RESUMO
Millions of T cells are produced in the thymus, each expressing a unique alpha/beta T cell receptor (TCR) capable of binding to a foreign peptide in the binding groove of a host major histocompatibility complex (MHC) molecule. T cell-mediated immunity to infection is due to the proliferation and differentiation of rare clones in the preimmune repertoire that by chance express TCRs specific for peptide-MHC (pMHC) ligands derived from the microorganism. Here we review recent findings that have altered our understanding of how the preimmune repertoire is established. Recent structural studies indicate that a germline-encoded tendency of TCRs to bind MHC molecules contributes to the MHC bias of T cell repertoires. It has also become clear that the preimmune repertoire contains functionally heterogeneous subsets including recent thymic emigrants, mature naive phenotype cells, memory phenotype cells, and natural regulatory T cells. In addition, sensitive new detection methods have revealed that the repertoire of naive phenotype T cells consists of distinct pMHC-specific populations that consistently vary in size in different individuals. The implications of these new findings for the clonal selection theory, self-tolerance, and immunodominance are discussed.
Assuntos
Complexo Principal de Histocompatibilidade/imunologia , Peptídeos/imunologia , Linfócitos T/imunologia , Animais , Humanos , Ligantes , Receptores de Antígenos de Linfócitos T/imunologia , Timo/imunologiaRESUMO
Human tumors with exonuclease domain mutations in the gene encoding DNA polymerase ε (POLE) have incredibly high mutation burdens. These errors arise in four unique mutation signatures occurring in different relative amounts, the etiologies of which remain poorly understood. We used CRISPR-Cas9 to engineer human cell lines expressing POLE tumor variants, with and without mismatch repair (MMR). Whole-exome sequencing of these cells after defined numbers of population doublings permitted analysis of nascent mutation accumulation. Unlike an exonuclease active site mutant that we previously characterized, POLE cancer mutants readily drive signature mutagenesis in the presence of functional MMR. Comparison of cell line and human patient data suggests that the relative abundance of mutation signatures partitions POLE tumors into distinct subgroups dependent on the nature of the POLE allele, its expression level, and MMR status. These results suggest that different POLE mutants have previously unappreciated differences in replication fidelity and mutagenesis.
Assuntos
Reparo de Erro de Pareamento de DNA/genética , DNA Polimerase II/genética , DNA Polimerase II/metabolismo , Alelos , Linhagem Celular Tumoral , Reparo de Erro de Pareamento de DNA/fisiologia , Humanos , Mutagênese/genética , Mutação/genética , Neoplasias/genética , Neoplasias/metabolismo , Proteínas de Ligação a Poli-ADP-Ribose/genética , Proteínas de Ligação a Poli-ADP-Ribose/metabolismoRESUMO
Adjuvants are often essential additions to vaccines that enhance the activation of innate immune cells, leading to more potent and protective T and B cell responses. Only a few vaccine adjuvants are currently used in approved vaccine formulations in the United States. Combinations of one or more adjuvants have the potential to increase the efficacy of existing and next-generation vaccines. In this study, we investigated how the nontoxic double mutant Escherichia coli heat-labile toxin R192G/L211A (dmLT), when combined with the TLR4 agonist monophosphoryl lipid A (MPL-A), impacted innate and adaptive immune responses to vaccination in mice. We found that the combination of dmLT and MPL-A induced an expansion of Ag-specific, multifaceted Th1/2/17 CD4 T cells higher than that explained by adding responses to either adjuvant alone. Furthermore, we observed more robust activation of primary mouse bone marrow-derived dendritic cells in the combination adjuvant-treated group via engagement of the canonical NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome complex. This was marked by a multiplicative increase in the secretion of active IL-1ß that was independent of classical gasdermin D-mediated pyroptosis. Moreover, the combination adjuvant increased the production of the secondary messengers cAMP and PGE2 in dendritic cells. These results demonstrate how certain adjuvant combinations could be used to potentiate better vaccine responses to combat a variety of pathogens.
