Modulation of immune response to induced‐arthritis by low‐level laser therapy

As low‐level laser therapy immune cells responses are not always clarified, this study aimed to evaluate cytokines and immune cells profile after low‐level laser therapy (LLLT) on arthritis‐induced model. Arthritis was induced in C57BL/6 mice divided into five groups: euthanized 5 hours after inflammation induction; untreated; dexamethasone treated; LLLT at 3 Jcm^?2; LLLT at 30 Jcm^?2. Cytokine measurements by enzyme‐linked immunosorbent assay and mRNA cytokine relative levels by real‐time quantitative polymerase chain reaction were performed with arthritic ankle (IL‐1β, IL‐6, TNF‐α, IL‐10 and TGF‐β). Macrophages, dendritic cells, natural killer cells, lymphocytes CD4⁺, CD8⁺, Treg and costimulatory proteins were quantified in proximal lymph node by flow cytometry. Data showed decrease in all cytokine levels after LLLT and alteration in mRNA relative levels, depending on the energy density used. LLLT was able to increase of immune cell populations analyzed in the lymph node as well as costimulatory proteins expression on macrophages and dendritic cells. Treg TCD4⁺ and TCD8⁺ population enrichment were observed in LLLT at 3 and 30 Jcm^?2 groups, respectively. Furthermore, Treg TCD8⁺ cells expressing higher levels of CD25 were observed at LLLT at 30 Jcm^?2 group. Our results indicate that LLLT could change the inflammatory course of arthritis, tending to accelerate its resolution through immune cells photobiostimulation.