Faculty Bibliography
Searched for:
in-biosketch:yes
person:dustim01
Total Results:
399
Structural basis for RIFIN-mediated activation of LILRB1 in malaria
The Plasmodium species that cause malaria are obligate intracellular parasites, and disease symptoms occur as they replicate within human blood. Despite risking immune detection, the parasite delivers proteins that bind host receptors to infected erythrocyte surfaces. In the causative agent of the most deadly human malaria, Plasmodium falciparum, RIFINs form the largest erythrocyte surface protein family1. Some RIFINs can bind inhibitory immune receptors, acting as targets for unusual antibodies containing a LAIR1 ectodomain2-4, or as ligands for LILRB15. RIFINs stimulate LILRB1 activation and signalling5, thereby potentially dampening human immune responses. To understand this process, we determined a structure of a RIFIN bound to LILRB1. We show that the RIFIN mimics the natural activating ligand of LILRB1, MHC class I, in its LILRB1-binding mode. A single RIFIN mutation disrupts the complex, blocks LILRB1 binding by all tested RIFINs and abolishes signalling in a reporter assay. In a supported lipid bilayer system, which mimics NK cell activation by antibody-dependent cell-mediated cytotoxicity, both RIFIN and MHC are recruited to the NK cell immunological synapse and reduce cell activation, as measured by perforin mobilisation. Therefore, LILRB1-binding RIFINs mimic the binding mode of the natural ligand of LILRB1 and suppress NK cell function.
PMID: 32650338
ISSN: 1476-4687
CID: 4517482
Supramolecular attack particles are autonomous killing entities released from cytotoxic T cells
Cytotoxic T lymphocytes (CTLs) kill infected and cancerous cells. We detected transfer of cytotoxic multiprotein complexes, called supramolecular attack particles (SMAPs), from CTLs to target cells. SMAPs were rapidly released from CTLs and were autonomously cytotoxic. Mass spectrometry, immunochemical analysis, and CRISPR editing identified a carboxyl-terminal fragment of thrombospondin-1 as an unexpected SMAP component that contributed to target killing. Direct stochastic optical reconstruction microscopy resolved a cytotoxic core surrounded by a thrombospondin-1 shell of ~120 nanometer diameter. Cryo-soft x-ray tomography analysis revealed that SMAPs had a carbon-dense shell and were stored in multicore granules. We propose that SMAPs are autonomous extracellular killing entities that deliver cytotoxic cargo targeted by the specificity of shell components.
PMID: 32381591
ISSN: 1095-9203
CID: 4481832
Cytoskeletal tension actively sustains the migratory T-cell synaptic contact
When migratory T cells encounter antigen-presenting cells (APCs), they arrest and form radially symmetric, stable intercellular junctions termed immunological synapses which facilitate exchange of crucial biochemical information and are critical for T-cell immunity. While the cellular processes underlying synapse formation have been well characterized, those that maintain the symmetry, and thereby the stability of the synapse, remain unknown. Here we identify an antigen-triggered mechanism that actively promotes T-cell synapse symmetry by generating cytoskeletal tension in the plane of the synapse through focal nucleation of actin via Wiskott-Aldrich syndrome protein (WASP), and contraction of the resultant actin filaments by myosin II. Following T-cell activation, WASP is degraded, leading to cytoskeletal unraveling and tension decay, which result in synapse breaking. Thus, our study identifies and characterizes a mechanical program within otherwise highly motile T cells that sustains the symmetry and stability of the T cell-APC synaptic contact.
PMCID:7049817
PMID: 31894880
ISSN: 1460-2075
CID: 4481472
A checkpoint cliffhanger at the dawn of placental mammals
The PD-1 ligands PD-L1 and PD-L2 are commonly expressed on the surface of cells, where they regulate immune system activation. However, the specific role played by each ligand has been unclear. Using site-directed mutagenesis, surface plasmon resonance, and crystallography, Philips et al. explore the distinct features of PD-L2 and identify a specific evolutionary event linked to its appearance. This work provides a deeper understanding of how the immune system adapted to mammalian placental gestation and could be an important consideration in the development of new immune checkpoint therapies.
