Cytotoxicity of zinc oxide nanoparticles to innate and adaptive human immune cells.

Zinc oxide nanoparticles (ZnO-NPs) are widely used in almost every area of life. Therefore, exposure to them is unavoidable, which makes it necessary to assess their safety for humans. This paper aims to determine toxicity of ZnO-NPs of two diameters toward human immune cells responsible for: innate response (U-937 and HL-60) and acquired response (COLO-720L and HUT-78). Mitochondrial activity, membrane integrity, degree of cellular lipid oxidation, induction of inflammation, and activation of the apoptosis pathway were evaluated to determine differences in cellular response to the tested nanoparticles. ZnO-NPs with a diameter of 100 and 130 nm cause significant cell mortality at 25 and 12 mg/L, respectively. Mitochondrial damage leads to the activation of the caspase cascade and, consequently, to cell apoptosis. ZnO-NPs also cause peroxidation of membrane lipids. Due to the photocatalytic properties of ZnO-NPs, the effect of ultraviolet (UV) irradiation on the degree of their toxicity was also investigated. However, UV irradiation enhances the toxic effect of nanoparticles mainly by weakening the cell's defense capabilities. ZnO-NPs are cytotoxic to human immune system, and they may cause both long-term and short-term negative effects.

Radiation-induced bystander and abscopal effects: important lessons from preclinical models.

Radiotherapy is a pivotal component in the curative treatment of patients with localised cancer and isolated metastasis, as well as being used as a palliative strategy for patients with disseminated disease. The clinical efficacy of radiotherapy has traditionally been attributed to the local effects of ionising radiation, which induces cell death by directly and indirectly inducing DNA damage, but substantial work has uncovered an unexpected and dual relationship between tumour irradiation and the host immune system. In clinical practice, it is, therefore, tempting to tailor immunotherapies with radiotherapy in order to synergise innate and adaptive immunity against cancer cells, as well as to bypass immune tolerance and exhaustion, with the aim of facilitating tumour regression. However, our understanding of how radiation impacts on immune system activation is still in its early stages, and concerns and challenges regarding therapeutic applications still need to be overcome. With the increasing use of immunotherapy and its common combination with ionising radiation, this review briefly delineates current knowledge about the non-targeted effects of radiotherapy, and aims to provide insights, at the preclinical level, into the mechanisms that are involved with the potential to yield clinically relevant combinatorial approaches of radiotherapy and immunotherapy.

Sunscreen applied at ≥ 2 mg cm-2 during a sunny holiday prevents erythema, a biomarker of ultraviolet radiation-induced DNA damage and suppression of acquired immunity.

BACKGROUND: Sun protection factor (SPF) is assessed with sunscreen applied at 2 mg cm-2 . People typically apply around 0·8 mg cm-2 and use sunscreen daily for holidays. Such use results in erythema, which is a risk factor for skin cancer. OBJECTIVES: To determine (i) whether typical sunscreen use resulted in erythema, epidermal DNA damage and photoimmunosuppression during a sunny holiday, (ii) whether optimal sunscreen use inhibited erythema and (iii) whether erythema is a biomarker for photoimmunosuppression in a laboratory study. METHODS: Holidaymakers (n = 22) spent a week in Tenerife (very high ultraviolet index) using their own sunscreens without instruction (typical sunscreen use). Others (n = 40) were given SPF 15 sunscreens with instructions on how to achieve the labelled SPF (sunscreen intervention). Personal ultraviolet radiation (UVR) exposure was monitored electronically as the standard erythemal dose (SED) and erythema was quantified. Epidermal cyclobutane pyrimidine dimers (CPDs) were determined by immunostaining, and immunosuppression was assessed by contact hypersensitivity (CHS) response. RESULTS: There was no difference between personal UVR exposure in the typical sunscreen use and sunscreen intervention groups (P = 0·08). The former had daily erythema on five UVR-exposed body sites, increased CPDs (P < 0·001) and complete CHS suppression (20 of 22). In comparison, erythema was virtually absent (P < 0·001) when sunscreens were used at ≥ 2 mg cm-2 . A laboratory study showed that 3 SED from three very different spectra suppressed CHS by around ~50%. CONCLUSIONS: Optimal sunscreen use prevents erythema during a sunny holiday. Erythema predicts suppression of CHS (implying a shared action spectrum). Given that erythema and CPDs share action spectra, the data strongly suggest that optimal sunscreen use will also reduce CPD formation and UVR-induced immunosuppression.

