Development of γδ T Cells, the Special-Force Soldiers of the Immune System

The Chicken Embryo Model: A Novel and Relevant Model for Immune-Based Studies

Dysregulation of the immune system is associated with many pathologies, including cardiovascular diseases, diabetes, and cancer. To date, the most commonly used models in biomedical research are rodents, and despite the various advantages they offer, their use also raises numerous drawbacks. Recently, another in vivo model, the chicken embryo and its chorioallantoic membrane, has re-emerged for various applications. This model has many benefits compared to other classical models, as it is cost-effective, time-efficient, and easier to use. In this review, we explain how the chicken embryo can be used as a model for immune-based studies, as it gradually develops an embryonic immune system, yet which is functionally similar to humans'. We mainly aim to describe the avian immune system, highlighting the differences and similarities with the human immune system, including the repertoire of lymphoid tissues, immune cells, and other key features. We also describe the general in ovo immune ontogeny. In conclusion, we expect that this review will help future studies better tailor their use of the chicken embryo model for testing specific experimental hypotheses or performing preclinical testing.

Increased Vδ1γδT cells predominantly contributed to IL-17 production in the development of adult human post-infectious irritable bowel syndrome

Background

γδT cells play an important role in the mucosa inflammation and immunity-associated disorders. Our previous study reported that γδ T cells producing IL-17 were involved in the pathogenesis of post-infectious irritable bowel syndrome (PI-IBS). However, their subset characteristic profile in this kind of disease remains unclear. Thus the current study’s aim is to investigate the functionally predominant subset and its role in PI-IBS.

Methods

The total T cells were collected from the peripheral blood of patients with PI-IBS. The peripheral proportion of Vδ1 and Vδ2 subset was detected by FACS after stained with anti δ1-PE and anti δ2-APC. The local colonic proportion of this two subsets were measured under laser confocal fluorescence microscope. Vδ1 γδ T cells were enriched from the total peripheral T cells by minoantibody-immuno-microbeads (MACS) method and cultured, functionally evaluated by CCK-8 assay (proliferation), CD69/CD62L molecules expression assay (activation) and ELISA (IL-17 production) respectively.

Results

1. Vδ1 γδ T cells significantly increased while Vδ2 γδ T cells remained unchanged in both the peripheral blood and local colonic tissue from PI-IBS patients (p < 0.05). 2. When cultured in vitro, the Vδ1 γδ T cells remarkably proliferated, activated and produced IL-17 (p < 0.05).

Conclusions

Our results suggest that Vδ1 γδ T cells was the predominant γδ T cells subset in both peripheral and intestinal tissue, and was the major IL-17 producing γδ T cells in PI-IBS.

The E protein-TCF1 axis controls γδ T cell development and effector fate

TCF1 plays a critical role in T lineage commitment and the development of αβ lineage T cells, but its role in γδ T cell development remains poorly understood. Here, we reveal a regulatory axis where T cell receptor (TCR) signaling controls TCF1 expression through an E-protein-bound regulatory element in the Tcf7 locus, and this axis regulates both γδ T lineage commitment and effector fate. Indeed, the level of TCF1 expression plays an important role in setting the threshold for γδ T lineage commitment and modulates the ability of TCR signaling to influence effector fate adoption by γδ T lineage progenitors. This finding provides mechanistic insight into how TCR-mediated repression of E proteins promotes the development of γδ T cells and their adoption of the interleukin (IL)-17-producing effector fate. IL-17-producing γδ T cells have been implicated in cancer progression and in the pathogenesis of psoriasis and multiple sclerosis.

Epidermal resident γδ T cell development and function in skin

Epidermal resident γδ T cells, or dendritic epidermal T cells (DETCs) in mice, are a unique and conserved population of γδ T cells enriched in the epidermis, where they serve as the regulators of immune responses and sense skin injury. Despite the great advances in the understanding of the development, homeostasis, and function of DETCs in the past decades, the origin and the underlying molecular mechanisms remain elusive. Here, we reviewed the recent research progress on DETCs, including their origin and homeostasis in the skin, especially at transcriptional and epigenetic levels, and discuss the involvement of DETCs in skin diseases.