Assuntos
Inflamassomos , Vacinas , Animais , Camundongos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Linfócitos T CD4-Positivos , Adjuvantes Imunológicos , Antígenos , Células DendríticasRESUMO
COVID-19 has had an unprecedented global impact on human health. Understanding the Ab memory responses to infection is one tool needed to effectively control the pandemic. Among 173 outpatients who had virologically confirmed SARS-CoV-2 infection, we evaluated serum Ab concentrations, microneutralization activity, and enumerated SARS-CoV-2-specific B cells in convalescent human blood specimens. Serum Ab concentrations were variable, allowing for stratification of the cohort into high and low responders. Neither participant sex, the timing of blood sampling following the onset of illness, nor the number of SARS-CoV-2 spike protein-specific B cells correlated with serum Ab concentration. Serum Ab concentration was positively associated with microneutralization activity and participant age, with participants under the age of 30 showing the lowest Ab level. These data suggest that young adult outpatients did not generate as robust Ab memory, compared with older adults. Body mass index was also positively correlated with serum Ab levels. Multivariate analyses showed that participant age and body mass index were independently associated with Ab levels. These findings have direct implications for public health policy and current vaccine efforts. Knowledge gained regarding Ab memory following infection will inform the need for vaccination in those previously infected and allow for a better approximation of population-wide protective immunity.
Assuntos
Fatores Etários , Formação de Anticorpos , Índice de Massa Corporal , COVID-19 , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Linfócitos B/imunologia , COVID-19/imunologia , Humanos , Pacientes Ambulatoriais , SARS-CoV-2 , Glicoproteína da Espícula de Coronavírus/imunologiaRESUMO
Helminths are distinct from microbial pathogens in both size and complexity, and are the likely evolutionary driving force for type 2 immunity. CD4+ helper T cells can both coordinate worm clearance and prevent immunopathology, but issues of T cell antigen specificity in the context of helminth-induced Th2 and T regulatory cell (Treg) responses have not been addressed. Herein, we generated a novel transgenic line of the gastrointestinal nematode Strongyloides ratti expressing the immunodominant CD4+ T cell epitope 2W1S as a fusion protein with green fluorescent protein (GFP) and FLAG peptide in order to track and study helminth-specific CD4+ T cells. C57BL/6 mice infected with this stable transgenic line (termed Hulk) underwent a dose-dependent expansion of activated CD44hiCD11ahi 2W1S-specific CD4+ T cells, preferentially in the lung parenchyma. Transcriptional profiling of 2W1S-specific CD4+ T cells isolated from mice infected with either Hulk or the enteric bacterial pathogen Salmonella expressing 2W1S revealed that pathogen context exerted a dominant influence over CD4+ T cell phenotype. Interestingly, Hulk-elicited 2W1S-specific CD4+ T cells exhibited both Th2 and Treg phenotypes and expressed high levels of the EGFR ligand amphiregulin, which differed greatly from the phenotype of 2W1S-specific CD4+ T cells elicited by 2W1S-expressing Salmonella. While immunization with 2W1S peptide did not enhance clearance of Hulk infection, immunization did increase total amphiregulin production as well as the number of amphiregulin-expressing CD3+ cells in the lung following Hulk infection. Altogether, this new model system elucidates effector as well as immunosuppressive and wound reparative roles of helminth-specific CD4+ T cells. This report establishes a new resource for studying the nature and function of helminth-specific T cells.
Assuntos
Epitopos de Linfócito T/genética , Estrongiloidíase/imunologia , Linfócitos T Reguladores/imunologia , Células Th2/imunologia , Animais , Animais Geneticamente Modificados , Antígenos de Helmintos , Linfócitos T CD4-Positivos/imunologia , Modelos Animais de Doenças , Epitopos de Linfócito T/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Strongyloides ratti/imunologiaRESUMO
The intracellular bacterial pathogen Salmonella is able to evade the immune system and persist within the host. In some cases, these persistent infections are asymptomatic for long periods and represent a significant public health hazard because the hosts are potential chronic carriers, yet the mechanisms that control persistence are incompletely understood. Using a mouse model of chronic typhoid fever combined with major histocompatibility complex (MHC) class II tetramers to interrogate endogenous, Salmonella-specific CD4+ helper T cells, we show that certain host microenvironments may favorably contribute to a pathogen's ability to persist in vivo We demonstrate that the environment in the hepatobiliary system may contribute to the persistence of Salmonella enterica subsp. enterica serovar Typhimurium through liver-resident immunoregulatory CD4+ helper T cells, alternatively activated macrophages, and impaired bactericidal activity. This contrasts with lymphoid organs, such as the spleen and mesenteric lymph nodes, where these same cells appear to have a greater capacity for bacterial killing, which may contribute to control of bacteria in these organs. We also found that, following an extended period of infection of more than 2 years, the liver appeared to be the only site that harbored Salmonella bacteria. This work establishes a potential role for nonlymphoid organ immunity in regulating chronic bacterial infections and provides further evidence for the hepatobiliary system as the site of chronic Salmonella infection.