A review on the effects of extremely low frequency electromagnetic field (ELF-EMF) on cytokines of innate and adaptive immunity.

Extremely low frequency electromagnetic field (ELF-EMF) is produced extensively in modern technologies. Numerous in vitro and in vivo studies have shown that ELF-EMF has both stimulatory and inhibitory effects on the immune system response. This review was conducted on effects of ELF-EMF on cytokines of innate and adaptive immunity. Mechanisms of ELF-EMF, which may modulate immune cell responses, were also studied. Physical and biological parameters of ELF-EMF can interact with each other to create beneficial or harmful effect on the immune cell responses by interfering with the inflammatory or anti-inflammatory cytokines. According to the studies, it is supposed that short-term (2-24 h/d up to a week) exposure of ELF-EMF with strong density may increase innate immune response due to an increase of innate immunity cytokines. Furthermore, long-term (2-24 h/d up to 8 years) exposure to low-density ELF-EMF may cause a decrease in adaptive immune response, especially in Th1 subset.

Daily very low UV dose exposure enhances adaptive immunity, compared with a single high-dose exposure. Consequences for the control of a skin infection.

Ultraviolet radiation (UVr) promotes several well-known molecular changes, which may ultimately impact on health. Some of these effects are detrimental, like inflammation, carcinogenesis and immunosuppression. On the other hand, UVr also promotes vitamin D synthesis and other beneficial effects. We recently demonstrated that exposure to very low doses of UVr on four consecutive days [repetitive low UVd (rlUVd)] does not promote an inflammatory state, nor the recruitment of neutrophils or lymphocytes, as the exposure to a single high UV dose (shUVd) does. Moreover, rlUVd reinforce the epithelium by increasing antimicrobial peptides transcription and epidermal thickness. The aim of this study was to evaluate the adaptive immune response after shUVd and rlUVd, determining T-cell and B-cell responses. Finally, we challenged animals exposed to both irradiation procedures with Staphylococcus aureus to study the overall effects of both innate and adaptive immunity during a cutaneous infection. We observed, as expected, a marked suppression of T-cell and B-cell responses after exposure to an shUVd but a novel and significant increase in both specific responses after exposure to rlUVd. However, the control of the cutaneous S. aureus infection was defective in this last group, suggesting that responses against pathogens cannot be ruled out from isolated stimuli.

Clinically Relevant Radiation Exposure Differentially Impacts Forms of Cell Death in Human Cells of the Innate and Adaptive Immune System.

In cancer treatments, especially high-dose radiotherapy (HDRT) is applied. Patients suffering from chronic inflammatory diseases benefit from low-dose radiation therapy (LDRT), but exposure to very low radiation doses can still steadily increase for diagnostic purposes. Yet, little is known about how radiation impacts on forms of cell death in human immune cells. In this study, the radiosensitivity of human immune cells of the peripheral blood was examined in a dose range from 0.01 to 60 Gy with regard to induction of apoptosis, primary necrosis, and secondary necrosis. Results showed that immune cells differed in their radiosensitivity, with monocytes being the most radioresistant. T cells mainly died by necrosis and were moderately radiosensitive. This was followed by B and natural killer (NK) cells, which died mainly by apoptosis. X-radiation had no impact on cell death in immune cells at very low doses (≤0.1 Gy). Radiation doses of LDRT (0.3⁻0.7 Gy) impacted on the more radiosensitive NK and B cells, which might contribute to attenuation of inflammation. Even single doses applied during RT of tumors did not erase the immune cells completely. These in vitro studies can be considered as the basis to optimize individual radiation therapy schemes in multimodal settings and to define suited time points for further inclusion of immunotherapies.

Immune checkpoint inhibitors with radiotherapy and locoregional treatment: synergism and potential clinical implications.

