The Effects of Light-Emitting Diode Irradiation at 610 nm and 710 nm on Murine T-Cell Subset Populations

Abstract

Objective: The aim of this study was to investigate the effects of light-emitting diode (LED) irradiation (radiant power, 0.047 mW; irradiation area, 1.13 cm²) at 610 nm and 710 nm on T-lymphocyte subset populations and cytokine expression using an in vivo rat model. Background Data: The proliferation of CD4+ T lymphocytes was induced by polychromatic visible polarized light at the range of 540–780 nm in a previous study, but the specific target wavelength for this effect has not yet been identified. Methods: Before and after 4 weeks of LED phototherapy, whole blood samples were collected from 610 nm, 710 nm, and control groups. The percentages of CD4+ and CD8+ T lymphocyte populations were determined by flow cytometry. The transcript levels of representative cytokines of CD4+ T-cell (interleukin [IL]-4, interferon [IFN]γ) and proinflammatory cytokines (IL-1β, IL-6) were assessed with the reverse transcriptase–polymerase chain reaction. Results: The population of CD4+ T cells increased significantly in 710 nm group on day 28 (p < 0.05), but it did not increase in the 610 nm or control group. The population of CD8+ T cells did not show any significant change after irradiation in all groups. The mRNA expression of IL-4 increased in both the 610 nm and 710 nm groups compared to the control group, but IFNγ was not detected in any group. The transcripts of IL-1β and IL-6 were slightly induced in the 710 nm group. Conclusion: The in vivo irradiation of 710 nm wavelength LED significantly increases the population of murine CD4+ T cells, which suggests that this new phototherapeutic regimen might be promising for CD4+ T lymphocyte–mediated immune modulation therapy.