RESUMEN
As central effectors of the adaptive immune response, immunoglobulins, or antibodies, provide essential protection from pathogens through their ability to recognize foreign antigens, aid in neutralization, and facilitate elimination from the host. Mammalian immunoglobulins can be classified into five isotypes-IgA, IgD, IgE, IgG, and IgM-each with distinct roles in mediating various aspects of the immune response. Of these isotypes, IgA and IgM are the only ones capable of multimerization, arming them with unique biological functions. Increased valency of polymeric IgA and IgM provides high avidity for binding low-affinity antigens, and their ability to be transported across the mucosal epithelium into secretions by the polymeric immunoglobulin receptor allows them to play critical roles in mucosal immunity. Here we discuss the molecular assembly, structure, and function of these multimeric antibodies.
Asunto(s)
Inmunoglobulina A , Receptores de Inmunoglobulina Polimérica , Animales , Humanos , Inmunidad Mucosa , Inmunoglobulina M/química , Inmunoglobulina M/metabolismo , Mamíferos/metabolismo , Membrana Mucosa , Receptores de Inmunoglobulina Polimérica/químicaRESUMEN
Among antibodies, IgA is unique because it has evolved to be secreted onto mucosal surfaces. The structure of IgA and the associated secretory component allow IgA to survive the highly proteolytic environment of mucosal surfaces but also substantially limit IgA's ability to activate effector functions on immune cells. Despite these characteristics, IgA is critical for both preventing enteric infections and shaping the local microbiome. IgA's function is determined by a distinct antigen-binding repertoire, composed of antibodies with a variety of specificities, from permissive polyspecificity to cross-reactivity to exquisite specificity to a single epitope, which act together to regulate intestinal bacteria. Development of the unique function and specificities of IgA is shaped by local cues provided by the gut-associated lymphoid tissue, driven by the constantly changing environment of the intestine and microbiota.
Asunto(s)
Inmunidad Mucosa , Inmunoglobulina A , Animales , Humanos , Mucosa Intestinal , Ganglios Linfáticos AgregadosRESUMEN
IgA is the dominant immunoglobulin isotype produced in mammals, largely secreted across the intestinal mucosal surface. Although induction of IgA has been a hallmark feature of microbiota colonization following colonization in germ-free animals, until recently appreciation of the function of IgA in host-microbial mutualism has depended mainly on indirect evidence of alterations in microbiota composition or penetration of microbes in the absence of somatic mutations in IgA (or compensatory IgM). Highly parallel sequencing techniques that enable high-resolution analysis of either microbial consortia or IgA sequence diversity are now giving us new perspectives on selective targeting of microbial taxa and the trajectory of IgA diversification according to induction mechanisms, between different individuals and over time. The prospects are to link the range of diversified IgA clonotypes to specific antigenic functions in modulating the microbiota composition, position and metabolism to ensure host mutualism.
Asunto(s)
Microbioma Gastrointestinal/inmunología , Inmunoglobulina A/inmunología , Mucosa Intestinal/inmunología , Mucosa Intestinal/microbiología , Factores de Edad , Animales , Susceptibilidad a Enfermedades , Interacciones Huésped-Patógeno/inmunología , Humanos , Mucosa Intestinal/metabolismo , Unión ProteicaRESUMEN
The intestinal epithelial barrier includes columnar epithelial, Paneth, goblet, enteroendocrine, and tuft cells as well as other cell populations, all of which contribute properties essential for gastrointestinal homeostasis. The intestinal mucosa is covered by mucin, which contains antimicrobial peptides and secretory IgA and prevents luminal bacteria, fungi, and viruses from stimulating intestinal immune responses. Conversely, the transport of luminal microorganisms-mediated by M, dendritic, and goblet cells-into intestinal tissues facilitates the harmonization of active and quiescent mucosal immune responses. The bacterial population within gut-associated lymphoid tissues creates the intratissue cohabitations for harmonized mucosal immunity. Intermolecular and intercellular communication among epithelial, immune, and mesenchymal cells creates an environment conducive for epithelial regeneration and mucosal healing. This review summarizes the so-called intestinal mucosal ecological network-the complex but vital molecular and cellular interactions of epithelial mesenchymal cells, immune cells, and commensal microbiota that achieve intestinal homeostasis, regeneration, and healing.
