21 research outputs found
Immune mobilising T cell receptors redirect polyclonal CD8+ T cells in chronic HIV infection to form immunological synapses
T cell exhaustion develops in human immunodeficiency virus (HIV) infection due to chronic viral antigenic stimulation. This adaptive response primarily affects virus-specific CD8+ T cells, which may remain dysfunctional despite viral load-reducing antiretroviral therapy; however, abnormalities may also be evident in non-HIV-specific populations. Both could limit the efficacy of cell therapies against viral reservoirs. Here, we show that bulk (polyclonal) CD8+ T cells from people living with HIV (PLWH) express proposed markers of dysfunctional HIV-specific T cells at high levels yet form lytic immunological synapses (IS) and eliminate primary resting infected (HIV Gaglo) CD4+ T cells, when redirected by potent bispecific T cell-retargeting molecules, Immune mobilising monoclonal T cell receptors (TCR) Against Virus (ImmTAV). While PLWH CD8+ T cells are functionally impaired when compared to CD8+ T cells from HIV-naĂŻve donors, ImmTAV redirection enables them to eliminate Gaglo CD4+ T cells that are insensitive to autologous HIV-specific cytolytic T cells. ImmTAV molecules may therefore be able to target HIV reservoirs, which represent a major barrier to a cure
CCR8 Expression Defines Tissue-Resident Memory T Cells in Human Skin
Human skin harbors two major T cell compartments of equal size that are distinguished by expression of the chemokine receptor CCR8. In vitro studies have demonstrated that CCR8 expression is regulated by TCR engagement and the skin tissue microenvironment. To extend these observations, we examined the relationship between CCR8+ and CCR8â skin T cells in vivo. Phenotypic, functional, and transcriptomic analyses revealed that CCR8+ skin T cells bear all the hallmarks of resident memory T cells, including homeostatic proliferation in response to IL-7 and IL-15, surface expression of tissue localization (CD103) and retention (CD69) markers, low levels of inhibitory receptors (programmed cell death protein 1, Tim-3, LAG-3), and a lack of senescence markers (CD57, killer cell lectin-like receptor subfamily G member 1). In contrast, CCR8â skin T cells are heterogeneous and comprise variable numbers of exhausted (programmed cell death protein 1+), senescent (CD57+, killer cell lectin-like receptor subfamily G member 1+), and effector (T-bethi, Eomeshi) T cells. Importantly, conventional and high-throughput sequencing of expressed TCR ÎČ-chain (TRB) gene rearrangements showed that these CCR8-defined populations are clonotypically distinct, suggesting unique ontogenies in response to separate antigenic challenges and/or stimulatory conditions. Moreover, CCR8+ and CCR8â skin T cells were phenotypically stable in vitro and displayed similar levels of telomere erosion, further supporting the likelihood of a nonlinear differentiation pathway. On the basis of these results, we propose that long-lived memory T cells in human skin can be defined by the expression of CCR8
Skin metabolites define a new paradigm in the localization of skin tropic memory T cells
The localization of memory T cells to human skin is essential for long-term immune surveillance and the maintenance of barrier integrity. The expression of CCR8 during naive T cell activation is controlled by skin-specific factors derived from epidermal keratinocytes and not by resident dendritic cells. In this study, we show that the CCR8-inducing factors are heat stable and protease resistant and include the vitamin D3 metabolite 1α,25-dihydroxyvitamin D3 and PGE2. The effect of either metabolite alone on CCR8 expression was weak, whereas their combination resulted in robust CCR8 expression. Elevation of intracellular cAMP was essential because PGE2 could be substituted with the adenylyl cyclase agonist forskolin, and CCR8 expression was sensitive to protein kinase A inhibition. For effective induction, exposure of naive T cells to these epidermal factors needed to occur either prior to or during T cell activation even though CCR8 was only detected 4â5 d later in proliferating T cells. The importance of tissue environments in maintaining cellular immune surveillance networks within distinct healthy tissues provides a paradigm shift in adaptive immunity. Epidermal-derived vitamin D3 metabolites and PGs provide an essential cue for the localization of CCR8+ immune surveillance T cells within healthy human skin
Epithelial chemokine CXCL14 synergizes with CXCL12 via allosteric modulation of CXCR4
The chemokine receptor, CXC chemokine receptor 4 (CXCR4), is selective for CXC chemokine ligand 12 (CXCL12), is broadly expressed in blood and tissue cells, and is essential during embryogenesis and hematopoiesis. CXCL14 is a homeostatic chemokine with unknown receptor selectivity and preferential expression in peripheral tissues. Here, we demonstrate that CXCL14 synergized with CXCL12 in the induction of chemokine responses in primary human lymphoid cells and cell lines that express CXCR4. Combining subactive concentrations of CXCL12 with 100â300 nM CXCL14 resulted in chemotaxis responses that exceeded maximal responses that were obtained with CXCL12 alone. CXCL14 did not activate CXCR4-expressing cells (i.e., failed to trigger chemotaxis and Ca2+ mobilization, as well as signaling via ERK1/2 and the small GTPase Rac1); however, CXCL14 bound to CXCR4 with high affinity, induced redistribution of cell-surface CXCR4, and enhanced HIV-1 infection by >3-fold. We postulate that CXCL14 is a positive allosteric modulator of CXCR4 that enhances the potency of CXCR4 ligands. Our findings provide new insights that will inform the development of novel therapeutics that target CXCR4 in a range of diseases, including cancer, autoimmunity, and HIV.âCollins, P. J., McCully, M. L., MartŽınez-Muñoz, L., Santiago, C.,Wheeldon, J., Caucheteux, S., Thelen, S., Cecchinato, V., Laufer, J.M., Purvanov, V.,Monneau, Y. R., Lortat-Jacob, H., Legler, D. F., Uguccioni, M., Thelen, M., Piguet, V., Mellado, M., Moser, B. Epithelial chemokine CXCL14 synergizes with CXCL12 via allosteric modulation of CXCR4. FASEB J. 31, 000â000 (2017). www.fasebj.or
