γδ T cells aggravate blood-brain-barrier injury via IL-17A in experimental ischemic stroke

T cell interactions with microglia in immune-inflammatory processes of ischemic stroke

The primary mechanism of secondary injury after cerebral ischemia may be the brain inflammation that emerges after an ischemic stroke, which promotes neuronal death and inhibits nerve tissue regeneration. As the first immune cells to be activated after an ischemic stroke, microglia play an important immunomodulatory role in the progression of the condition. After an ischemic stroke, peripheral blood immune cells (mainly T cells) are recruited to the central nervous system by chemokines secreted by immune cells in the brain, where they interact with central nervous system cells (mainly microglia) to trigger a secondary neuroimmune response. This review summarizes the interactions between T cells and microglia in the immune-inflammatory processes of ischemic stroke. We found that, during ischemic stroke, T cells and microglia demonstrate a more pronounced synergistic effect. Th1, Th17, and M1 microglia can co-secrete pro-inflammatory factors, such as interferon-γ, tumor necrosis factor-α, and interleukin-1β, to promote neuroinflammation and exacerbate brain injury. Th2, Treg, and M2 microglia jointly secrete anti-inflammatory factors, such as interleukin-4, interleukin-10, and transforming growth factor-β, to inhibit the progression of neuroinflammation, as well as growth factors such as brain-derived neurotrophic factor to promote nerve regeneration and repair brain injury. Immune interactions between microglia and T cells influence the direction of the subsequent neuroinflammation, which in turn determines the prognosis of ischemic stroke patients. Clinical trials have been conducted on the ways to modulate the interactions between T cells and microglia toward anti-inflammatory communication using the immunosuppressant fingolimod or overdosing with Treg cells to promote neural tissue repair and reduce the damage caused by ischemic stroke. However, such studies have been relatively infrequent, and clinical experience is still insufficient. In summary, in ischemic stroke, T cell subsets and activated microglia act synergistically to regulate inflammatory progression, mainly by secreting inflammatory factors. In the future, a key research direction for ischemic stroke treatment could be rooted in the enhancement of anti-inflammatory factor secretion by promoting the generation of Th2 and Treg cells, along with the activation of M2-type microglia. These approaches may alleviate neuroinflammation and facilitate the repair of neural tissues.

The immunomodulatory mechanism of acupuncture treatment for ischemic stroke: research progress, prospects, and future direction

Ischemic stroke (IS) is one of the leading causes of death and disability. Complicated mechanisms are involved in the pathogenesis of IS. Immunomodulatory mechanisms are crucial to IS. Acupuncture is a traditional non-drug treatment that has been extensively used to treat IS. The exploration of neuroimmune modulation will broaden the understanding of the mechanisms underlying acupuncture treatment. This review summarizes the immune response of immune cells, immune cytokines, and immune organs after an IS. The immunomodulatory mechanisms of acupuncture treatment on the central nervous system and peripheral immunity, as well as the factors that influence the effects of acupuncture treatment, were summarized. We suggest prospects and future directions for research on immunomodulatory mechanisms of acupuncture treatment for IS based on current progress, and we hope that these will provide inspiration for researchers. Additionally, acupuncture has shown favorable outcomes in the treatment of immune-based nervous system diseases, generating new directions for research on possible targets and treatments for immune-based nervous system diseases.

The immune system in neurological diseases: What innate-like T cells have to say

The immune system classically consists of 2 lines of defense, innate and adaptive, both of which interact with one another effectively to protect us against any pathogenic threats. Importantly, there is a diverse subset of cells known as innate-like T cells that act as a bridge between the innate and adaptive immune systems and are pivotal players in eliciting inflammatory immune responses. A growing body of evidence has demonstrated the regulatory impact of these innate-like T cells in central nervous system (CNS) diseases and that such immune cells can traffic into the brain in multiple pathological conditions, which can be typically attributed to the breakdown of the blood-brain barrier. However, until now, it has been poorly understood whether innate-like T cells have direct protective or causative properties, particularly in CNS diseases. Therefore, in this review, our attention is focused on discussing the critical roles of 3 unique subsets of unconventional T cells, namely, natural killer T cells, γδ T cells, and mucosal-associated invariant T cells, in the context of CNS diseases, disorders, and injuries and how the interplay of these immune cells modulates CNS pathology, in an attempt to gain a better understanding of their complex functions.

