Helium-neon laser irradiation induces effects on cytokine production at the protein and the mRNA level

Abstract The construction of an in vitro model allowed an investigation of the basic functions of immunocompetent cells after laser irradiation. Among low-energy laser sources, the helium-neon (He-Ne) laser, with a wavelength of 632.8 nm, has often been found to produce photobiological effects including evidence of interference with immunological functions. Previous experiments revealed an influence of He-Ne laser irradiation on concentrations of interleukin-lα (IL-lα. tumor necrosis factor-α (TNF-α, interleukin-2 (IL-2), and interferon-γ (IFN-γ) in supernatants of cultures of human peripheral blood mononuclear cells (PBMC) with increased cytokine concentrations after irradiation of 18.9 J/cm² and decreased concentrations after irradiation of 37.8 J/cm². Now, the mechanisms involved were studied. Results showed that cytokine production of cells stimulated with phytohemagglutinin (PHA), concanavalin A (Con A), or bacterial lipopolysaccharide (LPS) was altered significantly after laser irradiation but not after stimulation with staphylococcus aureus enterotoxin B (SEB). In situ hybridization of IFN-γ mRNA producing PBMC revealed that the number of positive cells was modulated similarly. The results were identical in cultures of enriched monocytic (Mφ) or enriched T cells. Cells of the human monocytic cell line Mono Mac 6 were also influenced after LPS stimulation, whereas constitutively 1L-2-producing Jurkat cells were not influenced by laser irradiation at any energy density. Analysis of the IL-2 receptor (IL-2R) and intercellular adhesion molecule-1 (ICAM-I) expression in PBMC showed partial down-regulation of both receptors at 37.8 J/cm², but only after stimulation with PHA. Collected data demonstrated that He-Ne laser irradiation induces functional changes of stimulated PBMC both on protein production and at the mRNA level.