Asunto(s)
Células Epiteliales/fisiología , Microbioma Gastrointestinal/inmunología , Mucosa Intestinal/inmunología , Animales , Comunicación Celular , Homeostasis , Humanos , Inmunidad Innata , Inmunoglobulina A/metabolismo , Mucosa Intestinal/patología , Cicatrización de HeridasRESUMEN
Monoclonal antibodies (mAbs) are a focus in vaccine and therapeutic design to counteract severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants. Here, we combined B cell sorting with single-cell VDJ and RNA sequencing (RNA-seq) and mAb structures to characterize B cell responses against SARS-CoV-2. We show that the SARS-CoV-2-specific B cell repertoire consists of transcriptionally distinct B cell populations with cells producing potently neutralizing antibodies (nAbs) localized in two clusters that resemble memory and activated B cells. Cryo-electron microscopy structures of selected nAbs from these two clusters complexed with SARS-CoV-2 spike trimers show recognition of various receptor-binding domain (RBD) epitopes. One of these mAbs, BG10-19, locks the spike trimer in a closed conformation to potently neutralize SARS-CoV-2, the recently arising mutants B.1.1.7 and B.1.351, and SARS-CoV and cross-reacts with heterologous RBDs. Together, our results characterize transcriptional differences among SARS-CoV-2-specific B cells and uncover cross-neutralizing Ab targets that will inform immunogen and therapeutic design against coronaviruses.
Asunto(s)
Anticuerpos Neutralizantes/inmunología , Linfocitos B/metabolismo , SARS-CoV-2/inmunología , Glicoproteína de la Espiga del Coronavirus/inmunología , Anticuerpos Monoclonales/química , Anticuerpos Monoclonales/inmunología , Anticuerpos Neutralizantes/sangre , Anticuerpos Neutralizantes/química , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/química , Anticuerpos Antivirales/inmunología , Complejo Antígeno-Anticuerpo/química , Complejo Antígeno-Anticuerpo/metabolismo , Reacciones Antígeno-Anticuerpo , Linfocitos B/citología , Linfocitos B/virología , COVID-19/patología , COVID-19/virología , Microscopía por Crioelectrón , Cristalografía por Rayos X , Perfilación de la Expresión Génica , Humanos , Inmunoglobulina A/inmunología , Región Variable de Inmunoglobulina/química , Región Variable de Inmunoglobulina/genética , Dominios Proteicos/inmunología , Multimerización de Proteína , Estructura Cuaternaria de Proteína , SARS-CoV-2/aislamiento & purificación , SARS-CoV-2/metabolismo , Análisis de Secuencia de ARN , Glicoproteína de la Espiga del Coronavirus/química , Glicoproteína de la Espiga del Coronavirus/genética , Glicoproteína de la Espiga del Coronavirus/metabolismoRESUMEN
Coronavirus disease 2019 (COVID-19) exhibits variable symptom severity ranging from asymptomatic to life-threatening, yet the relationship between severity and the humoral immune response is poorly understood. We examined antibody responses in 113 COVID-19 patients and found that severe cases resulting in intubation or death exhibited increased inflammatory markers, lymphopenia, pro-inflammatory cytokines, and high anti-receptor binding domain (RBD) antibody levels. Although anti-RBD immunoglobulin G (IgG) levels generally correlated with neutralization titer, quantitation of neutralization potency revealed that high potency was a predictor of survival. In addition to neutralization of wild-type SARS-CoV-2, patient sera were also able to neutralize the recently emerged SARS-CoV-2 mutant D614G, suggesting cross-protection from reinfection by either strain. However, SARS-CoV-2 sera generally lacked cross-neutralization to a highly homologous pre-emergent bat coronavirus, WIV1-CoV, which has not yet crossed the species barrier. These results highlight the importance of neutralizing humoral immunity on disease progression and the need to develop broadly protective interventions to prevent future coronavirus pandemics.
