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Light and Immunity

Discussion in 'Immunology and Rheumatology' started by Egyptian Doctor, Mar 25, 2011.

  1. Egyptian Doctor

    Egyptian Doctor Moderator Verified Doctor

    Mar 21, 2011
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    In mammals, such as human beings, sleep, hormone levels, body temperature, immunity, etc. show circadian rhythm. (24-hour cycle).

    The photoreceptors in the retina convert visible rays into electrical signals. The signals move to the visual cortex which deciphers the image. However, there is an alternate pathway which takes the signals to the suprachiasmatic nucleus (SCN) in the hypothalamus. It is this, which governs circadian rhythm.

    Melatonin, norepinephrine, and acetylcholine level decrease under light, on the other hand cortisol, serotonin, GABA, and dopamine levels rise. Melatonin receptor subtypes have been detected on lymphoid tissues. The resulting neuroendocrine changes, modulate immunity. Clinically blind people also show melatonin suppression in the presence of light. Smaller wavelength visible rays, such as blue light, have a stronger effect on melatonin suppression. Some people recommend blue -filter goggles for an hour or two before bedtime. It will raise melatonin levels.Melatonin aids sleep. Studies suggest there is a non-rod non-cone photo pigment for melatonin suppression. Free radical scavenging action of melatonin indirectly assists immunity in protecting the body.

    Visible light (400-700 nm i.e VIBGYOR) can enter epidermal and dermal layers of the skin. They perhaps act on circulating lymphocytes to regulate the immune function. In contrast to visible light, exposure to UV-B (280-320 nm) and UV-A (320-400 nm) radiation alters the normal human immune function by a skin mediated response mainly through their action on the antigen-presenting Langerhans cells and keratinocytes. Each UV subtype (B, A) induces an immunosuppressive response but by differing mechanisms involving the regulation of differing interleukins and growth factors. Some beneficial effects observed in humans are: inhibition of allergic contact dermatitis; inhibition of delayed hypersensitivity to an injected antigen and prolongation of skin-graft survival. However, it also promotes tumorigenesis.

    Source : Interesting Medical Facts

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  2. Aboyamen

    Aboyamen Moderator

    Mar 28, 2011
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    Thanks alot for the topic

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