Assuntos
Interações Hospedeiro-Patógeno/imunologia , Fígado/imunologia , Salmonelose Animal/imunologia , Salmonella typhimurium/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Doença Crônica , Técnicas de Cocultura , Fator de Transcrição GATA3/genética , Fator de Transcrição GATA3/imunologia , Vesícula Biliar/imunologia , Vesícula Biliar/microbiologia , Regulação da Expressão Gênica/imunologia , Interações Hospedeiro-Patógeno/genética , Imunidade Inata , Interferon gama/genética , Interferon gama/imunologia , Interleucina-10/genética , Interleucina-10/imunologia , Fígado/microbiologia , Linfonodos/imunologia , Linfonodos/microbiologia , Ativação de Macrófagos , Camundongos , Camundongos Endogâmicos C57BL , Especificidade de Órgãos , Células RAW 264.7 , Salmonelose Animal/genética , Salmonelose Animal/microbiologia , Salmonelose Animal/patologia , Salmonella typhimurium/crescimento & desenvolvimento , Salmonella typhimurium/patogenicidade , Análise de Célula Única , Baço/imunologia , Baço/microbiologia , Linfócitos T Auxiliares-Indutores/microbiologiaRESUMO
Effector (Teff) and regulatory (Treg) T cells produce cytokines that balance immunity and immunopathology at sites of infection. It is not known how this balance is achieved. Here, we show that Treg and Teff cells specific for the same foreign peptide:major histocompatibility complex II (pMHCII) ligand accumulated preferentially in a subcutaneous site injected with the relevant antigen plus an adjuvant. Some of the Treg cells in this site were producing IL-10 12 days after injection, whereas a similar fraction of the Teff cells were producing IFN-gamma. Acute ablation of Treg cells increased the fraction of IFN-gamma-producing Teff cells, indicating that Teff function was limited by the Treg cells. Production of cytokines by both populations was driven by pMHCII presentation by local CD11b(hi) dermal dendritic cells. Therefore, balanced production of microbicidal and suppressive cytokines in inflamed skin is achieved by simultaneous dendritic cell antigen presentation to Teff and Treg cells.
Assuntos
Apresentação de Antígeno/imunologia , Linfócitos T CD4-Positivos/imunologia , Citocinas/biossíntese , Citocinas/imunologia , Células Dendríticas/imunologia , Dermatite/imunologia , Dermatite/metabolismo , Animais , Antígenos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Tecido Linfoide/imunologia , Masculino , CamundongosRESUMO
In primary humoral responses, B-cell lymphoma 6 (Bcl6) is a master regulator of follicular helper T (TFH) cell differentiation; however, its activation mechanisms and role in memory responses remain unclear. Here we demonstrate that survival of CXCR5(+) TFH memory cells, and thus subsequent recall antibody response, require Bcl6 expression. Furthermore, we show that, upon rechallenge with soluble antigen Bcl6 in memory TFH cells is rapidly induced in a dendritic cell-independent manner and that peptide:class II complexes (pMHC) on cognate memory B cells significantly contribute to this induction. Given the previous evidence that antigen-specific B cells residing in the follicles acquire antigens within minutes of injection, our results suggest that memory B cells present antigens to the cognate TFH memory cells, thereby contributing to rapid Bcl6 reexpression and differentiation of the TFH memory cells during humoral memory responses.
