Search

T cell activation and function require a structured engagement of antigen-presenting cells. These cell contacts are characterized by two distinct dynamics in vivo: transient contacts resulting from promigratory junctions called immunological kinapses or prolonged contacts from stable junctions called immunological synapses. Kinapses operate in the steady state to allow referencing to self-peptide-MHC (pMHC) and searching for pathogen-derived pMHC. Synapses are induced by T cell receptor (TCR) interactions with agonist pMHC under specific conditions and correlate with robust immune responses that generate effector and memory T cells. High-resolution imaging has revealed that the synapse is highly coordinated, integrating cell adhesion, TCR recog- nition of pMIC complexes, and an array of activating and inhibitory ligands to promote or prevent T cell signaling. In this review, we examine the molecular components, geometry, and timing underlying kinapses and synapses. We integrate recent molecular and physiological data to provide a synthesis and suggest ways forward. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) in lymphoid tissue arise from precursors that also produce monocytes and plasmacytoid DCs (pDCs). Where DC and monocyte lineage commitment occurs and the nature of the DC precursor that migrates from the bone marrow to peripheral lymphoid organs are unknown. We show that DC development progresses from the macrophage and DC precursor to common DC precursors that give rise to pDCs and classical spleen DCs (cDCs), but not monocytes, and finally to committed precursors of cDCs (pre-cDCs). Pre-cDCs enter lymph nodes through and migrate along high endothelial venules and later disperse and integrate into the DC network. Further cDC development involves cell division, which is controlled in part by regulatory T cells and fins-like tyrosine kinase receptor-3. [ABSTRACT FROM AUTHOR]

T helper cells that produce IL-17 (TH17 cells) promote autoimmunity in mice and have been implicated in the pathogenesis of human inflammatory diseases. At mucosal surfaces, TH17 cells are thought to protect the host from infection, whereas regulatory T (Treg) cells control immune responses and inflammation triggered by the resident microflora. Differentiation of both cell types requires transforming growth factor-β (TGF-β), but depends on distinct transcription factors: RORγt (encoded by Rorc(γt)) for TH17 cells and Foxp3 for Treg cells. How TGF-β regulates the differentiation of T cells with opposing activities has been perplexing. Here we demonstrate that, together with pro-inflammatory cytokines, TGF-β orchestrates TH17 cell differentiation in a concentration-dependent manner. At low concentrations, TGF-β synergizes with interleukin (IL)-6 and IL-21 (refs 9–11) to promote IL-23 receptor (Il23r) expression, favouring TH17 cell differentiation. High concentrations of TGF-β repress IL23r expression and favour Foxp3+ Treg cells. RORγt and Foxp3 are co-expressed in naive CD4+ T cells exposed to TGF-β and in a subset of T cells in the small intestinal lamina propria of the mouse. In vitro, TGF-β-induced Foxp3 inhibits RORγt function, at least in part through their interaction. Accordingly, lamina propria T cells that co-express both transcription factors produce less IL-17 (also known as IL-17a) than those that express RORγt alone. IL-6, IL-21 and IL-23 relieve Foxp3-mediated inhibition of RORγt, thereby promoting TH17 cell differentiation. Therefore, the decision of antigen-stimulated cells to differentiate into either TH17 or Treg cells depends on the cytokine-regulated balance of RORγt and Foxp3. [ABSTRACT FROM AUTHOR]

An essay is presented on fast evolution and somatic hypermutation of pathogens as RNA-based viruses. It offers an insight into the ability of antibodies of affinity binding and pinpoint precision to unlimited molecular structures. The author reveals the low potency of antigen which when come in contact with antibodies, fights and undergoes rapid evolution.

Dendritic cells (DCs) are uniquely capable of transporting tumor antigens to tumor-draining lymph nodes (tdLNs) and interact with effector T cells in the tumor microenvironment (TME) itself, mediating both natural antitumor immunity and the response to checkpoint blockade immunotherapy. Using LIPSTIC (Labeling Immune Partnerships by SorTagging Intercellular Contacts)-based single-cell transcriptomics, we identified individual DCs capable of presenting antigen to CD4 + T cells in both the tdLN and TME. Our findings revealed that DCs with similar hyperactivated transcriptional phenotypes interact with helper T cells both in tumors and in the tdLN and that checkpoint blockade drugs enhance these interactions. These findings show that a relatively small fraction of DCs is responsible for most of the antigen presentation in the tdLN and TME to both CD4 + and CD8 + tumor-specific T cells and that classical checkpoint blockade enhances CD40-driven DC activation at both sites.