Asunto(s)
Anticuerpos Neutralizantes/inmunología , Biomarcadores/análisis , COVID-19/inmunología , COVID-19/fisiopatología , Adulto , Anticuerpos Neutralizantes/análisis , Anticuerpos Antivirales/análisis , Anticuerpos Antivirales/sangre , Biomarcadores/sangre , COVID-19/sangre , COVID-19/epidemiología , Comorbilidad , Coronavirus/clasificación , Coronavirus/fisiología , Reacciones Cruzadas , Citocinas/sangre , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , Inmunoglobulina A/análisis , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Inmunoglobulina M/sangre , Inmunoglobulina M/inmunología , Masculino , Massachusetts/epidemiología , Persona de Mediana Edad , Dominios Proteicos , SARS-CoV-2/química , SARS-CoV-2/fisiología , Índice de Severidad de la Enfermedad , Glicoproteína de la Espiga del Coronavirus/química , Análisis de Supervivencia , Resultado del TratamientoRESUMEN
Immunoglobulin A (IgA) secretion by plasma cells, terminally differentiated B cells residing in the intestinal lamina propria, assures microbiome homeostasis and protects the host against enteric infections. Exposure to diet-derived and commensal-derived signals provides immune cells with organizing cues that instruct their effector function and dynamically shape intestinal immune responses at the mucosal barrier. Recent data have described metabolic and microbial inputs controlling T cell and innate lymphoid cell activation in the gut; however, whether IgA-secreting lamina propria plasma cells are tuned by local stimuli is completely unknown. Although antibody secretion is considered to be imprinted during B cell differentiation and therefore largely unaffected by environmental changes, a rapid modulation of IgA levels in response to intestinal fluctuations might be beneficial to the host. In the present study, we showed that dietary cholesterol absorption and commensal recognition by duodenal intestinal epithelial cells lead to the production of oxysterols, evolutionarily conserved lipids with immunomodulatory functions. Using conditional cholesterol 25-hydroxylase deleter mouse line we demonstrated that 7α,25-dihydroxycholesterol from epithelial cells is critical to restrain IgA secretion against commensal- and pathogen-derived antigens in the gut. Intestinal plasma cells sense oxysterols via the chemoattractant receptor GPR183 and couple their tissue positioning with IgA secretion. Our findings revealed a new mechanism linking dietary cholesterol and humoral immune responses centered around plasma cell localization for efficient mucosal protection.
Asunto(s)
Inmunidad Innata , Células Plasmáticas , Animales , Ratones , Colesterol en la Dieta , Células Epiteliales , Inmunoglobulina A , Mucosa Intestinal , Receptores Acoplados a Proteínas G , IntestinosRESUMEN
At the species level, immunity depends on the selection and transmission of protective components of the immune system. A microbe-induced population of RORγ-expressing regulatory T cells (Tregs) is essential in controlling gut inflammation. We uncovered a non-genetic, non-epigenetic, non-microbial mode of transmission of their homeostatic setpoint. RORγ+ Treg proportions varied between inbred mouse strains, a trait transmitted by the mother during a tight age window after birth but stable for life, resistant to many microbial or cellular perturbations, then further transferred by females for multiple generations. RORγ+ Treg proportions negatively correlated with IgA production and coating of gut commensals, traits also subject to maternal transmission, in an immunoglobulin- and RORγ+ Treg-dependent manner. We propose a model based on a double-negative feedback loop, vertically transmitted via the entero-mammary axis. This immunologic mode of multi-generational transmission may provide adaptability and modulate the genetic tuning of gut immune responses and inflammatory disease susceptibility.
Asunto(s)
Sistema Digestivo/inmunología , Linfocitos T Reguladores/inmunología , Animales , Susceptibilidad a Enfermedades/inmunología , Femenino , Microbioma Gastrointestinal/inmunología , Homeostasis/inmunología , Inmunoglobulina A/inmunología , Inflamación/inmunología , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Endogámicos CBA , Ratones Endogámicos NOD , Miembro 3 del Grupo F de la Subfamilia 1 de Receptores Nucleares/inmunologíaRESUMEN
Analysis of the specificity and kinetics of neutralizing antibodies (nAbs) elicited by SARS-CoV-2 infection is crucial for understanding immune protection and identifying targets for vaccine design. In a cohort of 647 SARS-CoV-2-infected subjects, we found that both the magnitude of Ab responses to SARS-CoV-2 spike (S) and nucleoprotein and nAb titers correlate with clinical scores. The receptor-binding domain (RBD) is immunodominant and the target of 90% of the neutralizing activity present in SARS-CoV-2 immune sera. Whereas overall RBD-specific serum IgG titers waned with a half-life of 49 days, nAb titers and avidity increased over time for some individuals, consistent with affinity maturation. We structurally defined an RBD antigenic map and serologically quantified serum Abs specific for distinct RBD epitopes leading to the identification of two major receptor-binding motif antigenic sites. Our results explain the immunodominance of the receptor-binding motif and will guide the design of COVID-19 vaccines and therapeutics.