Assuntos
Linfócitos B/imunologia , Proteínas de Ligação a DNA/imunologia , Memória Imunológica , Linfócitos T Auxiliares-Indutores/imunologia , Transferência Adotiva , Animais , Apresentação de Antígeno , Linfócitos B/citologia , Linfócitos B/metabolismo , Diferenciação Celular/imunologia , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Imunidade Humoral , Imunoglobulina G/metabolismo , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas Proto-Oncogênicas c-bcl-6 , Receptores CXCR5/metabolismo , Subpopulações de Linfócitos T/citologia , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Linfócitos T Auxiliares-Indutores/citologia , Linfócitos T Auxiliares-Indutores/metabolismoRESUMO
UNLABELLED: Helper T-cell epitope dominance in human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 is not adequately explained by peptide binding to major histocompatibility complex (MHC) proteins. Antigen processing potentially influences epitope dominance, but few, if any, studies have attempted to reconcile the influences of antigen processing and MHC protein binding for all helper T-cell epitopes of an antigen. Epitopes of gp120 identified in both humans and mice occur on the C-terminal flanks of flexible segments that are likely to be proteolytic cleavage sites. In this study, the influence of gp120 conformation on the dominance pattern in gp120 from HIV strain 89.6 was examined in CBA mice, whose MHC class II protein has one of the most well defined peptide-binding preferences. Only one of six dominant epitopes contained the most conserved element of the I-Ak binding motif, an aspartic acid. Destabilization of the gp120 conformation by deletion of single disulfide bonds preferentially enhanced responses to the cryptic I-Ak motif-containing sequences, as reported by T-cell proliferation or cytokine secretion. Conversely, inclusion of CpG in the adjuvant with gp120 enhanced responses to the dominant CD4+ T-cell epitopes. The gp120 destabilization affected secretion of some cytokines more than others, suggesting that antigen conformation could modulate T-cell functions through mechanisms of antigen processing. IMPORTANCE: CD4+ helper T cells play an essential role in protection against HIV and other pathogens. Thus, the sites of helper T-cell recognition, the dominant epitopes, are targets for vaccine design; and the corresponding T cells may provide markers for monitoring infection and immunity. However, T-cell epitopes are difficult to identify and predict. It is also unclear whether CD4+ T cells specific for one epitope are more protective than T cells specific for other epitopes. This work shows that the three-dimensional (3D) structure of an HIV protein partially determines which epitopes are dominant, most likely by controlling the breakdown of HIV into peptides. Moreover, some types of signals from CD4+ T cells are affected by the HIV protein 3D structure; and thus the protectiveness of a particular peptide vaccine could be related to its location in the 3D structure.
Assuntos
Epitopos/química , Epitopos/imunologia , Proteína gp120 do Envelope de HIV/química , Proteína gp120 do Envelope de HIV/imunologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Animais , Epitopos/metabolismo , Feminino , Proteína gp120 do Envelope de HIV/metabolismo , Camundongos Endogâmicos CBA , Ligação Proteica , Conformação Proteica , Estabilidade ProteicaRESUMO
CD4(+) memory-phenotype T cells decline over time when generated in response to acute infections cleared by other components of the immune system. Therefore, it was of interest to assess the stability of CD4(+) T cells during a persistent Salmonella infection, which is typical of persistent phagocytic infections that are controlled by this lymphocyte subset. We found that CD4(+) T cells specific for Salmonella peptide:MHC class II (MHCII) ligands were numerically stable for >1 y after initial oral infection. This stability was associated with peptide:MHCII-driven proliferation by a small number of T cells in the secondary lymphoid organs that harbored bacteria. The persistent population consisted of multifunctional Th1 cells that induced PD-1 and became exhausted when transferred to hosts expressing the specific peptide:MHCII ligand in all parts of the body. Thus, persistent infection of phagocytes produced a CD4(+) T cell population that was stably maintained by low-level peptide:MHCII presentation.
Assuntos
Apresentação de Antígeno/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/microbiologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Fragmentos de Peptídeos/metabolismo , Infecções por Salmonella/imunologia , Sequência de Aminoácidos , Animais , Apresentação de Antígeno/genética , Linfócitos T CD4-Positivos/metabolismo , Sobrevivência Celular/genética , Sobrevivência Celular/imunologia , Modelos Animais de Doenças , Epitopos de Linfócito T/genética , Epitopos de Linfócito T/metabolismo , Feminino , Antígenos de Histocompatibilidade Classe II/imunologia , Humanos , Imunofenotipagem/métodos , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Dados de Sequência Molecular , Fragmentos de Peptídeos/genética , Infecções por Salmonella/metabolismo , Infecções por Salmonella/patologia , Salmonella typhi/imunologiaRESUMO
Salmonella infections affect millions worldwide and remain a significant cause of morbidity and mortality. It is known from mouse studies that CD4 T cells are essential mediators of immunity against Salmonella infection, yet it is not clear whether targeting CD4 T cell responses directly with peptide vaccines against Salmonella can be effective in combating infection. Additionally, it is not known whether T cell responses elicited against Salmonella secreted effector proteins can provide protective immunity against infection. In this study, we investigated both of these possibilities using prime-boost immunization of susceptible mice with a single CD4 T cell peptide epitope from Salmonella secreted effector protein I (SseI), a component of the Salmonella type III secretion system. This immunization conferred significant protection against lethal oral infection, equivalent to that conferred by whole heat-killed Salmonella bacteria. Surprisingly, a well-characterized T cell epitope from the flagellar protein FliC afforded no protection compared to immunization with an irrelevant control peptide. The protective response appeared to be most associated with polyfunctional CD4 T cells raised against the SseI peptide, since no antibodies were produced against any of the peptides and very little CD8 T cell response was observed. Overall, this study demonstrates that eliciting CD4 T cell responses against components of the Salmonella type III secretion system can contribute to protection against infection and should be considered in the design of future Salmonella subunit vaccines.