Epidermis instructs skin homing receptor expression in human T cells
The localization of memory T cells to human skin is essential for long-term immune surveillance and the maintenance of barrier integrity. Although the mechanisms controlling memory T-cell migration to peripheral tissues are poorly understood, the current paradigm includes the localized secretion of âimprintingâ signals from tissue-resident dendritic cells in the draining lymph nodes. Here we show that CCR8 expression by newly activated naive T cells is regulated by skin-specific factor(s) derived primarily from epidermal keratinocytes, thereby providing a mechanism for the preferential expression of CCR8 by skin-resident memory T cells. Importantly, no such effects were observed after coculture with primary cells from skin-unrelated epithelia, including mesothelium and small intestine. The keratinocyte-derived CCR8-inducing factor(s) were soluble, and independent of vitamins A and D. Furthermore, the induction of CCR8 under these conditions correlated with an increase in cutaneous lymphocyte-associated antigen expression. Our findings challenge current tissue homing paradigms, especially those involving CCR10, and emphasize the importance of steady-state epidermis rather than tissue-resident dendritic cells in controlling the localization of memory T cells within human skin
Skin Metabolites Define a New Paradigm in the Localization of Skin Tropic Memory T Cells
The localization of memory T cells to human skin is essential for long-term immune surveillance and the maintenance of barrier integrity. The expression of CCR8 during naive T cell activation is controlled by skin-specific factors derived from epidermal keratinocytes and not by resident dendritic cells. In this study, we show that the CCR8-inducing factors are heat stable and protease resistant and include the vitamin D3 metabolite 1α,25-dihydroxyvitamin D3 and PGE2. The effect of either metabolite alone on CCR8 expression was weak, whereas their combination resulted in robust CCR8 expression. Elevation of intracellular cAMP was essential because PGE2 could be substituted with the adenylyl cyclase agonist forskolin, and CCR8 expression was sensitive to protein kinase A inhibition. For effective induction, exposure of naive T cells to these epidermal factors needed to occur either prior to or during T cell activation even though CCR8 was only detected 4â5 d later in proliferating T cells. The importance of tissue environments in maintaining cellular immune surveillance networks within distinct healthy tissues provides a paradigm shift in adaptive immunity. Epidermal-derived vitamin D3 metabolites and PGs provide an essential cue for the localization of CCR8+ immune surveillance T cells within healthy human skin
Epidermis instructs skin homing receptor expression in human T cells
The localization of memory T cells to human skin is essential for long-term immune surveillance and the maintenance of barrier integrity. Although the mechanisms controlling memory T-cell migration to peripheral tissues are poorly understood, the current paradigm includes the localized secretion of âimprintingâ signals from tissue-resident dendritic cells in the draining lymph nodes. Here we show that CCR8 expression by newly activated naive T cells is regulated by skin-specific factor(s) derived primarily from epidermal keratinocytes, thereby providing a mechanism for the preferential expression of CCR8 by skin-resident memory T cells. Importantly, no such effects were observed after coculture with primary cells from skin-unrelated epithelia, including mesothelium and small intestine. The keratinocyte-derived CCR8-inducing factor(s) were soluble, and independent of vitamins A and D. Furthermore, the induction of CCR8 under these conditions correlated with an increase in cutaneous lymphocyte-associated antigen expression. Our findings challenge current tissue homing paradigms, especially those involving CCR10, and emphasize the importance of steady-state epidermis rather than tissue-resident dendritic cells in controlling the localization of memory T cells within human skin
Structural and Functional Consequences of the Cardiac Troponin C L48Q Ca<sup>2+</sup>-Sensitizing Mutation
Calcium binding to the regulatory domain of cardiac troponin
C
(cNTnC) causes a conformational change that exposes a hydrophobic
surface to which troponin I (cTnI) binds, prompting a series of proteinâprotein
interactions that culminate in muscle contraction. A number of cTnC
variants that alter the Ca<sup>2+</sup> sensitivity of the thin filament
have been linked to disease. Tikunova and Davis engineered a series
of cNTnC mutations that altered Ca<sup>2+</sup> binding properties
and studied the effects on the Ca<sup>2+</sup> sensitivity of the
thin filament and contraction [Tikunova, S. B., and Davis, J. P. (2004) <i>J. Biol. Chem. 279</i>, 35341â35352]. One of the mutations
they engineered, the L48Q variant, resulted in a pronounced increase
in the cNTnC Ca<sup>2+</sup> binding affinity and Ca<sup>2+</sup> sensitivity
of cardiac muscle force development. In this work, we sought structural
and mechanistic explanations for the increased Ca<sup>2+</sup> sensitivity
of contraction for the L48Q cNTnC variant, using an array of biophysical
techniques. We found that the L48Q mutation enhanced binding of both
Ca<sup>2+</sup> and cTnI to cTnC. Nuclear magnetic resonance chemical
shift and relaxation data provided evidence that the cNTnC hydrophobic
core is more exposed with the L48Q variant. Molecular dynamics simulations
suggest that the mutation disrupts a network of crucial hydrophobic
interactions so that the closed form of cNTnC is destabilized. The
findings emphasize the importance of cNTnCâs conformation in
the regulation of contraction and suggest that mutations in cNTnC
that alter myofilament Ca<sup>2+</sup> sensitivity can do so by modulating
Ca<sup>2+</sup> and cTnI binding