Asunto(s)
Anticuerpos Neutralizantes/inmunología , Mapeo Epitopo/métodos , Glicoproteína de la Espiga del Coronavirus/inmunología , Enzima Convertidora de Angiotensina 2 , Anticuerpos Monoclonales/química , Anticuerpos Monoclonales/genética , Anticuerpos Monoclonales/inmunología , Anticuerpos Neutralizantes/sangre , Anticuerpos Neutralizantes/química , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/química , Anticuerpos Antivirales/inmunología , Reacciones Antígeno-Anticuerpo , Betacoronavirus/inmunología , Betacoronavirus/aislamiento & purificación , Betacoronavirus/metabolismo , Sitios de Unión , COVID-19 , Infecciones por Coronavirus/patología , Infecciones por Coronavirus/virología , Epítopos/química , Epítopos/inmunología , Humanos , Inmunoglobulina A/sangre , Inmunoglobulina A/inmunología , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Inmunoglobulina M/sangre , Inmunoglobulina M/inmunología , Cinética , Simulación de Dinámica Molecular , Pandemias , Peptidil-Dipeptidasa A/química , Peptidil-Dipeptidasa A/metabolismo , Neumonía Viral/patología , Neumonía Viral/virología , Unión Proteica , Dominios Proteicos/inmunología , Estructura Cuaternaria de Proteína , SARS-CoV-2 , Glicoproteína de la Espiga del Coronavirus/química , Glicoproteína de la Espiga del Coronavirus/genética , Glicoproteína de la Espiga del Coronavirus/metabolismoRESUMEN
The urgent need for an effective SARS-CoV-2 vaccine has forced development to progress in the absence of well-defined correlates of immunity. While neutralization has been linked to protection against other pathogens, whether neutralization alone will be sufficient to drive protection against SARS-CoV-2 in the broader population remains unclear. Therefore, to fully define protective humoral immunity, we dissected the early evolution of the humoral response in 193 hospitalized individuals ranging from moderate to severe. Although robust IgM and IgA responses evolved in both survivors and non-survivors with severe disease, non-survivors showed attenuated IgG responses, accompanied by compromised Fcɣ receptor binding and Fc effector activity, pointing to deficient humoral development rather than disease-enhancing humoral immunity. In contrast, individuals with moderate disease exhibited delayed responses that ultimately matured. These data highlight distinct humoral trajectories associated with resolution of SARS-CoV-2 infection and the need for early functional humoral immunity.
Asunto(s)
COVID-19 , Inmunidad Humoral , Inmunoglobulina A/inmunología , Inmunoglobulina M/inmunología , Receptores de IgG/inmunología , SARS-CoV-2/inmunología , COVID-19/inmunología , COVID-19/mortalidad , Femenino , Células HL-60 , Humanos , MasculinoRESUMEN
Durable antibody immunity depends on long-lived plasma cells (LLPCs) that primarily reside in the bone marrow (BM). However, due to LLPC rarity, it has not been possible to define their phenotypes or determine their heterogeneity. By single-cell mRNA sequencing, cytometry and a genetic pulse-chase mouse model, we show that IgG and IgM LLPCs display an EpCAMhiCXCR3- phenotype, whereas IgA LLPCs are Ly6AhiTigit-. While IgG and IgA LLPCs are mainly contributed by somatically hypermutated cells following immunization or infection, cells with innate properties and public antibodies are found in IgA and IgM LLPC compartments. Particularly, IgM LLPCs are highly enriched with public clones shared among different individual animals, differentiated in a T cell-independent manner and have affinity for self-antigens and microbial-derived antigens. Taken together, our work reveals different routes toward LLPC development and paves the way for deeper understanding of cellular and molecular underpinnings of long-term antibody immunity.