Immunization with mosaic-8b [60-mer nanoparticles presenting 8 SARS-like betacoronavirus (sarbecovirus) receptor-binding domains (RBDs)] elicits more broadly cross-reactive antibodies than homotypic SARS-CoV-2 RBD-only nanoparticles and protects against sarbecoviruses. To investigate original antigenic sin (OAS) effects on mosaic-8b efficacy, we evaluated effects of prior COVID-19 vaccinations in non-human primates and mice on anti-sarbecovirus responses elicited by mosaic-8b, admix-8b (8 homotypics), or homotypic SARS-CoV-2 immunizations, finding greatest cross-reactivity for mosaic-8b. As demonstrated by molecular fate-mapping in which antibodies from specific cohorts of B cells are differentially detected, B cells primed by WA1 spike mRNA-LNP dominated antibody responses after RBD-nanoparticle boosting. While mosaic-8b- and homotypic-nanoparticles boosted cross-reactive antibodies, de novo antibodies were predominantly induced by mosaic-8b, and these were specific for variant RBDs with increased identity to RBDs on mosaic-8b. These results inform OAS mechanisms and support using mosaic-8b to protect COVID-19 vaccinated/infected humans against as-yet-unknown SARS-CoV-2 variants and animal sarbecoviruses with human spillover potential., Competing Interests: DECLARATION OF INTERESTS P.J.B. and A.A.C. are inventors on a US patent application (17/523,813) filed by the California Institute of Technology that covers the mosaic nanoparticles described in this work. A.I.R. and J.D.P. are inventors on a US patent (11,780,888) that covers the chimeric sequence of RBD fused to the HA2 stem of influenza hemagglutinin. A.J.G. is an inventor on a Fred Hutchinson Cancer Center-optioned technology related to DMS of the RBD of SARS-CoV-2 spike protein. L.M., S.B., R.C., C.S-A., and I.G.F. are inventors on U.S. Patent Applications (16/952,983) and (17/651,476) filed by Ingenza Ltd. that cover Bacillus and Pichia strains established to manufacture endotoxin-free vaccine products. J.H.E. is an employee of HDT Bio that provided the repRNA-LION vaccine. D.H.F. is a co-founder of Orlance, Inc. that is developing gene gun delivery of DNA and repRNA vaccines. S.B., R.C., M.Q.-A., E.R., C.S.-A., L.M., and I.G.F. are employees of Ingenza, LTD. P.J.B. and G.D.V. are scientific advisors for Vaccine Company, Inc, and P.J.B. is a scientific advisor for Vir Biotechnology. N.P. is named on patents describing the use of nucleoside-modified mRNA in lipid nanoparticles as a vaccine platform. N.P. served on the mRNA strategic advisory board of Sanofi Pasteur in 2022 and the mRNA technology advisory board of Pfizer in 2023 and is a member of the Scientific Advisory Board of AldexChem and Bionet-Asia. P.J.C.L. is an employee of Acuitas Therapeutics, a company developing LNP delivery systems for RNA therapeutics.

Interactions between different cell types are key for immune function. Traditionally, interactions have been investigated in vivo by intravital two-photon microscopy, but the molecular characterization of the cells participating in a specific interaction is limited by the inability to retrieve the cells for downstream analysis. We recently developed an approach to label cells undergoing specific interactions in vivo, which we called LIPSTIC (Labeling Immune Partnership by Sortagging Intercellular Contacts). Here, we provide detailed instructions on how to track CD40-CD40L interactions between dendritic cells (DCs) and CD4 + T cells using genetically engineered LIPSTIC mice. This protocol requires expertise in animal experimentation and multicolor flow cytometry. Once mouse crossing has been achieved, it takes 3 days or more to complete, depending on the kinetics of the interactions that the researcher wishes to investigate., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