Inhibition of γδ T Cells Alleviates Blood-Brain Barrier in Cardiac Arrest and Cardiopulmonary Resuscitation in Mice

Ischemia/reperfusion (I/R) injury is the leading cause of death following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). γδT cells are suggested to aggravate blood-brain barrier (BBB) injury in various pathological processes. We herein investigate the effects of γδT cells inhibitor (UC7-13D5) against I/R injury post-CA/CPR. C57BL/6 mice were subjected to CA through injection of KCL (70 μL of 0.5 mol/L) and cessation of mechanical ventilation followed by CPR. Flow cytometry was performed to measure the proportion of CD3-positive cells after intraperitoneal injection of 200 μg UC7-13D5 at 6 h, 24 h, and 48 h post-resuscitation into mice. Neurological scores and modified neurological severity scores were assessed to examine neurological functions. Brain edema was estimated via brain water content measurements. Immunohistochemistry of caspase-3 and immunofluorescence staining of claudin-1, ZO-1 and CD31 were performed to detect neuronal apoptosis, BBB integrity and angiogenesis. Microvascular morphology in the cortical area was assessed via H&E staining. Oxidative stress was determined by measuring malondialdehyde, myeloperoxidase, xanthine oxidase, superoxide dismutase, and glutathione peroxidase activities. Western blotting was performed to measure the protein levels of Nuclear factor-E2-related factor 2 (Nrf2) and Heme oxygenase-1 (HO-1). UC7-13D5 effectively depleted γδT cells. Inhibition of γδT cells improved neurological deficits and reduced brain edema post-CA/CPR. γδT cells depletion attenuated neuronal apoptosis, BBB disruption and oxidative stress and promoted angiogenesis following CA/CPR. Inhibition of γδT cells facilitated the activation of the Nrf2/HO-1 pathway in CA/CPR-induced mice. Inhibition of γδT cells alleviates neurological deficits and cerebral edema in mice with CA/CPR by inhibiting neuronal apoptosis, BBB disruption and oxidative stress, and promoting angiogenesis via activation of the Nrf2/HO-1 pathway.

Unconventional T cells in brain homeostasis, injury and neurodegeneration

The interaction between peripheral immune cells and the brain is an important component of the neuroimmune axis. Unconventional T cells, which include natural killer T (NKT) cells, mucosal-associated invariant T (MAIT) cells, γδ T cells, and other poorly defined subsets, are a special group of T lymphocytes that recognize a wide range of nonpolymorphic ligands and are the connection between adaptive and innate immunity. Recently, an increasing number of complex functions of these unconventional T cells in brain homeostasis and various brain disorders have been revealed. In this review, we describe the classification and effector function of unconventional T cells, review the evidence for the involvement of unconventional T cells in the regulation of brain homeostasis, summarize the roles and mechanisms of unconventional T cells in the regulation of brain injury and neurodegeneration, and discuss immunotherapeutic potential as well as future research goals. Insight of these processes can shed light on the regulation of T cell immunity on brain homeostasis and diseases and provide new clues for therapeutic approaches targeting brain injury and neurodegeneration.

Role of IL-17A in different stages of ischemic stroke

Interleukin-17A (IL-17A) plays an important role in the progression of ischemic stroke. IL-17A mediates the endothelial inflammatory response, promotes water and sodium retention, and changes the electrophysiological structure of the atrium, accelerating the progression of ischemic stroke risk factors such as atherosclerotic plaques, hypertension, and atrial fibrillation. In the acute phase of ischemic stroke, IL-17A mediates neuronal injury through neutrophil chemotaxis to the site of injury, the induction of neuronal apoptosis, and activation of the calpain-TRPC-6 (transient receptor potential channel-6) pathway. During ischemic stroke recovery, IL-17A, which is mainly derived from reactive astrocytes, promotes and maintains the survival of neural precursor cells (NPCs) in the subventricular zone (SVZ), neuronal differentiation, and synapse formation and participates in the repair of neurological function. Therapies targeting IL-17A-associated inflammatory signaling pathways can reduce the risk of ischemic stroke and neuronal damage and are a new therapeutic strategy for ischemic stroke and its risk factors. In this paper, we will briefly discuss the pathophysiological role of IL-17A in ischemic stroke risk factors, acute and chronic inflammatory responses, and the potential therapeutic value of targeting IL-17A.

IL-17 and IL-17-producing cells in protection versus pathology

IL-17 cytokine family members have diverse biological functions, promoting protective immunity against many pathogens but also driving inflammatory pathology during infection and autoimmunity. IL-17A and IL-17F are produced by CD4⁺ and CD8⁺ T cells, γδ T cells, and various innate immune cell populations in response to IL-1β and IL-23, and they mediate protective immunity against fungi and bacteria by promoting neutrophil recruitment, antimicrobial peptide production and enhanced barrier function. IL-17-driven inflammation is normally controlled by regulatory T cells and the anti-inflammatory cytokines IL-10, TGFβ and IL-35. However, if dysregulated, IL-17 responses can promote immunopathology in the context of infection or autoimmunity. Moreover, IL-17 has been implicated in the pathogenesis of many other disorders with an inflammatory basis, including cardiovascular and neurological diseases. Consequently, the IL-17 pathway is now a key drug target in many autoimmune and chronic inflammatory disorders; therapeutic monoclonal antibodies targeting IL-17A, both IL-17A and IL-17F, the IL-17 receptor, or IL-23 are highly effective in some of these diseases. However, new approaches are needed to specifically regulate IL-17-mediated immunopathology in chronic inflammation and autoimmunity without compromising protective immunity to infection.