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24 February 2009 How photons modulate wound healing via the immune system
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The immune system is a diverse group of cells that recognize and attack foreign substances, pathogenic organisms and cancer cells. It also produces inflammation, an essential component of the wound healing process and, following the resolution of inflammation, plays a crucial role in the control of granulation tissue formation. Granulation tissue is the precursor of scar tissue. Injured skin and mucous membranes generally heal rapidly. However, some wounds are either slow to heal or fail to heal while in others overgrowth of scar tissue occurs, resulting in the production of either hypertophic or keloid scars. The modulation of wound healing in such conditions is clinically important and may even be vital. Evidence will be presented that phototherapy can modulate wound healing, and that changes induced in the immune system, in particular the secretion of soluble protein mediators including cytokines, may be involved in this modulation. The immune system has peripheral and deep components. The former, being located mainly in the skin and mucous membranes, are readily accessible to photons, which can affect them directly. The components of the immune system are linked by lymphatic vessels and blood vessels, which include many capillaries located in the sub-epithelial connective tissues of the skin and mucous membranes. The superficial location of these capillaries provides the immune cells and molecules in transit through them with ready access to photons. When these cells and molecules, some modified by exposure to photons, reach susceptible cells such as lymphocytes in the deeper parts of the immune system and cells of injured tissues, they can modify their activity. In addition to having direct effects on peripheral cells, photons can thus also produce indirect effects on cells too distant for the photons to reach them. For example, cytokines released from peripheral macrophages in response to the direct action of photons can be transported to and affect other cells, including fibroblasts of injured tissues, that have not been exposed to photons. It is therefore possible for injuries other than those directly exposed to phototherapy to be affected by it indirectly.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mary Dyson "How photons modulate wound healing via the immune system", Proc. SPIE 7178, Biophotonics and Immune Responses IV, 717805 (24 February 2009);


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