The adaptor protein SAP regulates type II NKT-cell development, cytokine production, and cytotoxicity against lymphoma

Genome Editing With TALEN, CRISPR-Cas9 and CRISPR-Cas12a in Combination With AAV6 Homology Donor Restores T Cell Function for XLP

X-linked lymphoproliferative disease is a rare inherited immune disorder, caused by mutations or deletions in the SH2D1A gene that encodes an intracellular adapter protein SAP (Slam-associated protein). SAP is essential for mediating several key immune processes and the immune system - T cells in particular - are dysregulated in its absence. Patients present with a spectrum of clinical manifestations, including haemophagocytic lymphohistiocytosis (HLH), dysgammaglobulinemia, lymphoma and autoimmunity. Treatment options are limited, and patients rarely survive to adulthood without an allogeneic haematopoietic stem cell transplant (HSCT). However, this procedure can have poor outcomes in the mismatched donor setting or in the presence of active HLH, leaving an unmet clinical need. Autologous haematopoeitic stem cell or T cell therapy may offer alternative treatment options, removing the need to find a suitable donor for HSCT and any risk of alloreactivity. SAP has a tightly controlled expression profile that a conventional lentiviral gene delivery platform may not be able to fully replicate. A gene editing approach could preserve more of the endogenous regulatory elements that govern SAP expression, potentially providing a more optimum therapy. Here, we assessed the ability of TALEN, CRISPR-Cas9 and CRISPR-Cas12a nucleases to drive targeted insertion of SAP cDNA at the first exon of the SH2D1A locus using an adeno-associated virus serotype 6 (AAV6)-based vector containing the donor template. All nuclease platforms were capable of high efficiency gene editing, which was optimised using a serum-free AAV6 transduction protocol. We show that T cells from XLP patients corrected by gene editing tools have restored physiological levels of SAP gene expression and restore SAP-dependent immune functions, indicating a new therapeutic opportunity for XLP patients.

Ceramide Synthase 2 Null Mice Are Protected from Ovalbumin-Induced Asthma with Higher T Cell Receptor Signal Strength in CD4+ T Cells

(1) Background: six mammalian ceramide synthases (CerS1–6) determine the acyl chain length of sphingolipids (SLs). Although ceramide levels are increased in murine allergic asthma models and in asthmatic patients, the precise role of SLs with specific chain lengths is still unclear. The role of CerS2, which mainly synthesizes C22–C24 ceramides, was investigated in immune responses elicited by airway inflammation using CerS2 null mice. (2) Methods: asthma was induced in wild type (WT) and CerS2 null mice with ovalbumin (OVA), and inflammatory cytokines and CD4 (cluster of differentiation 4)+ T helper (Th) cell profiles were analyzed. We also compared the functional capacity of CD4+ T cells isolated from WT and CerS2 null mice. (3) Results: CerS2 null mice exhibited milder symptoms and lower Th2 responses than WT mice after OVA exposure. CerS2 null CD4+ T cells showed impaired Th2 and increased Th17 responses with concomitant higher T cell receptor (TCR) signal strength after TCR stimulation. Notably, increased Th17 responses of CerS2 null CD4+ T cells appeared only in TCR-mediated, but not in TCR-independent, treatment. (4) Conclusions: altered Th2/Th17 immune response with higher TCR signal strength was observed in CerS2 null CD4+ T cells upon TCR stimulation. CerS2 and very-long chain SLs may be therapeutic targets for Th2-related diseases such as asthma.

Targeting mitochondrial dysfunction in MAIT cells: Potential immunotherapeutic treatment for colorectal cancer

Mucosal associated invariant T (MAIT) cells have captured the attention of immunologists and clinicians in recent years due to their abundance in humans, especially in human liver and mucosal tissue. Colorectal cancer is one of the most common forms of cancer in mucosal tissue. Recent evidence reveal activated MAIT cells within the microenvironment of colorectal tumors. The increased tumor infiltration with MAIT cells correlates with poor survival in the colorectal cancer patients, suggesting MAIT cells are promising immunotherapeutic targets in colorectal cancer. Besides well-known role in anti-microbial immunity, MAIT cells have been associated with various forms of cancer. The Th1-biased MAIT cells are proposed to mediate anti-tumor immunity, while IL-17-producing subsets have been implicated in promoting malignancy. Reduced IFN-γ production and elevated IL-17 production of MAIT cells have been found in colorectal tumor tissue and shown to promote tumor growth and metastases. Although the mechanism(s) driving the increase in Th17-biased MAIT cells with reduced IFN-γ production in tumor is not fully understood, recent studies have linked IL-17 response to dysfunctional mitochondria and reactive oxygen species (ROS) from the mitochondria. Therefore, we hypothesize that mitochondrial dysfunction contributes to Th17-skewed MAIT cell responses with decreased IFN-γ production. Mitochondrial targeted antioxidants are supposed to be beneficial for recovering Th1-baised antitumor immunity and inhibiting IL-17 production of MAIT by improving mitochondrial function.