PURPOSE OF REVIEW: Antigens recognized by T cells in tumors include differentiation antigens, overexpressed antigens, cancer-testis, and mutated tumor neoantigens. Ionizing radiation causes damage to multiple biomolecules by direct energy deposition or by generation of free radicals, leading to cell death when the damage cannot be repaired. Tumor cell death induced by radiation will generate specific molecular signals that are sensed by antigen-presenting cells and stimulate their maturation and ability to cross-present tumor-derived antigens to T cells. Immunogenic cell death will complement the activity of immune checkpoint inhibitors. We will provide the emerging information coming from preclinical and clinical testing about the combinations of immunotherapies and radiotherapy. RECENT FINDINGS: Radiation induces chemokines that attract effector T cells to the tumor and vascular adhesion molecules that facilitate T-cell infiltration. This process, which has been named 'immunogenic modulation', plays a role not only in regression of the irradiated tumor but also in amplifying and strengthening adaptive antitumor immunity. The ongoing process of killing of tumor cells by cytotoxic T lymphocytes sustains release of more tumor antigens and possibly promotes antigenic spread, that is, activation of a broader T-cell repertoire. Results of several ongoing clinical trials are testing the combination of radiotherapy with immune checkpoint inhibitor treatment. Data support a model whereby 'waves' of tumor cell killing by T cells primed by the initial radiation-elicited antigen release boost the immune response. This process can eventually achieve systemic tumor control. SUMMARY: Radiation therapy is confirmed to be a sensitizer of tumors to immune checkpoint inhibitors in clinical trials, and its application will be easy to implement and widespread. Conversely, many issues need to be addressed before radiotherapy can become such a valid immunogenic tool. An area of increasing importance will be the development of suitable biomarkers that will be able to reliably assess 'immunogenic tumor cell death', immune effector stimulation, and adaptive immunity. Such an immune profile of biomarkers will aid in searching for an optimal combination of radiotherapy and immunomodulation and allows patient selection and response prediction.

The impact of the myeloid response to radiation therapy.

Radiation therapy is showing potential as a partner for immunotherapies in preclinical cancer models and early clinical studies. As has been discussed elsewhere, radiation provides debulking, antigen and adjuvant release, and inflammatory targeting of effector cells to the treatment site, thereby assisting multiple critical checkpoints in antitumor adaptive immunity. Adaptive immunity is terminated by inflammatory resolution, an active process which ensures that inflammatory damage is repaired and tissue function is restored. We discuss how radiation therapy similarly triggers inflammation followed by repair, the consequences to adaptive immune responses in the treatment site, and how the myeloid response to radiation may impact immunotherapies designed to improve control of residual cancer cells.

Photoimmunosuppression: a brief overview.

Exposure to ultraviolet radiation can lead to suppression of many adaptive immune responses, both to antigens encountered within a short period of the irradiation (primary) and to antigens previously encountered (memory). The pathways involved are complex and not completely elucidated. This brief review summarizes the information available currently regarding the multiple steps involved, with the aim of providing a general overview of the main aspects of photoimmunosuppression and its clinical consequences.

Protein extract of ultraviolet-irradiated human skin keratinocytes promote the expression of mitogen-activated protein kinases, nuclear factor-κB and interferon regulatory factor-3 in Langerhans cells via Toll-like receptor 2 and 4.

AIM: In this study, we investigated whether the protein extract of ultraviolet-irradiated human skin keratinocytes can activate Toll-like receptor 2 and Toll-like receptor 4 of Langerhans cells and induce the downstream gene expression of mitogen-activated protein kinases, nuclear factor-κB and interferon regulatory factor-3. METHODS: The protein expression of mitogen-activated protein kinases, nuclear factor-κB and interferon regulatory factor-3 in Langerhans cells and the protein expression of HSP60, HSP70 and ß-defensin 2 in keratinocytes were examined using Western blot analysis. Langerhans cells were pretreated with or without Toll-like receptor 2 and Toll-like receptor 4 siRNA. RESULTS: We found that the protein extract of ultraviolet-irradiated keratinocytes upregulated the expression of mitogen-activated protein kinases, nuclear factor-κB and interferon regulatory factor-3 in Langerhans cells via Toll-like receptor 2 and Toll-like receptor 4. We also found that ultraviolet radiation upregulated the expression HSP60, HSP70 and ß-defensin 2 in keratinocytes. CONCLUSIONS: Our previous study demonstrated that ultraviolet radiation upregulated Toll-like receptor 2 and Toll-like receptor 4 expression in Langerhans cells. Ultraviolet radiation also upregulated mitogen-activated protein kinases and nuclear factor-κB/p65 expression via Toll-like receptor 2 and Toll-like receptor 4, and upregulated interferon regulatory factor-3 expression partially via Toll-like receptor 4. So we conclude that ultraviolet radiation can directly or indirectly activate keratinocytes to induce endogenous ligands which stimulate Toll-like receptor 2- or Toll-like receptor 4-dependent signaling cascade in Langerhans cells, sequentially influence innate and adaptive immune responses.

