RESUMO
Understanding immune responses to SARS-CoV-2 messenger RNA (mRNA) vaccines is of great interest, principally because of the poor knowledge about the mechanisms of protection. In the present study, we analyzed longitudinally B cell and T cell memory programs against the spike (S) protein derived from ancestral SARS-CoV-2 (Wuhan-1), B.1.351 (beta), B.1.617.2 (delta) and B.1.1.529 (omicron) variants of concern (VOCs) after immunization with an mRNA-based vaccine (Pfizer). According to the magnitude of humoral responses 3 months after the first dose, we identified high and low responders. Opposite to low responders, high responders were characterized by enhanced antibody-neutralizing activity, increased frequency of central memory T cells and durable S-specific CD8+ T cell responses. Reduced binding antibodies titers combined with long-term specific memory T cells that had distinct polyreactive properties were found associated with subsequent breakthrough with VOCs in low responders. These results have important implications for the design of new vaccines and new strategies for booster follow-up.
Assuntos
COVID-19 , Vacinas Virais , Anticorpos Neutralizantes , Anticorpos Antivirais , Linfócitos T CD8-Positivos , COVID-19/prevenção & controle , Humanos , RNA Mensageiro/genética , SARS-CoV-2 , VacinaçãoRESUMO
Following antigen recognition, CD8+ T lymphocytes can follow different patterns of differentiation, with the generation of different subsets characterized by distinct phenotypes, functions, and migration properties. The changes of transcription factors activity and chromatin structure dynamics drive the functional differentiation and phenotypic heterogeneity of these T cell subsets, which include short-lived effectors, long-term survival of memory, and also dysfunctional exhausted T cells. Recent progress in the field has shed light on the key contribution of chromatin organization to control the T cell fate specification. In fact, the understanding of these processes has important implications for the development of new immunotherapy protocols and to design new vaccination strategies. Here, we review the current understanding of the contribution of chromatin architecture and transcription factor activity orchestrating the gene expression programs guiding the CD8+ T cell subset commitment. We will focus on epigenetic changes, acting sequentially or in combination, which control the transcriptional programs governing T cell plasticity, stability, and memory. New molecular insights into the mechanisms of maintenance of cellular memory and identity, favoring or impeding the reprogramming, will be discussed in the context of T cell memory differentiation in infection and cancer.
Assuntos
Linfócitos T CD8-Positivos , Epigênese Genética , Diferenciação Celular/genética , Cromatina/genética , Cromatina/metabolismo , Humanos , Memória Imunológica , Ativação Linfocitária , Subpopulações de Linfócitos TRESUMO
The initiation of cytotoxic immune responses by dendritic cells (DCs) requires the presentation of antigenic peptides derived from phagocytosed microbes and infected or dead cells to CD8(+) T cells, a process called cross-presentation. Antigen cross-presentation by non-activated DCs, however, is not sufficient for the effective induction of immune responses. Additionally, DCs need to be activated through innate receptors, like Toll-like receptors (TLRs). During DC maturation, cross-presentation efficiency is first upregulated and then turned off. Here we show that during this transient phase of enhanced cross-presentation, phago-lysosome fusion was blocked by the topological re-organization of lysosomes into perinuclear clusters. LPS-induced lysosomal clustering, inhibition of phago-lysosome fusion and enhanced cross-presentation, all required expression of the GTPase Rab34. We conclude that TLR4 engagement induces a Rab34-dependent re-organization of lysosomal distribution that delays antigen degradation to transiently enhance cross-presentation, thereby optimizing the priming of CD8(+) T cell responses against pathogens.