Assuntos
Sistemas de Secreção Bacterianos/imunologia , Linfócitos T CD4-Positivos/imunologia , Infecções por Salmonella/prevenção & controle , Salmonella typhimurium/imunologia , Vacinação/métodos , Animais , Citocinas/metabolismo , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Epitopos de Linfócito T/imunologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Pathogens can substantially alter gene expression within an infected host depending on metabolic or virulence requirements in different tissues, however, the effect of these alterations on host immunity are unclear. Here we visualized multiple CD4 T cell responses to temporally expressed proteins in Salmonella-infected mice. Flagellin-specific CD4 T cells expanded and contracted early, differentiated into Th1 and Th17 lineages, and were enriched in mucosal tissues after oral infection. In contrast, CD4 T cells responding to Salmonella Type-III Secretion System (TTSS) effectors steadily accumulated until bacterial clearance was achieved, primarily differentiated into Th1 cells, and were predominantly detected in systemic tissues. Thus, pathogen regulation of antigen expression plays a major role in orchestrating the expansion, differentiation, and location of antigen-specific CD4 T cells in vivo.
Assuntos
Proteínas de Bactérias/imunologia , Linfócitos T CD4-Positivos/imunologia , Salmonelose Animal/imunologia , Salmonella typhimurium/imunologia , Células Th17/imunologia , Animais , Antígenos de Bactérias/imunologia , Proteínas de Bactérias/metabolismo , Sistemas de Secreção Bacterianos , Linfócitos T CD4-Positivos/microbiologia , Diferenciação Celular/imunologia , Epitopos/análise , Epitopos/imunologia , Flagelina/imunologia , Flagelina/metabolismo , Regulação Bacteriana da Expressão Gênica/imunologia , Interações Hospedeiro-Patógeno , Camundongos , Camundongos Endogâmicos C57BL , Salmonelose Animal/microbiologia , Salmonella typhimurium/patogenicidade , Células Th1/imunologia , Células Th1/microbiologia , Células Th17/microbiologiaRESUMO
Tularemia is caused by subspecies of Francisella tularensis and can manifest in a variety of disease states, with the pneumonic presentation resulting in the greatest mortality. Despite decades of research, there are no approved vaccines against F. tularensis in the United States. Traditional vaccination strategies, such as live-attenuated or subunit vaccines, are not favorable due to inadequate protection or safety concerns. Because of this, novel vaccination strategies are needed to combat tularemia. Here we discuss the current state of and challenges to the tularemia vaccine field and suggest novel vaccine approaches going forward that might be better suited for protecting against F. tularensis infection.
Assuntos
Francisella tularensis , Tularemia , Humanos , Tularemia/prevenção & controle , Vacinas Bacterianas/uso terapêutico , Vacinas Atenuadas , VacinaçãoRESUMO
The SARS-CoV-2 pandemic has highlighted the need for improved vaccines that can elicit long-lasting mucosal immunity. Although mucosal delivery of vaccines represents a plausible method to enhance mucosal immunity, recent studies utilizing intradermal vaccine delivery or incorporation of unique adjuvants suggest that mucosal immunity may be achieved by vaccination via non-mucosal routes. In this expert insight, we highlight emerging evidence from pre-clinical studies that warrant further mechanistic investigation to improve next-generation vaccines against mucosal pathogens, especially those with pandemic potential.