Innate immunity: Looking beyond T-cells in radiation and immunotherapy combinations.

Radiation therapy is an established and effective anti-cancer treatment modality. Extensive pre-clinical experimentation has demonstrated that the pro-inflammatory properties of irradiation may be synergistic with checkpoint immunotherapy. Radiation induces double-stranded DNA breaks (dsDNA). Sensing of the dsDNA activates the cGAS/STING pathway, producing Type 1 interferons essential to recruiting antigen-presenting cells (APCs). Radiation promotes cytotoxic CD8 T-cell recruitment by releasing tumour-associated antigens captured and cross-presented by surveying antigen-presenting cells. Radiation-induced vascular normalisation may further promote T-cell trafficking and drug delivery. Radiation is also immunosuppressive. Recruitment of regulatory T cells (Tregs) and innate cells such as myeloid-derived suppressive cells (m-MDSCs) all counteract the immunostimulatory properties of radiation. Many innate immune cell types operate at the interface of the adaptive immune response. Innate immune cells, such as m-MDSCs, can exert their immunosuppressive effects by expressing immune checkpoints such as PD-L1, further highlighting the potential of combined radiation and checkpoint immunotherapy. Several early-phase clinical studies investigating the combination of radiation and immunotherapy have been disappointing. A greater appreciation of radiotherapy's impact on the innate immune system is essential to optimise radioimmunotherapy combinations. This review will summarise the impact of radiotherapy on crucial cells of the innate immune system and vital immunosuppressive cytokines.

Treatment with GM-CSF secreting myeloid leukemia cell vaccine prior to autologous-BMT improves the survival of leukemia-challenged mice.

Vaccination with irradiated autologous tumor cells, engineered to secrete granulocyte macrophage-colony stimulating factor (GM-CSF) (GM tumor), can generate potent antitumor effects when combined with autologous bone marrow transplantation (BMT). That notwithstanding, the post-BMT milieu, characterized by marked cytopenia, can pose a challenge to the implementation of vaccine immunotherapies. To bypass this problem, partial post-BMT immune reconstitution has been allowed to develop prior to vaccination. However, delaying vaccination can also potentially allow the expansion of residual tumor cells. Other approaches have used reinfusion of "primed" autologous lymphocytes and multiple administrations of GM tumor cells, which required the processing of large amounts of tumor. Utilizing the MMB3.19 murine myeloid leukemia model, we tested whether a single dose of GM tumor cells, 7 days prior to syngeneic BMT, could be a curative treatment in MMB3.19-challenged recipient mice. This vaccination protocol significantly improved survival of mice by eliciting long-lasting host immune responses that survived lethal irradiation, and were even protective against post-BMT tumor rechallenge. Furthermore, we demonstrated that mature donor lymphocytes can also play a limited role in mounting the antitumor response, but our pre-BMT vaccination strategy obviated the need for either established de novo immune reconstitution or the use of multiple post-BMT immunizations.

Regulatory T Cells Shape the Differential Impact of Radiation Dose-Fractionation Schedules on Host Innate and Adaptive Antitumor Immune Defenses.

