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The systemic mechanisms of the wound healing effect of low intensity lasers remain largely uninvestigated. The goal of this randomized, placebo controlled, double blind study is to prove that irradiation of a small area of the human body with visible and infrared polarized (VIP) light (400-3400 nm, 95% polarization, 40 mW cm(2), 12 J cm(2)) leads to an increase of the growth promoting (GP) activity of the entire circulating blood for primary cultures of human keratinocytes (KCs). Thirty minutes after the VIP-irradiation of a sacral area of volunteers, the GP activity of circulating blood was seen to increase through the elevation of the number of KCs cultured with the isolated plasma by 20 +/- 3%, p < 0.001. A similar increase in GP activity was seen in plasma derived from the in vitro irradiated blood of each volunteer, and from the mixture of irradiated and non-irradiated autologous blood 1:10. Enhanced GP activity was also recorded at 24 h after the 1st and 4-9th daily phototherapeutic sessions. Hence, exposure of volunteers to VIP light leads to a fast increase in the GP activity of the entire circulating blood for human KCs in vitro, which is a consequence of the transcutaneous photomodification of blood and its effect on the rest of the circulating blood volume.

The immunological effects of visible and infrared light from laser and non-laser sources have remained insufficiently studied, which has restricted the use of light in the treatment of diseases associated with immune system disorders. The present randomised, placebo-controlled double-blind trial was designed to study changes in the humoral immunity of a large group of volunteers after exposure of a small body area to polychromatic visible and infrared polarized (VIP) and non-polarized (VInP) light (400-3400 nm, 95% polarization, 40 mW cm(-2), 12 J cm(-2) and 400-3400 nm, no polarization, 38 mW cm(-2), 11.2 J cm(-2), respectively). Serum immunoglobulins (Ig) M, A, and G were determined turbidimetrically, and the immune complexes (ICs) by precipitation with 5% polyethylene glycol and subsequent spectrophotometric analysis. A single VIP irradiation induced an average rise in serum IgM levels of 13% (p < 0.05). By the end of the 10 day course, it has exceeded the baseline level by 26%, with an increase in IgA levels of 17 and 12% (p < 0.04) one week after the last session. In subjects with a high IC content, it decreased rapidly to the normal level. A single exposure of volunteers to VInP light rapidly produced changes similar to those observed on VIP irradiation, but with an increase in IgM 2.3 to 3 times lower, independent of the initial levels. On the other hand, VInP light exposure decreased the IC content more than VIP light.

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