Reflex neural circuits affect innate and adaptive immune responses and the development of inflammatory diseases. It is well known that the nervous system is the target of autoimmune reactions, as in multiple sclerosis and myasthenia gravis, and inflammation may contribute to the development of neuro degenerative disorders such as Alzheimer disease. The interesting new developments are the elucidation of molecular communications between the nervous and immune systems, often via secreted molecules. The idea that neural circuits modulate immunity and the immune system alters neural functions has fascinated biologists and clinicians for decades. Some of the earliest findings suggesting the existence of such interactions were clinical observations that psychological stresses affected the severity of allergic (Th2-dominant) and contact sensitivity (Th1-dominant) reactions. These associations were usually interpreted to reflect the actions of neu ropeptides, produced during psychological alterations, on lymphocytes and other immune cells. More recently, sophisticated genetic and other tools have been used to dissect bidirectional neural-immune interactions with greater precision. Among the findings potentially relevant to the development of disease states, the following are some interesting examples.

• Activation of the efferent vagus nerve inhibits the production of pro-inflammatory innate cytokines such as TNF, providing a novel mechanism for regulating inflammation. This has led to clinical trials of vagus nerve stimulation in patients with rheumatoid arthritis.

• Cholinergic and adrenergic signals in the spleen regulate antibody production.

 • Neuropeptides produced in response to microbes and other local stimuli influence the activation of type 2 innate lymphoid cells in the airways and hence type 2 immunity, the basis of allergic diseases.

• The gut microbiome induces signals from enteric nerves that induce macrophages to develop an anti-inflammatory and tissue-protective phenotype and regulates the balance between pro-inflammatory T h17 cells and protective Treg cells. Thus, the micro biome uses neural circuits to maintain immune homeostasis in the gut, raising the possibility that abnormalities in this circuit contribute to intestinal inflammation.

 • In addition to these examples of neural signals affecting immune responses, the converse is also true, that immune reactions alter neurological and psychological functions. For instance, neuronal development is regulated by complement breakdown products and cytokines, and cytokines produced by immune cells may influence cognitive functions such as memory and social behavior.

Many other neural-immune interactions have been described, and their impact on autoimmune and allergic diseases is being explored. The hope is that elucidation of these pathways will lead to the development of new classes of therapies for these diseases. 

مواضيع ذات صلة

Congenital Immunodeficiencies: Defects in Lymphocyte Maturation

Congenital Immunodeficiencies: Defects in Innate Immunity

Congenital (Primary) Immunodeficiencies

Disorders of Neutrophils

Cell Surface Receptors

Sepsis

Acute Inflammation

Diseases Caused by T Lymphocytes

Etiology, Examples, and Therapy of Immune Complex–Mediated Diseases

Examples and Treatment of Diseases Caused by Cell- or Tissue-Specific Antibodies

Mechanisms of Antibody-Mediated Tissue Injury and Disease

Hypersensitivity Disorders Caused by Immune Responses : Clinical Syndromes and Therapy