par les lymphocytes T et B

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Molecular signature of recent thymic selection events on effector and regulatory CD4+ T lymphocytes.

International audienceNatural CD4+CD25+ regulatory T lymphocytes (Treg) are key protagonists in the induction and maintenance of peripheral T cell tolerance. Their thymic origin and biased repertoire continue to raise important questions about the signals that mediate their development. We validated analysis of MHC class II capture by developing thymocytes from thymic stroma as a tool to study quantitative and qualitative aspects of the cellular interactions involved in thymic T cell development and used it to analyze Treg differentiation in wild-type mice. Our data indicate that APCs of bone marrow origin, but, surprisingly and importantly, not thymic epithelial cells, induce significant negative selection among the very autoreactive Treg precursors. This fundamental difference between thymic development of regulatory and effector T lymphocytes leads to the development of a Treg repertoire enriched in cells specific for a selected subpopulation of self-Ags, i.e., those specifically expressed by thymic epithelial cells