Mechanisms of Antiphospholipid Syndrome Induction: Role of NKT Cells

The review discusses the mechanisms of participation of natural killer T cells (NKT cells) in the induction of antiphospholipid antibodies (APA) that play a major pathogenetic role in the formation of antiphospholipid syndrome (APS), summarizes the data on APS pathogenesis, and presents modern concepts on the antibody formation involving follicular helper type II NK cells.

SLAM-SAP-Fyn: Old Players with New Roles in iNKT Cell Development and Function

Invariant natural killer T (iNKT) cells are a unique T cell lineage that develop in the thymus and emerge with a memory-like phenotype. Accordingly, following antigenic stimulation, they can rapidly produce copious amounts of Th1 and Th2 cytokines and mediate activation of several immune cells. Thus, it is not surprising that iNKT cells play diverse roles in a broad range of diseases. Given their pivotal roles in host immunity, it is crucial that we understand the mechanisms that govern iNKT cell development and effector functions. Over the last two decades, several studies have contributed to the current knowledge of iNKT cell biology and activity. Collectively, these studies reveal that the thymic development of iNKT cells, their lineage expansion, and functional properties are tightly regulated by a complex network of transcription factors and signaling molecules. While prior studies have clearly established the importance of the SLAM-SAP-Fyn signaling axis in iNKT cell ontogenesis, recent studies provide exciting mechanistic insights into the role of this signaling cascade in iNKT cell development, lineage fate decisions, and functions. Here we summarize the previous literature and discuss the more recent studies that guide our understanding of iNKT cell development and functional responses.

Defining a novel subset of CD1d-dependent type II natural killer T cells using natural killer cell-associated markers

Natural killer T (NKT) cells are αβ T cell receptor (TCR) expressing innate‐like T cells that display natural killer (NK) cell markers. Based on TCR characteristics, they are divided into two groups restricted to the MHC class I‐like molecule CD1d. Type I NKT cells, most extensively studied, are identified by a semi‐invariant Vα14‐Jα18 (mouse, Vα24‐Jα18 in humans) TCR reactive to the prototypic ligand α‐galactosylceramide presented on CD1d. In contrast, type II NKT cells display diverse TCR reacting to different CD1d‐presented ligands. There are no reagents that identify all type II NKT cells, limiting their exploration. Here, we searched for novel type II NKT cells by comparing Jα18^−/−MHCII^−/− mice that harbour type II but not type I NKT cells, and CD1d^−/−MHCII^−/− mice, lacking all NKT cells. We identified significantly larger populations of CD4⁺ and CD4⁻CD8⁻ (double negative, DN) TCRβ⁺ cells expressing NKG2D or NKG2A/C/E in Jα18^−/−MHCII^−/− mice compared with CD1d^−/−MHCII^−/− mice, suggesting that 30%‐50% of these cells were type II NKT cells. They expressed CD122, NK1.1, CXCR3 and intermediate/low levels of CD45RB. Further, the CD4⁺ subset was CD69⁺, while the DN cells were CD49b⁺ and CD62L⁺. Both subsets expressed the NKT cell‐associated promyelocytic leukaemia zinc finger (PLZF) transcription factor and Tbet, while fewer cells expressed RORγt. NKG2D⁺ CD4⁺ and DN populations were producers of IFN‐γ, but rarely IL‐4 and IL‐17. Taken together, we identify a novel subset of primary CD4⁺ and DN type II NKT cells that expresses NKG2 receptors have typical NKT cell phenotypes and a TH1‐like cytokine production.

The Dynamics of the Skin's Immune System

The skin is a complex organ that has devised numerous strategies, such as physical, chemical, and microbiological barriers, to protect the host from external insults. In addition, the skin contains an intricate network of immune cells resident to the tissue, crucial for host defense as well as tissue homeostasis. In the event of an insult, the skin-resident immune cells are crucial not only for prevention of infection but also for tissue reconstruction. Deregulation of immune responses often leads to impaired healing and poor tissue restoration and function. In this review, we will discuss the defensive components of the skin and focus on the function of skin-resident immune cells in homeostasis and their role in wound healing.

