Project description:We examined the relationship between peripheral blood levels of SARS-CoV-2 S (Spike protein)1/M (Membrane protein)-reactive IFN-γ-producing CD4+ and CD8+ T cells, serum levels of biomarkers of clinical severity, and mortality in critically ill COVID-19 patients. The potential association between SARS-CoV-2-S-Receptor Binding Domain (RBD)-specific IgG levels in sera and mortality was also investigated. SARS-CoV-2 T cells and anti-RBD IgG levels were monitored in 71 non-consecutive patients (49 male and 22 female; median age, 65 years) by whole-blood flow cytometry and Enzyme-linked immunosorbent assay (ELISA), respectively (326 specimens). SARS-CoV-2 RNA loads in paired tracheal aspirates [TA] (n = 147) were available from 54 patients. Serum levels of interleukin-6, ferritin, D-Dimer, lactose dehydrogenase and C-reactive protein in paired sera were known. SARS-CoV-2 T cells (either CD4+, CD8+ or both) were detectable in 70 patients. SARS-CoV-2 IFN-γ CD4+ T-cell responses were documented more frequently than their CD8+ counterparts (62 vs. 56 patients) and were of greater magnitude overall. Detectable SARS-CoV-2 S1/M-reactive CD8+ and CD4+ T-cell responses were associated with higher SARS-CoV-2 RNA loads in TA. SARS-CoV-2 RNA load in TA decreased over time, irrespective of the dynamics of SARS-CoV-2-reactive CD8+ and CD4+ T cells. No correlation was found between SARS-CoV-2 IFN-γ T-cell counts, anti-RBD IgG concentrations and biomarker serum levels (Rho ≤ 0.3). The kinetics of both T cell subsets was comparable between those who died or survived, whereas anti-RBD IgG levels were higher across different time points in deceased patients than in survivors. Enumeration of peripheral blood levels of SARS-CoV-2-S1/M-reactive IFN-γ CD4+ and CD8+ T cells does not predict viral clearance from the lower respiratory tract or poor clinical outcomes in critically ill COVID-19 patients. In contrast, anti-RBD IgG levels were directly associated with increased mortality.
Project description:Type 1 diabetes (T1D) results from T cell-mediated destruction of insulin-producing β-cells. Insulin represents a key self-antigen in disease pathogenesis, as recent studies identified proinsulin-responding T cells from inflamed pancreatic islets of organ donors with recent-onset T1D. These cells respond to an insulin B-chain (InsB) epitope presented by the HLA-DQ8 molecule associated with high T1D risk. Understanding insulin-specific T-cell frequency and phenotype in peripheral blood is now critical. We constructed fluorescent InsB10-23:DQ8 tetramers, stained peripheral blood lymphocytes directly ex vivo, and show DQ8+ patients with T1D have increased tetramer+ CD4+ T cells compared with HLA-matched control subjects without diabetes. Patients with a shorter disease duration had higher frequencies of insulin-reactive CD4+ T cells, with most of these cells being antigen experienced. We also demonstrate that the number of insulin tetramer+ effector memory cells is directly correlated with insulin antibody titers, suggesting insulin-specific T- and B-cell interactions. Notably, one of four control subjects with tetramer+ cells was a first-degree relative who had insulin-specific cells with an effector memory phenotype, potentially representing an early marker of T-cell autoimmunity. Our results suggest that studying InsB10-23:DQ8 reactive T-cell frequency and phenotype may provide a biomarker of disease activity in patients with T1D and those at risk.
Project description:We recently demonstrated that the major effector function of neonatal CD4+ T cells is to produce CXCL8, a prototypic cytokine of innate immune cells. In this article, we show that CXCL8 expression, prior to proliferation, is common in newly arising T cells (so-called "recent thymic emigrants") in adults, as well as in babies. This effector potential is acquired in the human thymus, prior to TCR signaling, but rather than describing end-stage differentiation, such cells, whether isolated from neonates or adults, can further differentiate into IFN-γ-producing CD4+ T cells. Thus, the temporal transition of host defense from innate to adaptive immunity is unexpectedly mirrored at the cellular level by the capacity of human innate-like CXCL8-producing CD4+ T cells to transition directly into Th1 cells.
Project description:Dendritic cells (DCs) play a key role in the initiation of an immune response and are known as "professional" APCs because of their ability to activate naive T cells. A widely used method to generate DCs in vitro is to culture bone marrow (BM) cells or blood monocytes in the presence of GM-CSF and IL-4. In this study, we show that a small population of NK cells residing in the BM of RAG-/-, but not RAG-/- γc chain-/- mice, remain in the DC culture and is the source of IFN-γ produced after stimulation with LPS. These cells, which may represent early promoters of LPS-induced responses, have to be taken into account when interpreting experiments using BM-derived DCs.
Project description:Poxvirus infections of the skin are a recent emerging public health concern, yet the mechanisms that mediate protective immunity against these viral infections remain largely unknown. Here, we show that T helper 1 (Th1) memory CD4+ T cells are necessary and sufficient to provide complete and broad protection against poxvirus skin infections, whereas memory CD8+ T cells are dispensable. Core 2 O-glycan-synthesizing Th1 effector memory CD4+ T cells rapidly infiltrate the poxvirus-infected skin microenvironment and produce interferon γ (IFNγ) in an antigen-dependent manner, causing global changes in gene expression to promote anti-viral immunity. Keratinocytes express IFN-stimulated genes, upregulate both major histocompatibility complex (MHC) class I and MHC class II antigen presentation in an IFNγ-dependent manner, and require IFNγ receptor (IFNγR) signaling and MHC class II expression for memory CD4+ T cells to protect the skin from poxvirus infection. Thus, Th1 effector memory CD4+ T cells exhibit potent anti-viral activity within the skin, and keratinocytes are the key targets of IFNγ necessary for preventing poxvirus infection of the epidermis.