PURPOSE: We examined how radiation dose per fraction (DPF) and total dose, as represented by biological effective dose (BED), can independently and differentially affect the immunomodulatory capacity of radiation therapy (RT). METHODS AND MATERIALS: AT3-OVA mammary and MC38 colorectal tumors in C57BL/6 mice were irradiated with rationally selected dose-fractionation schedules, alone or with immune-modulating or -depleting agents. Tumor growth was monitored as a readout of therapeutic response. Flow cytometry and RNA sequencing of mouse tumors and analysis of transcriptomic data sets from irradiated human cancers were used to examine the immunomodulatory effects of the different radiation schedules. RESULTS: In AT3-OVA tumors, radiation DPF rather than BED determined the ability of RT to evoke local antitumor CD8+ T cell responses and synergize with anti-PD-1 therapy. Natural killer cell-mediated control of irradiated tumors was more sensitive to radiation BED. Radiation-induced regulatory T cell (Treg) responses, which were detected in both mouse and human tumors, were a major factor underlying the differential activation of adaptive immunity by radiation DPF and the activity of natural killer cells during the early phase of response to RT. Targeted inhibition of Treg responses within irradiated tumors rescued and enhanced local tumor control by RT and permitted the generation of abscopal and immunologic memory responses, irrespective of radiation schedule. MC38 tumors did not support the induction of an amplified Treg response to RT and were highly vulnerable to its immunoadjuvant effects. CONCLUSIONS: Local radiation-induced Treg responses are influenced by radiation schedule and tumor type and are a critical determinant of the immunoadjuvant potential of RT and its ability to synergize with T cell-targeted immunotherapy.

In vivo study of interferon-γ, transforming growth factor-ß, and interleukin-4 gene expression induced by radioadaptive response.

INTRODUCTION: In the present study, the radioadaptive role of the immune system induced by low dose (LD) was investigated for its in vivo protective activity. MATERIALS AND METHODS: Quantitative analysis of cytokine gene expression was assessed for their in vivo activity in BALB/c mice. To evaluate the adaptive response induced by LD on the mice spleen lymphocyte, the cytokine interleukin (IL)-4, interferon (IFN)-γ, and transforming growth factor (TGF)-ß expression was measured by a real-time quantitative polymerase chain reaction. To verify the radioadaptive effect of LD, animals were preirradiated at 10 cGy from a 60 Co source and then challenge dose at 200 cGy was delivered. Independent sample student's t-test was employed to compare cytokine gene expression in radioadaptive (10 + 200 cGy), LD (10 cGy), high-dose (HD, 200 cGy), and control groups of animals. RESULTS: Following the HD, the cytokine gene expression of IFN-γ, IL-4, and TGF-ß was significantly decreased compared to the control group (P = 0.0001). However, TGF-ß expression was also decreased significantly in the LD and adaptive groups compared to the control group (P = 0.0001). IFN-γ/IL-4 ratio in the adaptive group was significantly decreased compared to the HD group (P = 0.0001). CONCLUSION: These results indicate that the immune system plays an important role for radioadaptive response induction by LD radiation to adjust the harmful effects of HD irradiation.

Ultraviolet radiation, vitamin D, and COVID-19.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has become pandemic on March 11th, 2020. COVID-19 has a range of symptoms that includes fever, fatigue, dry cough, aches, and labored breathing to acute respiratory distress and possibly death. Health systems and hospitals have been completely rearranged since March 2020 in order to limit the high rate of virus spreading. Hence, a great debate on deferrable visits and treatments including phototherapy for skin diseases is developing. In particular, as regards phototherapy very few data are currently available regarding the chance to continue it, even if it may be a useful resource for treating numerous dermatological patients. However, phototherapy has an immunosuppressive action possibly facilitating virus infection. In the context of COVID-19 infection risk it is important to pointed out whether sunlight, phototherapy and in particular ultraviolet radiation (UV-R) constitute or not a risk for patients. In this review we aimed to focus on the relationship between UV-R, sunlight, phototherapy, and viral infections particularly focusing on COVID-19.

Targeting MerTK Enhances Adaptive Immune Responses After Radiation Therapy.