Assuntos
Apresentação de Antígeno/imunologia , Apresentação Cruzada/imunologia , Células Dendríticas/imunologia , Receptor 4 Toll-Like/imunologia , Animais , Antígenos/imunologia , Linfócitos T CD8-Positivos/imunologia , Citotoxicidade Imunológica/imunologia , Feminino , Citometria de Fluxo , Lisossomos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fagossomos/imunologia , RNA Interferente Pequeno , Transfecção , Proteínas rab de Ligação ao GTP/imunologiaRESUMO
The type I interferons are central to a vast array of immunological functions. The production of these immune-modulatory molecules is initiated at the early stages of the innate immune responses and, therefore, plays a dominant role in shaping downstream events in both innate and adaptive immunity. Indeed, the major role of IFN-α/ß is the induction of priming states, relevant for the functional differentiation of T lymphocyte subsets. Among T-cell subtypes, the CD4+CD25+Foxp3+ T regulatory cells (Tregs) represent a specialized subset of CD4+ T cells with a critical role in maintaining peripheral tolerance and immune homeostasis. Although the role of type I interferons in maintaining the function of thymus-derived Tregs has been previously described, the direct contribution of these innate factors to peripheral Treg (pTreg) and induced Treg (iTreg) differentiation and suppressive function is still unclear. We now show that, under tolerogenic conditions, IFN-α/ß play a critical role in antigen-specific and also polyclonal naive CD4+ T-cell conversion into peripheral antigen-specific CD4+CD25+Foxp3+ Tregs and inhibit CD4+ T helper (Th) cell expansion in mice. While type I interferons sustain the expression and the activation of the transcription master regulators Foxp3, Stat3 and Stat5, these innate molecules reciprocally inhibit Th17 cell differentiation. Altogether, these results indicate a new pivotal role of IFN-α/ß on pTreg differentiation and induction of peripheral tolerance, which may have important implications in the therapeutic control of inflammatory disorders, such as of autoimmune diseases.
RESUMO
Regulatory T (Treg) cells limit the onset of effective antitumor immunity, through yet-ill-defined mechanisms. We showed the rejection of established ovalbumin (OVA)-expressing MCA101 tumors required both the adoptive transfer of OVA-specific CD8(+) T cell receptor transgenic T cells (OTI) and the neutralization of Foxp3(+) T cells. In tumor-draining lymph nodes, Foxp3(+) T cell neutralization induced a marked arrest in the migration of OTI T cells, increased numbers of dendritic cells (DCs), and enhanced OTI T cell priming. Using an in vitro cytotoxic assay and two-photon live microscopy after adoptive transfer of DCs, we demonstrated that Foxp3(+) T cells induced the death of DCs in tumor-draining lymph nodes, but not in the absence of tumor. DC death correlated with Foxp3(+) T cell-DC contacts, and it was tumor-antigen and perforin dependent. We conclude that Foxp3(+) T cell-dependent DC death in tumor-draining lymph nodes limits the onset of CD8(+) T cell responses.
Assuntos
Células Dendríticas/metabolismo , Fibrossarcoma/imunologia , Perforina/metabolismo , Subpopulações de Linfócitos T/metabolismo , Linfócitos T Reguladores/metabolismo , Animais , Adesão Celular , Morte Celular , Linhagem Celular Tumoral , Movimento Celular , Células Dendríticas/imunologia , Células Dendríticas/patologia , Feminino , Fibrossarcoma/patologia , Fatores de Transcrição Forkhead/biossíntese , Linfonodos/patologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Transplante de Neoplasias , Perforina/genética , Perforina/imunologia , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/patologia , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/patologiaRESUMO
Cross-presentation by type 1 DCs (cDC1) is critical to induce and sustain antitumoral CD8 T cell responses to model antigens, in various tumor settings. However, the impact of cross-presenting cDC1 and the potential of DC-based therapies in tumors carrying varied levels of bona-fide neoantigens (neoAgs) remain unclear. Here we develop a hypermutated model of non-small cell lung cancer in female mice, encoding genuine MHC-I neoepitopes to study neoAgs-specific CD8 T cell responses in spontaneous settings and upon Flt3L + αCD40 (DC-therapy). We find that cDC1 are required to generate broad CD8 responses against a range of diverse neoAgs. DC-therapy promotes immunogenicity of weaker neoAgs and strongly inhibits the growth of high tumor-mutational burden (TMB) tumors. In contrast, low TMB tumors respond poorly to DC-therapy, generating mild CD8 T cell responses that are not sufficient to block progression. scRNA transcriptional analysis, immune profiling and functional assays unveil the changes induced by DC-therapy in lung tissues, which comprise accumulation of cDC1 with increased immunostimulatory properties and less exhausted effector CD8 T cells. We conclude that boosting cDC1 activity is critical to broaden the diversity of anti-tumoral CD8 T cell responses and to leverage neoAgs content for therapeutic advantage.
