Immunity and the Nervous System: A Collaborative Network

The immune system and the nervous system, once viewed as separate entities, are now understood to be intricately connected. This complex interplay influences health and disease in various ways.

The Blood-Brain Barrier: A Selective Gateway

The central nervous system (CNS) is protected by the blood-brain barrier (BBB). This highly selective barrier, formed by specialized endothelial cells with tight junctions, restricts the movement of molecules and immune cells from the bloodstream into the brain. This safeguards the delicate neuronal environment from potentially harmful immune responses.

Protective barriers of the brain

Immune Guardians Within the CNS

Despite the BBB, the CNS is not entirely devoid of immune activity. Specialized immune cells called microglia and astrocytes reside within the CNS and play a critical role in maintaining tissue health and responding to injury or infection. Microglia act as sentinels, constantly scanning for pathogens and damaged cells. Upon detection of threats, they can activate immune responses or promote repair processes.

Channels of Communication

Communication between the immune and nervous systems occurs through several mechanisms:

  • Autonomic nervous system: This network of nerves directly innervates lymphoid organs, influencing immune cell activity through neurotransmitters.
  • Cytokines and chemokines: These signaling molecules, produced by both immune and nervous system cells, coordinate responses across both systems.
  • Hypothalamic-pituitary-adrenal (HPA) axis: This neuroendocrine pathway regulates stress response and can modulate immune function through hormones.

HPA axis and autonomic nervous system (i.e., sympathetic nervous system and parasympathetic nervous system) plays central role in regulating peripheral immune cells after TBI. After a TBI, the sympathetic and parasympathetic nervous systems stimulate the secondary lymphoid organs via their neurotransmitters (norepinephrine and acetycholine respectively) leading to a state of immunodepression due to the loss of inflammatory functions of the leukocytes. Post-traumatic activation of HPA axis leads to CIRCI and deepens the immunosuppressive state. α/β AR, α/β adrenergic receptor; α7nAchR, α7 subunit of the acetyl choline receptor.

Immune Dysfunction and Neurological Disorders

Disruptions in the delicate balance between the immune and nervous systems can contribute to various neurological disorders:

  • Autoimmune diseases: In conditions like multiple sclerosis, the immune system mistakenly attacks components of the CNS, leading to damage and neurological deficits.
  • Neurodegenerative diseases: Chronic inflammation, potentially driven by a dysregulated immune response, is implicated in the progression of Alzheimer's and Parkinson's diseases.

Research is ongoing to better understand the immune system's role in neurological disorders. Maxanim (Gentaur Group) is a company supplying resources for this research. Click here for more info.

| The neuroimmune connections between CRH and MCs associated with central and peripheral inflammation result in neurological disorders. The schematic diagram shows the effect of stress-induced neuroimmune interactions between CRH and MCs and the link to neurological diseases. Stress conditions activate the HPA axis to induce neuroimmune communication between CRH and MCs to release numerous inflammatory mediators from MCs upon their activation, which in turn disrupts the BBB, leading to neuroinflammatory processes associated with neurological diseases. AD: Alzheimer's disease; ASD: autism spectrum disorder; BBB: blood-brain barrier; CRH: corticotropin-releasing hormone; HPA: hypothalamicpituitary-adrenal; IL: interleukin; MC: mast cell; MS: multiple sclerosis; NT: neurotensin; PD: Parkinson disease; POCD: postoperative cognitive dysfunction; TNF: tumor necrosis factor.

Future Directions

Understanding the intricate interplay between immunity and the nervous system holds promise for new therapeutic approaches. By deciphering the communication pathways, researchers aim to develop targeted interventions for neurological disorders and more effectively modulate immune responses.

Explore how the nervous system may influence the immune system in this video.



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Immunity and the Nervous System: A Collaborative Network
Gen store May 31, 2024
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