Dendritic Epidermal T Cells in Allergic Contact Dermatitis

Allergic contact dermatitis (ACD) is a common inflammatory skin disease with a prevalence of approximately 20% in the European population. ACD is caused by contact allergens that are reactive chemicals able to modify non-immunogenic self-proteins to become immunogenic proteins. The most frequent contact allergens are metals, fragrances, and preservatives. ACD clinically manifests as pruritic eczematous lesions, erythema, local papules, and oedema. ACD is a T cell-mediated disease, involving both CD4⁺ and CD8⁺ T cells. In addition, γδ T cells appear to play an important role in the immune response to contact allergens. However, it is debated whether γδ T cells act in a pro- or anti-inflammatory manner. A special subset of γδ T cells, named dendritic epidermal T cells (DETC), is found in the epidermis of mice and it plays an important role in immunosurveillance of the skin. DETC are essential in sensing the contact allergen-induced stressed environment. Thus, allergen-induced activation of DETC is partly mediated by numerous allergen-induced stress proteins expressed on the keratinocytes (KC). Several stress proteins, like mouse UL-16-binding protein-like transcript 1 (Mult-1), histocompatibility 60 (H60) and retinoic acid early inducible-1 (Rae-1) α-ε family in mice and major histocompatibility complex (MHC) class I-chain-related A (MICA) in humans, are upregulated on allergen-exposed KC. Allergen-induced stress proteins expressed on the KC are consequently recognized by NKG2D receptor on DETC. This review focuses on the role of γδ T cells in ACD, with DETC in the spotlight, and on the role of stress proteins in contact allergen-induced activation of DETC.

Recent advances in understanding the development and function of γδ T cells

γδ T cells are a subset of T cells with attributes of both the innate and adaptive arms of the immune system. These cells have long been an enigmatic and poorly understood component of the immune system and many have viewed them as having limited importance in host defense. This perspective persisted for some time both because of critical gaps in knowledge regarding how the development of γδ T cells is regulated and because of the lack of effective and sophisticated approaches through which the function of γδ T cells can be manipulated. Here, we discuss the recent advances in both of these areas, which have brought the importance of γδ T cells in both productive and pathologic immune function more sharply into focus.

Ultrasmall silica nanoparticles directly ligate the T cell receptor complex

The impact of ultrasmall nanoparticles (<10-nm diameter) on the immune system is poorly understood. Recently, ultrasmall silica nanoparticles (USSN), which have gained increasing attention for therapeutic applications, were shown to stimulate T lymphocytes directly and at relatively low-exposure doses. Delineating underlying mechanisms and associated cell signaling will hasten therapeutic translation and is reported herein. Using competitive binding assays and molecular modeling, we established that the T cell receptor (TCR):CD3 complex is required for USSN-induced T cell activation, and that direct receptor complex-particle interactions are permitted both sterically and electrostatically. Activation is not limited to αβ TCR-bearing T cells since those with γδ TCR showed similar responses, implying that USSN mediate their effect by binding to extracellular domains of the flanking CD3 regions of the TCR complex. We confirmed that USSN initiated the signaling pathway immediately downstream of the TCR with rapid phosphorylation of both ζ-chain-associated protein 70 and linker for activation of T cells protein. However, T cell proliferation or IL-2 secretion were only triggered by USSN when costimulatory anti-CD28 or phorbate esters were present, demonstrating that the specific impact of USSN is in initiation of the primary, nuclear factor of activated T cells-pathway signaling from the TCR complex. Hence, we have established that USSN are partial agonists for the TCR complex because of induction of the primary T cell activation signal. Their ability to bind the TCR complex rapidly, and then to dissolve into benign orthosilicic acid, makes them an appealing option for therapies targeted at transient TCR:CD3 receptor binding.