Assuntos
Carcinoma Pulmonar de Células não Pequenas , Neoplasias Pulmonares , Feminino , Camundongos , Animais , Células Dendríticas , Carcinoma Pulmonar de Células não Pequenas/terapia , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Neoplasias Pulmonares/terapia , Neoplasias Pulmonares/metabolismo , Linfócitos T CD8-Positivos , Apresentação CruzadaRESUMO
Type I IFNs are central to a vast array of immunological functions. Their early induction in innate immune responses provides one of the most important priming mechanisms for the subsequent establishment of adaptive immunity. The outcome is either promotion or inhibition of these responses, but the conditions under which one or the other prevails remain to be defined. The main objective of the current study was to determine the involvement of IFN-alpha on murine CD4(+)CD25(-) Th cell activation, as well as to define the role played by this cytokine on CD4(+)CD25(+) regulatory T (Treg) cell proliferation and function. Although IFN-alpha promotes CD4(+)CD25(-) Th cells coincubated with APCs to produce large amounts of IL-2, the ability of these cells to respond to IL-2 proliferative effects is prevented. Moreover, in medium supplemented with IFN-alpha, IL-2-induced CD4(+)CD25(+) Treg cell proliferation is inhibited. Notably, IFN-alpha also leads to a decrease of the CD4(+)CD25(+) Treg cell suppressive activity. Altogether, these findings indicate that through a direct effect on APC activation and by affecting CD4(+)CD25(+) Treg cell-mediated suppression, IFN-alpha sustains and drives CD4(+)CD25(-) Th cell activation.
Assuntos
Células Apresentadoras de Antígenos/imunologia , Interferon-alfa/imunologia , Ativação Linfocitária/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Reguladores/imunologia , Animais , Western Blotting , Proliferação de Células , Separação Celular , Células Cultivadas , Técnicas de Cocultura , Feminino , Citometria de Fluxo , Interleucina-2/biossíntese , Interleucina-2/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Receptor de Interferon alfa e beta/imunologiaRESUMO
Single-cell RNA sequencing (sc-RNAseq) has become a critical approach for the analysis of immune cell function and heterogeneity. So far, the immune cell isolation, based on surface marker expression predicted by the RNA expression profiles, is often limited by the poor correlation between transcript and protein expression patterns. To overcome these difficulties, novel single-cell multi-omic approaches based on the combined analysis of transcript and surface protein expression have been developed. One of the major benefits of these technologies is the possibility to use a high number of antibodies conjugated with oligonucleotide (AbOs) for the surface marker detection, thus overcoming the limit of using few surface markers as occurs in flow cytometry. Here we describe the BD Rhapsody single-cell analysis system protocol for 3' mRNA whole transcriptome analysis (WTA), combined with AbO- and Sample Tag library preparation.
Assuntos
Análise de Célula Única , Perfilação da Expressão Gênica , RNA , Análise de Sequência de RNA , TranscriptomaRESUMO
Single-cell multi-omics is a rapidly evolving field, thanks to a fast technological improvement and the growing accuracy of dedicated computational tools for data analysis. Its importance is highlighted by the possibility to distinguish apparently identical cells based on their pattern of gene expression. In this review, the mostly used methodological pipelines for single-cell analysis, as well as the advantages and potential limitations of several analytical steps, are presented and discussed, with specific sections focusing on crucial parts of this procedure, their bioinformatic tools, as well as their advantages and potential drawbacks. The current bioinformatic approaches for T-cell receptor (TCR) reconstruction are also introduced, as well as a comparison of single-cell sequencing technologies. Critical points that may introduce analytical biases and potential inaccuracies in data interpretation are also highlighted.
