Milestone: Researchers restore the “body shield”
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The nervous system controls the immune system and a spinal cord injury considerably lowers its power. Patients with a spinal cord injury are therefore more likely to catch an infection, almost half of them will contract a lung infection (pneumonia), and as a result will recover less than they could have. Preventing the lowering of the immune system will therefore reduce the number of infections, the number of early death and result in a substantial gain of function. Despite its clinical relevance, the underlying mechanisms on how a spinal cord injury triggers a systemic immune paralysis remained elusive.
Wings for Life supported an international and interdisciplinary collaboration of several scientists and institutions led by Jan Schwab helping to understand and revert the immune paralysis after spinal cord injury. The results of this massive endeavor will be published in Nature Neuroscience.
Interplay from the nervous system and the immune system
The autonomic nervous system is a control system that acts mostly unconsciously, it regulates functions of the blood vessels and glands and thus influences the function of internal organs. The autonomic nervous system has two branches: the sympathetic system and the parasympathetic system that innervate each internal organ. One of these organs is the adrenal gland, an endocrine organ located above the kidneys that produces a variety of hormones and regulates the activity of the immune system.
The immune paralysis and the adrenal gland
A spinal cord injury disconnects the brain from the part of the spinal cord below the injury affecting also the sympathetic nervous system. Consequently, the regulation normally coming from the brain is totally lost or skewed. The team of scientists found this loss of control is the very mechanism that drives the immune paralysis seen after a spinal cord injury in an upper thoracic level.
The uncontrolled sympathetic activity leads to a dysregulation of the adrenal gland, which results in a severe imbalance of the hormones it secretes. This imbalance totally disrupts the activity of the immune system.
In this project the researchers severed all connections between the sympathetic nerve system and the gland, thus the gland worked without any influence of the sympathetic system. This restored the hormone levels to a nearly physiological level and resulted in relieving the immune paralysis and prevention of any lung infection.
These results open new directions and alternatives to the classic antibiotic treatment, which can be ineffective and can lead to antibiotic resistance. This project challenges the current understanding and offers a novel potential therapeutic strategy for preventing infections in patients after spinal cord injury.
Source: “Spinal cord injury-induced immunodeficiency is mediated by a sympathetic-neuroendocrine adrenal reflex”. Prüss H, Tedeschi A, Thiriot A, Lynch L, Loughhead SM, Stutte S, Mazo IB, Kopp MA, Brommer B, Blex C, Geurtz LC, Liebscher T, Niedeggen A, Dirnagl U, Bradke F, Volz MS, DeVivo MJ, Chen Y, Andrian UH, Schwab JM. Nature Neuroscience, September, 2017.