The gut epithelium is populated by intraepithelial lymphocytes (IELs), a heterogeneous T cell population with cytotoxic and regulatory properties, which can be acquired at the epithelial layer. However, the role of T cell receptor (TCR) in this process remains unclear. Single-cell transcriptomic analyses revealed distinct clonal expansions between cell states, with CD4 + CD8αα + IELs being one of the least diverse populations. Conditional deletion of TCR on differentiating CD4 + T cells or of major histocompatibility complex (MHC) class II on intestinal epithelial cells prevented CD4 + CD8αα + IEL differentiation. However, TCR ablation on differentiated CD4 + CD8αα + IELs or long-term cognate antigen withdraw did not affect their maintenance. TCR re-engagement of antigen-specific CD4 + CD8αα + IELs by Listeria monocytogenes did not alter their state but correlated with reduced bacterial invasion. Thus, local antigen recognition is an essential signal for differentiation of CD4 + T cells at the epithelium, yet differentiated IELs are able to preserve an effector program in the absence of TCR signaling., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Most broadly neutralizing antibodies to HIV-1 have in common an extreme degree of somatic hypermutation (SHM), which correlates with their ability to neutralize multiple viral strains. However, achieving such extreme SHM by immunization remains a challenge. Here, we discuss how antigenic variation during HIV-1 infection may work to exacerbate SHM by permitting multiple iterative cycles of affinity maturation in germinal centers, and speculate on how this could be recapitulated through vaccination., (Copyright © 2018 Cold Spring Harbor Laboratory Press; all rights reserved.)

Germinal centers (GCs) are inducible microanatomical structures required for the generation of high-affinity antibodies. Migration of B and T cells within and into/out of GCs plays a key role in the evolutionary process that underlies affinity maturation, and thus microanatomical location of cells is an important variable when studying GC processes. We describe a protocol in which in situ photoactivation by multiphoton microscopy can be used to add microanatomical information to flow cytometry, allowing for identification and isolation of GC cells based on their location. Cells in different microanatomical compartments can then be sorted and analyzed for surface marker and mRNA expression.

Antibodies are currently the fastest-growing class of therapeutics. Although naked antibodies have proven valuable as pharmaceutical agents, they have some limitations, such as low tissue penetration and a long circulatory half-life. They have been conjugated to toxic payloads, PEGs, or radioisotopes to increase and optimize their therapeutic efficacy. Although nonspecific conjugation is suitable for most in vitro applications, it has become evident that site specifically modified antibodies may have advantages for in vivo applications. Herein we describe a novel approach in which the antibody fragment is tagged with two handles: one for the introduction of a fluorophore or (18)F isotope, and the second for further modification of the fragment with a PEG moiety or a second antibody fragment to tune its circulatory half-life or its avidity. Such constructs, which recognize Class II MHC products and CD11b, showed high avidity and specificity. They were used to image cancers and could detect small tumors., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Germinal centers (GCs) are the site of maturation of antibody affinity and are thus of key importance to humoral immunity. The study of B-cell dynamics and selection within the GC has been hampered by the limited number of techniques available to manipulate GC output in vivo. Here, we describe an approach to trigger positive selection of B cells in vivo by targeting antigen specifically to a subpopulation of GC B cells via the surface lectin DEC-205 and forcing their interaction with T follicular helper cells. Targeted GC B cells can then be followed over time as they progress through the stages of positive selection.

T helper cells that produce IL-17 (T(H)17 cells) promote autoimmunity in mice and have been implicated in the pathogenesis of human inflammatory diseases. At mucosal surfaces, T(H)17 cells are thought to protect the host from infection, whereas regulatory T (T(reg)) cells control immune responses and inflammation triggered by the resident microflora. Differentiation of both cell types requires transforming growth factor-beta (TGF-beta), but depends on distinct transcription factors: RORgammat (encoded by Rorc(gammat)) for T(H)17 cells and Foxp3 for T(reg) cells. How TGF-beta regulates the differentiation of T cells with opposing activities has been perplexing. Here we demonstrate that, together with pro-inflammatory cytokines, TGF-beta orchestrates T(H)17 cell differentiation in a concentration-dependent manner. At low concentrations, TGF-beta synergizes with interleukin (IL)-6 and IL-21 (refs 9-11) to promote IL-23 receptor (Il23r) expression, favouring T(H)17 cell differentiation. High concentrations of TGF-beta repress IL23r expression and favour Foxp3+ T(reg) cells. RORgammat and Foxp3 are co-expressed in naive CD4+ T cells exposed to TGF-beta and in a subset of T cells in the small intestinal lamina propria of the mouse. In vitro, TGF-beta-induced Foxp3 inhibits RORgammat function, at least in part through their interaction. Accordingly, lamina propria T cells that co-express both transcription factors produce less IL-17 (also known as IL-17a) than those that express RORgammat alone. IL-6, IL-21 and IL-23 relieve Foxp3-mediated inhibition of RORgammat, thereby promoting T(H)17 cell differentiation. Therefore, the decision of antigen-stimulated cells to differentiate into either T(H)17 or T(reg) cells depends on the cytokine-regulated balance of RORgammat and Foxp3.