Assuntos
Biologia Computacional , Análise de Célula Única , Biologia Computacional/métodos , Receptores de Antígenos de Linfócitos T/genética , Análise de Sequência de RNA/métodos , Análise de Célula Única/métodos , Linfócitos TRESUMO
Upon chronic antigen exposure, CD8+ T cells become exhausted, acquiring a dysfunctional state correlated with the inability to control infection or tumor progression. In contrast, stem-like CD8+ T progenitors maintain the ability to promote and sustain effective immunity. Adenovirus (Ad)-vectored vaccines encoding tumor neoantigens have been shown to eradicate large tumors when combined with anti-programmed cell death protein 1 (αPD-1) in murine models; however, the mechanisms and translational potential have not yet been elucidated. Here, we show that gorilla Ad vaccine targeting tumor neoepitopes enhances responses to αPD-1 therapy by improving immunogenicity and antitumor efficacy. Single-cell RNA sequencing demonstrated that the combination of Ad vaccine and αPD-1 increased the number of murine polyfunctional neoantigen-specific CD8+ T cells over αPD-1 monotherapy, with an accumulation of Tcf1+ stem-like progenitors in draining lymph nodes and effector CD8+ T cells in tumors. Combined T cell receptor (TCR) sequencing analysis highlighted a broader spectrum of neoantigen-specific CD8+ T cells upon vaccination compared to αPD-1 monotherapy. The translational relevance of these data is supported by results obtained in the first 12 patients with metastatic deficient mismatch repair (dMMR) tumors vaccinated with an Ad vaccine encoding shared neoantigens. Expansion and diversification of TCRs were observed in post-treatment biopsies of patients with clinical response, as well as an increase in tumor-infiltrating T cells with an effector memory signature. These findings indicate a promising mechanism to overcome resistance to PD-1 blockade by promoting immunogenicity and broadening the spectrum and magnitude of neoantigen-specific T cells infiltrating tumors.
Assuntos
Linfócitos T CD8-Positivos , Neoplasias , Adenoviridae , Animais , Antígenos de Neoplasias/metabolismo , Humanos , Camundongos , Neoplasias/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismoRESUMO
Tumor-infiltrating CD8 + T cells progressively lose functionality and fail to reject tumors. The underlying mechanism and re-programing induced by checkpoint blockers are incompletely understood. We show here that genetic ablation or pharmacological inhibition of histone lysine methyltransferase Suv39h1 delays tumor growth and potentiates tumor rejection by anti-PD-1. In the absence of Suv39h1, anti-PD-1 induces alternative activation pathways allowing survival and differentiation of IFNγ and Granzyme B producing effector cells that express negative checkpoint molecules, but do not reach final exhaustion. Their transcriptional program correlates with that of melanoma patients responding to immune-checkpoint blockade and identifies the emergence of cytolytic-effector tumor-infiltrating lymphocytes as a biomarker of clinical response. Anti-PD-1 favors chromatin opening in loci linked to T-cell activation, memory and pluripotency, but in the absence of Suv39h1, cells acquire accessibility in cytolytic effector loci. Overall, Suv39h1 inhibition enhances anti-tumor immune responses, alone or combined with anti-PD-1, suggesting that Suv39h1 is an "epigenetic checkpoint" for tumor immunity.
Assuntos
Linfócitos T CD8-Positivos , Melanoma , Metiltransferases , Receptor de Morte Celular Programada 1 , Proteínas Repressoras , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Epigênese Genética , Humanos , Ativação Linfocitária , Linfócitos do Interstício Tumoral/imunologia , Linfócitos do Interstício Tumoral/metabolismo , Melanoma/genética , Melanoma/imunologia , Melanoma/terapia , Metiltransferases/antagonistas & inibidores , Metiltransferases/genética , Metiltransferases/imunologia , Metiltransferases/metabolismo , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Receptor de Morte Celular Programada 1/genética , Receptor de Morte Celular Programada 1/imunologia , Receptor de Morte Celular Programada 1/metabolismo , Proteínas Repressoras/antagonistas & inibidores , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismoRESUMO
Immunological memory is a fundamental hallmark of the adaptive immune responses and one of the most relevant aspects of protective immunity. Our understanding of the processes of memory T-cell differentiation and maintenance of long-term immunity is continuously evolving, and recent advances highlight new regulatory networks and chromatin dynamic changes contributing to maintain T-cell identity and impeding the reprogramming of specific T-cell states. Here, the current understanding of the mechanisms that generate the diversity and the heterogeneity of CD8+ T-cell subsets will be discussed, focusing on the temporal and epigenetic mechanisms orchestrating the establishment and maintenance of distinct states of T-cell fate determination and functional commitment.