RESUMO
Bordetella spp. are respiratory pathogens equipped with immune evasion mechanisms. We previously characterized a Bordetella bronchiseptica mutant (RB50ΔbtrS) that fails to suppress host responses, leading to rapid clearance and long-lasting immunity against reinfection. This work revealed eosinophils as an exclusive requirement for RB50ΔbtrS clearance. We also show that RB50ΔbtrS promotes eosinophil-mediated B/T cell recruitment and inducible bronchus-associated lymphoid tissue (iBALT) formation, with eosinophils being present throughout iBALT for Th17 and immunoglobulin A (IgA) responses. Finally, we provide evidence that XCL1 is critical for iBALT formation but not maintenance, proposing a novel role for eosinophils as facilitators of adaptive immunity against B. bronchiseptica. RB50ΔbtrS being incapable of suppressing eosinophil effector functions illuminates active, bacterial targeting of eosinophils to achieve successful persistence and reinfection. Overall, our discoveries contribute to understanding cellular mechanisms for use in future vaccines and therapies against Bordetella spp. and extension to other mucosal pathogens.
Assuntos
Infecções por Bordetella , Bordetella bronchiseptica , Bordetella , Humanos , Eosinófilos , Infecções por Bordetella/microbiologia , Infecções por Bordetella/prevenção & controle , ReinfecçãoRESUMO
Although most pathogens infect the human body via mucosal surfaces, very few injectable vaccines can specifically target immune cells to these tissues where their effector functions would be most desirable. We have previously shown that certain adjuvants can program vaccine-specific helper T cells to migrate to the gut, even when the vaccine is delivered non-mucosally. It is not known whether this is true for antigen-specific B cell responses. Here we show that a single intradermal vaccination with the adjuvant double mutant heat-labile toxin (dmLT) induces a robust endogenous, vaccine-specific, isotype-switched B cell response. When the vaccine was intradermally boosted, we detected non-circulating vaccine-specific B cell responses in the lamina propria of the large intestines, Peyer's patches, and lungs. When compared to the TLR9 ligand adjuvant CpG, only dmLT was able to drive the establishment of isotype-switched resident B cells in these mucosal tissues, even when the dmLT-adjuvanted vaccine was administered non-mucosally. Further, we found that the transcription factor Batf3 was important for the full germinal center reaction, isotype switching, and Peyer's patch migration of these B cells. Collectively, these data indicate that specific adjuvants can promote mucosal homing and the establishment of activated, antigen-specific B cells in mucosal tissues, even when these adjuvants are delivered by a non-mucosal route. These findings could fundamentally change the way future vaccines are formulated and delivered.
RESUMO
Inflamed skin contains CD4 T-cell subsets that express chemokine receptors CCR4, CCR6, and/or CCR10. Prior attempts to reveal the distinct role(s) of each receptor in T-cell trafficking to skin have not produced a coherent story. Different conclusions drawn by separate research groups are difficult to reconcile because of the disparate inflammation models used. Here we directly compare CD4 T cells from wild-type, CCR4(-/-), CCR6(-/-), and CCR10(-/-) mice in parallel assays of trafficking to skin. Our models require direct competition between wild-type and receptor-deficient populations for access to inflamed cutaneous sites. Major histocompatibility complex-peptide tetramers allowed us to identify antigen-specific endogenous long-term memory CD4 T cells within skin after multiple topical immunizations. We separately analyzed cells from the dermal and epidermal layers, allowing us to assess the involvement of each receptor in trafficking between dermis and epidermis. We found that CCR4 deficiency reduces accumulation of memory CD4 T cells in skin by approximately 20-fold, but neither CCR6 nor CCR10 deficiency yielded any detectable effects. Strikingly, no differences in dermal versus epidermal localization were observed for cells lacking any of these three receptors. Our findings raise the possibility that CCR6 and CCR10 play (as yet) unknown roles in cutaneous T-cell immunology, unrelated to skin-specific trafficking.