Project description:Memory formation is a hallmark of T cell-mediated immunity, but how differentiation into either short-lived effector cells (SLECs, CD127-KLRG1+) or memory precursors cells (MPECs, CD127+KLRG1-) and subsequent regulation of long-term memory is adjusted is incompletely understood. Here, we show that loss of the nuclear orphan receptor NR2F6 in germ-line Nr2f6-deficient mice enhances antigen-specific CD8+ memory formation up to 70 days after bacterial infection with Listeria monocytogenes (LmOVA) and boosts inflammatory IFN-γ, TNFα, and IL-2 cytokine recall responses. Adoptive transfer experiments using Nr2f6-/- OT-I T-cells showed that the augmented memory formation is CD8+ T-cell intrinsic. Although the relative difference between the Nr2f6+/+ and Nr2f6-/- OT-I memory compartment declines over time, Nr2f6-deficient OT-I memory T cells mount significantly enhanced IFN-γ responses upon reinfection with increased clonal expansion and improved host antigen-specific CD8+ T-cell responses. Following a secondary adoptive transfer into naïve congenic mice, Nr2f6-deficient OT-I memory T cells are superior in clearing LmOVA infection. Finally, we show that the commitment to enhanced memory within Nr2f6-deficient OT-I T cells is established in the early phases of the antibacterial immune response and is IFN-γ mediated. IFN-γ blocking normalized MPEC formation of Nr2f6-deficient OT-I T cells. Thus, deletion or pharmacological inhibition of NR2F6 in antigen-specific CD8+ T cells may have therapeutic potential for enhancing early IFN-γ production and consequently the functionality of memory CD8+ T cells in vivo.
Project description:Dendritic cells (DC) initiate the differentiation of CD4+ helper T cells into effector cells including Th1 and Th17 responses that play an important role in inflammation and autoimmune disease pathogenesis. In mice, Th1 and Th17 responses are regulated by different conventional (c) DC subsets, with cDC1 being the main producers of IL-12p70 and inducers of Th1 responses, while cDC2 produce IL-23 to promote Th17 responses. The role that human DC subsets play in memory CD4+ T cell activation is not known. This study investigated production of Th1 promoting cytokine IL-12p70, and Th17 promoting cytokines, IL-1β, IL-6, and IL-23, by human blood monocytes, CD1c+ DC, CD141+ DC, and plasmacytoid DC and examined their ability to induce Th1 and Th17 responses in memory CD4+ T cells. Human CD1c+ DC produced IL-12p70, IL-1β, IL-6, and IL-23 in response to R848 combined with LPS or poly I:C. CD141+ DC were also capable of producing IL-12p70 and IL-23 but were not as proficient as CD1c+ DC. Activated CD1c+ DC were endowed with the capacity to promote both Th1 and Th17 effector function in memory CD4+ T cells, characterized by high production of interferon-γ, IL-17A, IL-17F, IL-21, and IL-22. These findings support a role for CD1c+ DC in autoimmune inflammation where Th1/Th17 responses play an important role in disease pathogenesis.
Project description:The T-cell-mediated immune response is implicated in many clinical hepatic injuries, such as autoimmune hepatitis and acute virus hepatitis. CD24 is widely expressed by different immune cells and plays an important role in the pathogenesis of many autoimmune diseases. However, the role of CD24 in T-cell-mediated liver injury has not been elucidated until now. Here we showed that CD24 deficiency protects mice from concanavalin A (ConA)-induced fulminant liver injury by reducing serum interferon-γ (IFN-γ) levels. CD24 expression by hepatic T cells was markedly increased following ConA challenge. Moreover, decreased IFN-γ production by hepatic CD4+ T cells in CD24-deficient mice was detected, which was correlated with downregulated phosphorylation of STAT1 in hepatic tissue. In vitro experiments also supported the conclusion that CD24 deficiency impaired IFN-γ production by CD4+ T cells following ConA, CD3/CD28 and phorbol myristate acetate/ionomycin stimulation. Our study suggests that CD24 deficiency confers hepatoprotection by decreasing CD4+ T-cell-dependent IFN-γ production in vivo, which suggests that CD24 might be a potential target molecule for reducing clinical hepatitis.
Project description:Although B cells play important roles in the humoral immune response and the regulation of adaptive immunity, B cell subpopulations with unique phenotypes, particularly those with non-classical immune functions, should be further investigated. By challenging mice with Listeria monocytogenes, Escherichia coli, vesicular stomatitis virus and Toll-like receptor ligands, we identified an inducible CD11a(hi)FcγRIII(hi) B cell subpopulation that is significantly expanded and produces high levels of IFN-γ during the early stage of the immune response. This subpopulation of B cells can promote macrophage activation via generating IFN-γ, thereby facilitating the innate immune response against intracellular bacterial infection. As this new subpopulation is of B cell origin and exhibits the phenotypic characteristics of B cells, we designated these cells as IFN-γ-producing innate B cells. Dendritic cells were essential for the inducible generation of these innate B cells from the follicular B cells via CD40L-CD40 ligation. Increased Bruton's tyrosine kinase activation was found to be responsible for the increased activation of non-canonical NF-κB pathway in these innate B cells after CD40 ligation, with the consequent induction of additional IFN-γ production. The identification of this new population of innate B cells may contribute to a better understanding of B cell functions in anti-infection immune responses and immune regulation.