Assuntos
Linfócitos T CD8-Positivos , Memória Imunológica , Diferenciação Celular , Epigênese Genética , EpigenômicaRESUMO
The changes of transcription factor activity and chromatin dynamics guide functional differentiation of T cell subsets, including commitment to short-lived effectors and long-term survival of memory T cells. Understanding the lineage relationships among the different stages of effector and memory differentiation has profound therapeutic implications for the development of new vaccine and immunotherapy protocols. Here we review the contribution of chromatin architecture to T cell specification, focusing on the interplay between epigenetic changes and transcriptional programs linked to T cell plasticity, commitment and memory. We will also discuss the translational implications of epigenetic control in the context of infections and cancer.
Assuntos
Epigênese Genética/imunologia , Linfócitos T/citologia , Linfócitos T/imunologia , Animais , Cromatina/imunologia , Epigênese Genética/genética , Humanos , Infecções/imunologia , Neoplasias/imunologia , Linfócitos T/metabolismoRESUMO
Knowing the "point of view" of the immune system is essential to understand the characteristic of a pandemic, such as that generated by the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)-2, responsible for the Coronavirus Disease (COVID)-19. In this review, we will discuss the general host/pathogen interactions dictating protective immune response or immunopathology, addressing the role of immunity or immunopathology in influencing the clinical infection outcome, and debate the potential immunoprophylactic and immunotherapy strategies required to fight the virus infection.
Assuntos
COVID-19/imunologia , Sistema Imunitário/fisiologia , Animais , Anticorpos Monoclonais/uso terapêutico , Autoimunidade , Vacinas contra COVID-19 , Interações Hospedeiro-Patógeno , Humanos , Evasão da Resposta Imune , Imunidade , Imunidade Inata , ImunoterapiaRESUMO
BACKGROUND: Age-related epigenetic dysregulations are associated with several diseases, including cancer. The number of stochastic epigenetic mutations (SEM) has been suggested as a biomarker of life-course accumulation of exposure-related DNA damage; however, the predictive role of SEMs in cancer has seldom been investigated. METHODS: A SEM, at a given CpG site, was defined as an extreme outlier of DNA methylation value distribution across individuals. We investigated the association of the total number of SEMs with the risk of eight cancers in 4,497 case-control pairs nested in three prospective cohorts. Furthermore, we investigated whether SEMs were randomly distributed across the genome or enriched in functional genomic regions. RESULTS: In the three-study meta-analysis, the estimated ORs per one-unit increase in log(SEM) from logistic regression models adjusted for age and cancer risk factors were 1.25; 95% confidence interval (CI), 1.11-1.41 for breast cancer, and 1.23; 95% CI, 1.07-1.42 for lung cancer. In the Melbourne Collaborative Cohort Study, the OR for mature B-cell neoplasm was 1.46; 95% CI, 1.25-1.71. Enrichment analyses indicated that SEMs frequently occur in silenced genomic regions and in transcription factor binding sites regulated by EZH2 and SUZ12 (P < 0.0001 and P = 0.0005, respectively): two components of the polycomb repressive complex 2 (PCR2). Finally, we showed that PCR2-specific SEMs are generally more stable over time compared with SEMs occurring in the whole genome. CONCLUSIONS: The number of SEMs is associated with a higher risk of different cancers in prediagnostic blood samples. IMPACT: We identified a candidate biomarker for cancer early detection, and we described a carcinogenesis mechanism involving PCR2 complex proteins worthy of further investigations.