Assuntos
Movimento Celular/imunologia , Epiderme/patologia , Receptores de Quimiocinas/metabolismo , Linfócitos T/patologia , Animais , Antígenos CD4/metabolismo , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/efeitos da radiação , Movimento Celular/efeitos da radiação , Derme/efeitos dos fármacos , Derme/patologia , Derme/efeitos da radiação , Epiderme/imunologia , Epiderme/efeitos da radiação , Epitopos/imunologia , Citometria de Fluxo , Antígenos de Histocompatibilidade/imunologia , Memória Imunológica/imunologia , Memória Imunológica/efeitos da radiação , Camundongos , Camundongos Endogâmicos C57BL , Peptídeos/química , Peptídeos/imunologia , Receptores de Antígenos de Linfócitos T/metabolismo , Luz Solar , Linfócitos T/imunologia , Linfócitos T/efeitos da radiaçãoRESUMO
The Foxp3-expressing subset of regulatory CD4(+) T cells have defined Ag specificity and play essential roles in maintaining peripheral tolerance by suppressing the activation of self-reactive T cells. Similarly, during chronic infection, pathogen-specific Foxp3-expressing CD4(+) T cells expand and actively suppress pathogen-specific effector T cells. Herein, we used MHC class II tetramers and Foxp3(gfp) knockin mice to track the kinetics and magnitude whereby pathogen-specific Foxp3(+)CD4(+) and Foxp3(-)CD4(+) cells are primed and expand after acute infection with recombinant Listeria monocytogenes (Lm) expressing the non-"self"-Ag 2W1S(52-68). We demonstrate that Lm infection selectively primes proliferation, expansion, and subsequent contraction of Lm-specific Foxp3(-) effector CD4(+) cells, while the numbers of Lm-specific Foxp3(+)CD4(+) regulatory cells remain essentially unchanged. In sharp contrast, purified 2W1S(52-68) peptide primes coordinated expansion of both Foxp3(+) regulatory and Foxp3(-) effector T cells with the same Ag specificity. Taken together, these results indicate selective priming and expansion of Foxp3(-) CD4 T cells is a distinguishing feature for acute bacterial infection.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/patologia , Diferenciação Celular/imunologia , Epitopos de Linfócito T/imunologia , Fatores de Transcrição Forkhead/deficiência , Fatores de Transcrição Forkhead/genética , Listeriose/imunologia , Listeriose/patologia , Ativação Linfocitária/imunologia , Sequência de Aminoácidos , Animais , Contagem de Linfócito CD4 , Linfócitos T CD4-Positivos/microbiologia , Diferenciação Celular/genética , Fatores de Transcrição Forkhead/biossíntese , Técnicas de Introdução de Genes , Antígenos de Histocompatibilidade Classe II/biossíntese , Antígenos de Histocompatibilidade Classe II/química , Antígenos de Histocompatibilidade Classe II/genética , Listeriose/genética , Ativação Linfocitária/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Dados de Sequência Molecular , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/microbiologia , Linfócitos T Reguladores/patologiaRESUMO
Discovery and development of novel adjuvants that can improve existing or next generation vaccine platforms have received considerable interest in recent years. In particular, adjuvants that can elicit both humoral and cellular immune responses would be particularly advantageous because the majority of licensed vaccines are formulated with aluminum hydroxide (alum) which predominantly promotes antibodies. We previously demonstrated that bacterial-derived outer membrane vesicles (OMV) possess inherent adjuvanticity and drive antigen-specific antibody and cellular immune responses to OMV components. Here, we investigated the ability of OMVs to stimulate innate and adaptive immunity and to function as a stand-alone adjuvant. We show that OMVs are more potent than heat-inactivated and live-attenuated bacteria in driving dendritic cell activation in vitro and in vivo. Mice immunized with OMVs admixed with heterologous peptides generated peptide-specific CD4 and CD8 T cells responses. Notably, OMV adjuvant induced much greater antibody and B cell responses to co-delivered ovalbumin compared to the responses elicited by the adjuvants alum and CpG DNA. Additionally, pre-existing antibodies raised against the OMVs did not impair OMV adjuvanticity upon repeat immunization. These results indicate that vaccines adjuvanted with OMVs elicit robust cellular and humoral immune responses, supporting further development of OMV adjuvant for use in next-generation vaccines.
RESUMO
Mast cells are potent mediators of allergy and asthma, yet their role in regulating adaptive immunity remains ambiguous. On the surface of mast cells, the crosslinking of IgE bound to FcεRI by a specific antigen recognized by that IgE triggers the release of immune mediators such as histamine and cytokines capable of activating other immune cells; however, little is known about the mast cell contribution to the induction of endogenous, antigen-specific CD4+ T cells. Here we examined the effects of specific mast cell activation in vivo on the initiation of an antigen-specific CD4+ T cell response. While CD4+ T cells were not enhanced by FcεRI stimulation alone, their activation was synergistically enhanced when FcεRI activation was combined with TLR4 stimulation. This enhanced activation was dependent on global TLR4 stimulation but appeared to be less dependent on mast cell expressed TLR4. This study provides important new evidence to support the role of mast cells as mediators of the antigen-specific adaptive immune response.