PURPOSE: The role of MerTK, a member of the Tyro3-Axl-MerTK family of receptor tyrosine kinase, in the immune response to radiation therapy (RT) is unclear. We investigated immune-mediated tumor control after RT in murine models of colorectal and pancreatic adenocarcinoma using MerTK wild-type and knock-out hosts and whether inhibition of MerTK signaling with warfarin could replicate MerTK knock-out phenotypes. METHODS AND MATERIALS: Wild-type and MerTK-/- BALB/c mice were grafted in the flanks with CT26 tumors and treated with computed tomography guided RT. The role of macrophages and CD8 T cells in the response to radiation were demonstrated with cell depletion studies. The role of MerTK in priming immune responses after RT alone and with agonist antibodies to the T cell costimulatory molecule OX40 was evaluated in a Panc02-SIY model antigen system. The effect of warfarin therapy on the in-field and abscopal response to RT was demonstrated in murine models of colorectal adenocarcinoma. The association between warfarin and progression-free survival for patients treated with SABR for early-stage non-small cell lung cancer was evaluated in a multi-institutional retrospective study. RESULTS: MerTK-/- hosts had better tumor control after RT compared with wild-type mice in a macrophage and CD8 T cell-dependent manner. MerTK-/- mice showed increased counts of tumor antigen-specific CD8 T cells in the peripheral blood after tumor-directed RT alone and in combination with agonist anti-OX40. Warfarin therapy phenocopied MerTK-/- for single-flank tumors treated with RT and improved abscopal responses for RT combined with anti-CTLA4. Patients on warfarin therapy when treated with SABR for non-small cell lung cancer had higher progression-free survival rates compared with non-warfarin users. CONCLUSIONS: MerTK inhibits adaptive immune responses after SABR. Because warfarin inhibits MerTK signaling and phenocopies genetic deletion of MerTK in mice, warfarin therapy may have beneficial effects in combination with SABR and immune therapy in patients with cancer.

Type I Interferon Response in Radiation-Induced Anti-Tumor Immunity.

The anti-tumor activity of interferons (IFNs) was first appreciated about half a century ago, and IFN-α2 was the first cancer immunotherapy approved by the US Food and Drug Administration. Radiation therapy (RT), one of the pillars of cancer treatment, directly causes DNA damage, which can lead to senescence and cell death in tumor cells. In recent years, however, RT-induced immunomodulatory effects have been recognized to play an indispensable role in achieving the optimum therapeutic effect of RT. Increasing evidence indicates that RT enhances adaptive anti-tumor immunity by augmenting the innate immune sensing of tumors in a type I IFN-dependent matter. This review briefly introduces the role of type I interferon in cancer and the available evidence on the overall effects of RT on tumor immunity mediated via type I IFN. Recent advances in deciphering the molecular mechanisms underlying the induction of type I IFNs triggered by RT, their clinical implications, and therapeutic opportunities will be highlighted.

Effects of Radiation on the Tumor Microenvironment.

A malignant tumor consists of malignant cells as well as a wide array of normal host tissues including stroma, vasculature, and immune infiltrate. The interaction between cancer and these host tissues is critical as these host tissues play a variety of roles in supporting or resisting disease progression. Radiotherapy (RT) has direct effects on malignant cells, but, also, critically important effects on these other components of the tumor microenvironment (TME). Given the growing role of immune checkpoint inhibitors and other immunotherapy strategies, understanding how RT affects the TME, particularly the immune compartment, is essential to advance RT in this new era of cancer therapy. The interactions between RT and the TME are complex, affecting the innate and adaptive arms of the immune system. RT can induce both proinflammatory effects and immune suppressive effects that can either promote or impede antitumor immunity. It is likely that the initial proinflammatory effects of RT eventually lead to rebound immune-suppression as chronic inflammation sets in. The exact kinetics and nature of how RT changes the TME likely depends on timing, dose, fractionation, site irradiated, and tumor type. With increased understanding of the effects of RT on the TME, in the future it is likely that we will be able to personalize RT by varying the dose, site, and timing of intervention to generate the desired response to partner with immunotherapy strategies.

The Impact of Radiation Therapy on Innate and Adaptive Tumor Immunity.

The role of radiation therapy for cancer is evolving as its biologic effects on tumors becomes more clearly defined. Traditionally, radiobiology models dose-response curves based on direct cytocidal effects of radiation on tumor cells. However, a more dynamic picture is emerging of the impact of radiation on the tumor microenvironment and the patient's innate and adaptive immune system. Radiation produces damage associated molecular patterns that activate innate immune receptors leading to a cascade of downstream signals. These signals alter the tumor infiltrating immune population, modulate immune cell activation status, and enhance antigen presentation. The changes are conducive to an adaptive immune response with the generation of antitumor T cells. Early findings from clinical trials incorporating radiation and immune checkpoint inhibitors show promising synergy between the 2 modalities. As more data matures from ongoing trials, clinicians can refine new strategies for using radiation together with immunotherapy to achieve improved clinical outcomes.

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-1ß, IL-6, TNF-α, IL-10 and TGF-ß). 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.