PMCID:7135975
PMID: 32245902
ISSN: 1083-351x
CID: 4376952
Single-cell glycolytic activity regulates membrane tension and HIV-1 fusion
There has been resurgence in determining the role of host metabolism in viral infection yet deciphering how the metabolic state of single cells affects viral entry and fusion remains unknown. Here, we have developed a novel assay multiplexing genetically-encoded biosensors with single virus tracking (SVT) to evaluate the influence of global metabolic processes on the success rate of virus entry in single cells. We found that cells with a lower ATP:ADP ratio prior to virus addition were less permissive to virus fusion and infection. These results indicated a relationship between host metabolic state and the likelihood for virus-cell fusion to occur. SVT revealed that HIV-1 virions were arrested at hemifusion in glycolytically-inactive cells. Interestingly, cells acutely treated with glycolysis inhibitor 2-deoxyglucose (2-DG) become resistant to virus infection and also display less surface membrane cholesterol. Addition of cholesterol in these in glycolytically-inactive cells rescued the virus entry block at hemifusion and enabled completion of HIV-1 fusion. Further investigation with FRET-based membrane tension and membrane order reporters revealed a link between host cell glycolytic activity and host membrane order and tension. Indeed, cells treated with 2-DG possessed lower plasma membrane lipid order and higher tension values, respectively. Our novel imaging approach that combines lifetime imaging (FLIM) and SVT revealed not only changes in plasma membrane tension at the point of viral fusion, but also that HIV is less likely to enter cells at areas of higher membrane tension. We therefore have identified a connection between host cell glycolytic activity and membrane tension that influences HIV-1 fusion in real-time at the single-virus fusion level in live cells.
PMID: 32084246
ISSN: 1553-7374
CID: 4312762
Author Correction: Human in vitro-induced regulatory T cells display Dlgh1 dependent and PKC-θ restrained suppressive activity
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
PMID: 32076101
ISSN: 2045-2322
CID: 4312432
Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)
These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.
PMID: 31633216
ISSN: 1521-4141
CID: 4146932
A tissue-like platform for studying engineered quiescent human T-cells' interactions with dendritic cells
Research in the field of human immunology is restricted by the lack of a system that reconstitutes the in-situ activation dynamics of quiescent human antigen-specific T-cells interacting with dendritic cells. Here we report a tissue-like system that recapitulates the dynamics of engineered primary human immune cell. Our approach facilitates real-time single cell manipulations, tracking of interactions and functional responses complemented by population-based measurements of cytokines, activation status and proliferation. As a proof of concept, we recapitulate immunological phenomenon such as CD4 help to CD8 T-cells through enhanced maturation of DCs and effect of PD-1 checkpoint blockades. In addition, we characterise unique dynamics of T-cell/DC interactions as a function of antigen affinity.
PMID: 31552826
ISSN: 2050-084x
CID: 4107672
An X-ray Vision for Phosphoantigen Recognition [Comment]
Invariant Vγ9Vδ2 T cells respond to "phosphoantigen" metabolites through binding to the B30.2 domain of butyrophilin BTN3A. Yang et al. (2019) use molecular dynamic simulations based on X-ray structures of distinct B30.2 domain dimers to identify the asymmetric dimer as most active, which has implications for the inside-out signaling mechanism.
PMID: 30995494
ISSN: 1097-4180
CID: 4096142
Integrins and Their Role in Immune Cell Adhesion
One of the 2019 Canada Gairdner International Awards recognizes Timothy Springer's discovery of the first immune system adhesion molecules involved in lymphocyte homing and the translation of those discoveries into therapeutics for autoimmune disease and cancer.
PMID: 30952447
ISSN: 1097-4172
CID: 4095272
