Group 2 innate lymphoid cells promote inhibitory synapse development and social behavior

Cross-regulation between the nervous system and type 2 immunity

Interactions between the nervous and immune systems are critical to healthy physiology and are altered in many human diseases. Many of the major players in type 2 immune responses, including type 2 lymphocytes and cytokines, mast cells, and immunoglobulin E, have been implicated in neuronal function and behavior. Conversely, neurons in both the central and peripheral nervous systems can affect type 2 immune responses and behaviors relevant to allergy, such as food avoidance. Defining this complex circuitry and its molecular intermediates in physiology may reveal type 2 immunomodulators that can be harnessed for therapeutic benefit in neurologic diseases including Alzheimer's disease, brain injury, and neurodevelopmental disorders. Conversely, modulation of the nervous system may be an important adjunct to treating immunologic disorders including atopic dermatitis, asthma, and food allergy. This Review covers recent work defining how the nervous system can both regulate and be regulated by type 2 immune responses.

Psychedelic control of neuroimmune interactions governing fear

Neuroimmune interactions-signals transmitted between immune and brain cells-regulate many aspects of tissue physiology1, including responses to psychological stress2-5, which can predispose individuals to develop neuropsychiatric diseases6-9. Still, the interactions between haematopoietic and brain-resident cells that influence complex behaviours are poorly understood. Here, we use a combination of genomic and behavioural screens to show that astrocytes in the amygdala limit stress-induced fear behaviour through epidermal growth factor receptor (EGFR). Mechanistically, EGFR expression in amygdala astrocytes inhibits a stress-induced, pro-inflammatory signal-transduction cascade that facilitates neuron-glial crosstalk and stress-induced fear behaviour through the orphan nuclear receptor NR2F2 in amygdala neurons. In turn, decreased EGFR signalling and fear behaviour are associated with the recruitment of meningeal monocytes during chronic stress. This set of neuroimmune interactions is therapeutically targetable through the administration of psychedelic compounds, which reversed the accumulation of monocytes in the brain meninges along with fear behaviour. Together with validation in clinical samples, these data suggest that psychedelics can be used to target neuroimmune interactions relevant to neuropsychiatric disorders and potentially other inflammatory diseases.

Oxytocin-Mediate Modulation of Splenic Immunosuppression in Chronic Social Stress Through Neuroendocrine Pathways

Chronic social stress (CSS) is a significant public health challenge that negatively impacts behavior and immune function through brain-spleen interactions. Oxytocin (OT), a neuropeptide critical for social behavior and immune regulation, is upregulated during CSS, though its underlying mechanisms remain unclear. This study investigates the role of OT in splenic immune modulation using a murine model of CSS. Behavioral evaluations, serum oxytocin quantification, and splenic immunophenotypic analysis were performed. Splenic denervation confirmed OT's neuromodulatory role, whereas OTR antagonism revealed its endocrine function. CSS-induced OT elevation was associated with immunosuppression, characterized by increased Foxp3⁺ regulatory T cells and reduced CD4⁺ T and CD19⁺ B cells. OT also modulated macrophage polarization, inhibiting M1-like (pro-inflammatory) and enhancing M2-like (anti-inflammatory) phenotypes. Denervation or pharmacological blockade of OT signaling partly reversed CSS-induced splenic immunosuppression but adversely affected survival in CSS-exposed mice. Additionally, denervation or OTR antagonism reduced the mice's response to social defeat, as shown by decreased social avoidance behavior. These findings suggest that OT-mediated immunosuppression likely represents a compensatory mechanism in response to chronic social stress. Targeting the OT-immune axis could offer innovative therapeutic approaches for stress-associated disorders by restoring immune homeostasis while maintaining behavioral integrity.

ILC2 instructs neural stem and progenitor cells to potentiate neurorepair after stroke

Stroke affects approximately 1 in 6 individuals globally and is the leading cause of adult disability, which is attributed to neuronal damage and neurological impairments. The mechanisms by which the brain tissue microenvironment supports neurogenesis and neurorepair post-stroke remain to be fully elucidated. In this study, we report that group 2 innate lymphoid cells (ILC2s) accumulate within the lesion core and subventricular zone (SVZ) during brain recovery following cerebral ischemia. Mice with ILC2 deficiency display impaired neurological scoring post-stroke. Mechanistic studies reveal that brain ILC2s enhance the proliferation of neural stem and progenitor cells (NSPCs) through the secretion of amphiregulin (Areg). Adoptive transfer of ILC2s or administration of Areg markedly improves neurological outcomes post-stroke. These findings demonstrate that ILC2s and their secreted products may represent a promising therapeutic strategy for enhancing neurorepair following brain injury.

Enteric neurons and immune cells shape anti-helminth immunity

Wang et al. recently reported that during helminth infection, innate lymphoid cell (ILC)-derived IL-13 is sensed by gut neurons, which in turn secretes CGRP to inhibit ILC2 proliferation and anti-helminth responses. Hence, this study demonstrates a bidirectional crosstalk between enteric neurons and immune cells that regulates type-2 immunity.

The neuroimmune connectome in health and disease

The nervous and immune systems have complementary roles in the adaptation of organisms to environmental changes. However, the mechanisms that mediate cross-talk between the nervous and immune systems, called neuroimmune interactions, are poorly understood. In this Review, we summarize advances in the understanding of neuroimmune communication, with a principal focus on the central nervous system (CNS): its response to immune signals and the immunological consequences of CNS activity. We highlight these themes primarily as they relate to neurological diseases, the control of immunity, and the regulation of complex behaviours. We also consider the importance and challenges linked to the study of the neuroimmune connectome, which is defined as the totality of neuroimmune interactions in the body, because this provides a conceptual framework to identify mechanisms of disease pathogenesis and therapeutic approaches. Finally, we discuss how the latest techniques can advance our understanding of the neuroimmune connectome, and highlight the outstanding questions in the field.

Immune control of brain physiology

The peripheral immune system communicates with the brain through complex anatomical routes involving the skull, the brain borders, circumventricular organs and peripheral nerves. These immune-brain communication pathways were classically considered to be dormant under physiological conditions and active only in cases of infection or damage. Yet, peripheral immune cells and signals are key in brain development, function and maintenance. In this Perspective, we propose an alternative framework for understanding the mechanisms of immune-brain communication. During brain development and in homeostasis, these anatomical structures allow selected elements of the peripheral immune system to affect the brain directly or indirectly, within physiological limits. By contrast, in ageing and pathological settings, detrimental peripheral immune signals hijack the existing communication routes or alter their structure. We discuss why a diversity of communication channels is needed and how they work in relation to one another to maintain homeostasis of the brain.

First responders have it covered

Meningeal innate lymphoid cells guide inhibitory neurons in early life.