Assuntos
Neoplasias da Mama/genética , Epigênese Genética/genética , Neoplasias Pulmonares/genética , Linfoma Difuso de Grandes Células B/genética , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , MutaçãoRESUMO
BACKGROUND: Single-cell RNA sequencing is essential for investigating cellular heterogeneity and highlighting cell subpopulation-specific signatures. Single-cell sequencing applications have spread from conventional RNA sequencing to epigenomics, e.g., ATAC-seq. Many related algorithms and tools have been developed, but few computational workflows provide analysis flexibility while also achieving functional (i.e., information about the data and the tools used are saved as metadata) and computational reproducibility (i.e., a real image of the computational environment used to generate the data is stored) through a user-friendly environment. FINDINGS: rCASC is a modular workflow providing an integrated analysis environment (from count generation to cell subpopulation identification) exploiting Docker containerization to achieve both functional and computational reproducibility in data analysis. Hence, rCASC provides preprocessing tools to remove low-quality cells and/or specific bias, e.g., cell cycle. Subpopulation discovery can instead be achieved using different clustering techniques based on different distance metrics. Cluster quality is then estimated through the new metric "cell stability score" (CSS), which describes the stability of a cell in a cluster as a consequence of a perturbation induced by removing a random set of cells from the cell population. CSS provides better cluster robustness information than the silhouette metric. Moreover, rCASC's tools can identify cluster-specific gene signatures. CONCLUSIONS: rCASC is a modular workflow with new features that could help researchers define cell subpopulations and detect subpopulation-specific markers. It uses Docker for ease of installation and to achieve a computation-reproducible analysis. A Java GUI is provided to welcome users without computational skills in R.
Assuntos
Análise de Sequência de RNA , Análise de Célula Única , Fluxo de Trabalho , Análise por Conglomerados , Humanos , Leucócitos Mononucleares/metabolismo , SoftwareRESUMO
After priming, naïve CD8+ T lymphocytes establish specific heritable transcription programs that define progression to long-lasting memory cells or to short-lived effector cells. Although lineage specification is critical for protection, it remains unclear how chromatin dynamics contributes to the control of gene expression programs. We explored the role of gene silencing by the histone methyltransferase Suv39h1. In murine CD8+ T cells activated after Listeria monocytogenes infection, Suv39h1-dependent trimethylation of histone H3 lysine 9 controls the expression of a set of stem cell-related memory genes. Single-cell RNA sequencing revealed a defect in silencing of stem/memory genes selectively in Suv39h1-defective T cell effectors. As a result, Suv39h1-defective CD8+ T cells show sustained survival and increased long-term memory reprogramming capacity. Thus, Suv39h1 plays a critical role in marking chromatin to silence stem/memory genes during CD8+ T effector terminal differentiation.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Inativação Gênica , Histona-Lisina N-Metiltransferase/metabolismo , Memória Imunológica , Listeriose/imunologia , Metiltransferases/metabolismo , Proteínas Repressoras/metabolismo , Animais , Diferenciação Celular , Células Cultivadas , Cromatina/metabolismo , Epigênese Genética , Feminino , Histona-Lisina N-Metiltransferase/genética , Histonas/metabolismo , Listeria monocytogenes/imunologia , Masculino , Metilação , Metiltransferases/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Repressoras/genéticaRESUMO
The aim of this study was to evaluate whether daily whole-body exposure to 900 MHz GSM-modulated radiation could affect spleen lymphocytes. C57BL/6 mice were exposed 2 h/day for 1, 2 or 4 weeks in a TEM cell to an SAR of 1 or 2 W/kg. Untreated and sham-exposed groups were also examined. At the end of the exposure, mice were killed humanely and spleen cells were collected. The number of spleen cells, the percentages of B and T cells, and the distribution of T-cell subpopulations (CD4 and CD8) were not altered by the exposure. T and B cells were also stimulated ex vivo using specific monoclonal antibodies or LPS to induce cell proliferation, cytokine production and expression of activation markers. The results did not show relevant differences in either T or B lymphocytes from mice exposed to an SAR of 1 or 2 W/kg and sham-exposed mice with few exceptions. After 1 week of exposure to 1 or 2 W/kg, an increase in IFN-gamma (Ifng) production was observed that was not evident when the exposure was prolonged to 2 or 4 weeks. This suggests that the immune system might have adapted to RF radiation as it does with other stressing agents. All together, our in vivo data indicate that the T- and B-cell compartments were not substantially affected by exposure to RF radiation and that a clinically relevant effect of RF radiation on the immune system is unlikely to occur.