Lipid-Reactive T Cells in Immunological Disorders of the Lung

Regulation of T cell-mediated immunity in the lungs is critical for prevention of immune-related lung disorders and for host protection from pathogens. While the prevalent view of pulmonary T cell responses is based on peptide recognition by antigen receptors, called T cell receptors (TCR), on the T cell surface in the context of classical major histocompatibility complex (MHC) molecules, novel pathways involving the presentation of lipid antigens by cluster of differentiation 1 (CD1) molecules to lipid-reactive T cells are emerging as key players in pulmonary immune system. Whereas, genetic conservation of group II CD1 (CD1d) in mouse and human genomes facilitated numerous in vivo studies of CD1d-restricted invariant natural killer T (iNKT) cells in lung diseases, the recent development of human CD1-transgenic mice has made it possible to examine the physiological roles of group I CD1 (CD1a-c) molecules in lung immunity. Here, we discuss current understanding of the biology of CD1-reactive T cells with a specific focus on their roles in several pulmonary disorders.

Primary immunodeficiencies associated with EBV-Induced lymphoproliferative disorders

Primary immunodeficiency diseases (PIDs) are a subgroup of inherited immunological disorders that increase susceptibility to viral infections. Among the range of viral pathogens involved, EBV remains a major threat because of its high prevalence of infection among the adult population and its tendency to progress to life-threatening lymphoproliferative disorders (LPDs) and/or malignancy. The high mortality in immunodeficient patients with EBV-driven LPDs, despite institution of diverse and often intensive treatments, prompts the need to better study these PIDs to identify and understand the affected molecular pathways that increase susceptibility to EBV infection and progression. In this article, we have provided a detailed literature review of the reported cases of EBV-driven LPDs in patients with PID. We discuss the PIDs associated with development of EBV-LPDs. Then, we review the nature and the therapeutic outcome of common EBV- driven LPDs in the PID patients and review the mechanisms common to the major PIDs. Deep study of these common pathways and gaining a better insight into the disease nature and outcomes, may lead to earlier diagnosis of the disease, choosing the best treatment modalities available and development of novel therapeutic strategies to decrease morbidity and mortality brought about by EBV infection.

The Extended Family of CD1d-Restricted NKT Cells: Sifting through a Mixed Bag of TCRs, Antigens, and Functions

Natural killer T (NKT) cells comprise a family of specialized T cells that recognize lipid antigens presented by CD1d. Based on their T cell receptor (TCR) usage and antigen specificities, CD1d-restricted NKT cells have been divided into two main subsets: type I NKT cells that use a canonical invariant TCR α-chain and recognize α-galactosylceramide (α-GalCer), and type II NKT cells that use a more diverse αβ TCR repertoire and do not recognize α-GalCer. In addition, α-GalCer-reactive NKT cells that use non-canonical αβ TCRs and CD1d-restricted T cells that use γδ or δ/αβ TCRs have recently been identified, revealing further diversity among CD1d-restricted T cells. Importantly, in addition to their distinct antigen specificities, functional differences are beginning to emerge between the different members of the CD1d-restricted T cell family. In this review, while using type I NKT cells as comparison, we will focus on type II NKT cells and the other non-invariant CD1d-restricted T cell subsets, and discuss our current understanding of the antigens they recognize, the formation of stimulatory CD1d/antigen complexes, the modes of TCR-mediated antigen recognition, and the mechanisms and consequences of their activation that underlie their function in antimicrobial responses, anti-tumor immunity, and autoimmunity.

Role of Group 1 CD1-Restricted T Cells in Infectious Disease

The evolutionarily conserved CD1 family of antigen-presenting molecules presents lipid antigens rather than peptide antigens to T cells. CD1 molecules, unlike classical MHC molecules, display limited polymorphism, making CD1-restricted lipid antigens attractive vaccine targets that could be recognized in a genetically diverse human population. Group 1 CD1 (CD1a, CD1b, and CD1c)-restricted T cells have been implicated to play critical roles in a variety of autoimmune and infectious diseases. In this review, we summarize current knowledge and recent discoveries on the development of group 1 CD1-restricted T cells and their function in different infection models. In particular, we focus on (1) newly identified microbial and self-lipid antigens, (2) kinetics, phenotype, and unique properties of group 1 CD1-restricted T cells during infection, and (3) the similarities of group 1 CD1-restricted T cells to the closely related group 2 CD1-restricted T cells.