Control of Intra-Thymic αβ T Cell Selection and Maturation by H3K27 Methylation and Demethylation

In addition to transcription factor binding, the dynamics of DNA modifications (methylation) and chromatin structure are essential contributors to the control of transcription in eukaryotes. Research in the past few years has emphasized the importance of histone H3 methylation at lysine 27 for lineage specific gene repression, demonstrated that deposition of this mark at specific genes is subject to differentiation-induced changes during development, and identified enzymatic activities, methyl transferases and demethylases, that control these changes. The present review discusses the importance of these mechanisms during intrathymic αβ T cell selection and late differentiation.

miR-125b-5p and miR-99a-5p downregulate human γδ T-cell activation and cytotoxicity

As an important component of innate immunity, human circulating γδ T cells function in rapid responses to infections and tumorigenesis. MicroRNAs (miRNAs) play a critical regulatory role in multiple biological processes and diseases. Therefore, how the functions of circulating human γδ T cells are regulated by miRNAs merits investigation. In this study, we profiled the miRNA expression patterns in human peripheral γδ T cells from 21 healthy donors and identified 14 miRNAs that were differentially expressed between peripheral αβ T cells and γδ T cells. Of the 14 identified genes, 7 miRNAs were downregulated, including miR-150-5p, miR-450a-5p, miR-193b-3p, miR-365a-3p, miR-31-5p, miR-125b-5p and miR-99a-5p, whereas the other 7 miRNAs were upregulated, including miR-34a-5p, miR-16-5p, miR-15b-5p, miR-24-3p, miR-22-3p, miR-22-5p and miR-9-5p, in γδ T cells compared with αβ T cells. In subsequent functional studies, we found that both miR-125b-5p and miR-99a-5p downregulated γδ T cell activation and cytotoxicity to tumor cells. Overexpression of miR-125b-5p or miR-99a-5p in γδ T cells inhibited γδ T cell activation and promoted γδ T cell apoptosis. Additionally, miR-125b-5p knockdown facilitated the cytotoxicity of γδ T cells toward tumor cells in vitro by increasing degranulation and secretion of IFN-γ and TNF-α. Our findings improve the understanding of the regulatory functions of miRNAs in γδ T cell activation and cytotoxicity, which has implications for interventional approaches to γδ T cell-mediated cancer therapy.

Heat shock protein 70 protects mouse against post-infection irritable bowel syndrome via up-regulating intestinal γδ T cell's Th17 response

Background

This study investigated the role of HSP70 in modulating intestinal γδ T cells’ Th17 response in Trichinella spiralis-induced PI-IBS mice model.

Methods

The intestinal HSP70’s expression and mRNA level were measured by Western blot and RT-PCR. The intestinal γδ T cell’s morphological changes were analyzed using immunofluorescence staining and confocal laser scanning microscope. The pro-inflammatory cytokines’ level was detected by ELISA. The isolated and purified γδ T cells were pre-incubated with HSP70 and their functions including proliferation, apoptosis, activation and production of IL-17 were also detected.

Results

Heat treatment augmented intestinal HSP70 expression and alleviated the clinical presentations in PI-IBS mice. Meanwhile, intestinal γδ T cells and local IL-17 level were increased by pre-induction of HSP70. HSP70 promoted the proliferation of PI-IBS mice’s intestinal γδ T cells, inhibited the apoptosis and stimulated these cells to secret IL-17 rather than IFN-γ.

Conclusion

Our results suggest that HSP70 plays a protective role via up-regulating intestinal γδ T cell’s Th17 response in PI-IBS mice.

γδ T cells in homeostasis and host defence of epithelial barrier tissues

Epithelial surfaces line the body and provide a crucial interface between the body and the external environment. Tissue-resident epithelial γδ T cells represent a major T cell population in the epithelial tissues and are ideally positioned to carry out barrier surveillance and aid in tissue homeostasis and repair. In this Review, we focus on the intraepithelial γδ T cell compartment of the two largest epithelial tissues in the body - namely, the epidermis and the intestine - and provide a comprehensive overview of the crucial contributions of intraepithelial γδ T cells to tissue integrity and repair, host homeostasis and protection in the context of the symbiotic relationship with the microbiome and during pathogen clearance. Finally, we describe epithelium-specific butyrophilin-like molecules and briefly review their emerging role in selectively shaping and regulating epidermal and intestinal γδ T cell repertoires.