Asunto(s)
Microbiota , Células Plasmáticas , Ratones , Animales , Autoantígenos , Inmunización , Inmunoglobulina M , Inmunoglobulina A , Inmunoglobulina GRESUMEN
The first ever US Food and Drug Administration-approved messenger RNA vaccines are highly protective against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)1-3. However, the contribution of each dose to the generation of antibodies against SARS-CoV-2 spike (S) protein and the degree of protection against novel variants warrant further study. Here, we investigated the B cell response to the BNT162b2 vaccine by integrating B cell repertoire analysis with single-cell transcriptomics pre- and post-vaccination. The first vaccine dose elicits a recall response of IgA+ plasmablasts targeting the S subunit S2. Three weeks after the first dose, we observed an influx of minimally mutated IgG+ memory B cells that targeted the receptor binding domain on the S subunit S1 and likely developed from the naive B cell pool. This response was strongly boosted by the second dose and delivers potently neutralizing antibodies against SARS-CoV-2 and several of its variants.
Asunto(s)
Anticuerpos Neutralizantes/inmunología , Anticuerpos Antivirales/inmunología , Linfocitos B/inmunología , Vacuna BNT162/inmunología , SARS-CoV-2/inmunología , Glicoproteína de la Espiga del Coronavirus/inmunología , Anticuerpos Neutralizantes/sangre , Anticuerpos Antivirales/sangre , COVID-19/inmunología , COVID-19/prevención & control , Humanos , Inmunoglobulina A/sangre , Inmunoglobulina A/inmunología , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Células T de Memoria/inmunología , Dominios Proteicos/inmunología , Eficacia de las VacunasRESUMEN
Plasma cells (PC) are found in the CNS of multiple sclerosis (MS) patients, yet their source and role in MS remains unclear. We find that some PC in the CNS of mice with experimental autoimmune encephalomyelitis (EAE) originate in the gut and produce immunoglobulin A (IgA). Moreover, we show that IgA+ PC are dramatically reduced in the gut during EAE, and likewise, a reduction in IgA-bound fecal bacteria is seen in MS patients during disease relapse. Removal of plasmablast (PB) plus PC resulted in exacerbated EAE that was normalized by the introduction of gut-derived IgA+ PC. Furthermore, mice with an over-abundance of IgA+ PB and/or PC were specifically resistant to the effector stage of EAE, and expression of interleukin (IL)-10 by PB plus PC was necessary and sufficient to confer resistance. Our data show that IgA+ PB and/or PC mobilized from the gut play an unexpected role in suppressing neuroinflammation.
Asunto(s)
Inmunoglobulina A/metabolismo , Interleucina-10/metabolismo , Intestinos/inmunología , Animales , Encefalomielitis Autoinmune Experimental/inmunología , Humanos , Inmunoglobulina A/inmunología , Mucosa Intestinal/metabolismo , Ratones , Ratones Endogámicos C57BL , Esclerosis Múltiple/inmunología , Neuroinmunomodulación/inmunología , Células Plasmáticas/metabolismoRESUMEN
Nutritional status potentially influences immune responses; however, how nutritional signals regulate cellular dynamics and functionality remains obscure. Herein, we report that temporary fasting drastically reduces the number of lymphocytes by â¼50% in Peyer's patches (PPs), the inductive site of the gut immune response. Subsequent refeeding seemingly restored the number of lymphocytes, but whose cellular composition was conspicuously altered. A large portion of germinal center and IgA+ B cells were lost via apoptosis during fasting. Meanwhile, naive B cells migrated from PPs to the bone marrow during fasting and then back to PPs during refeeding when stromal cells sensed nutritional signals and upregulated CXCL13 expression to recruit naive B cells. Furthermore, temporal fasting before oral immunization with ovalbumin abolished the induction of antigen-specific IgA, failed to induce oral tolerance, and eventually exacerbated food antigen-induced diarrhea. Thus, nutritional signals are critical in maintaining gut immune homeostasis.
Asunto(s)
Linfocitos B/fisiología , Inmunidad Mucosa , Animales , Antígenos/inmunología , Linfocitos B/inmunología , Linfocitos B/metabolismo , Médula Ósea/inmunología , Médula Ósea/metabolismo , Quimiocina CXCL13/genética , Quimiocina CXCL13/metabolismo , Ayuno , Regulación de la Expresión Génica , Glucólisis , Inmunoglobulina A/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Estado Nutricional , Ovalbúmina/inmunología , Ganglios Linfáticos Agregados/inmunología , Ganglios Linfáticos Agregados/metabolismo , Ganglios Linfáticos Agregados/patología , Receptores CXCR5/genética , Receptores CXCR5/metabolismo , Transducción de Señal , Células del Estroma/citología , Células del Estroma/metabolismo , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
Clinical manifestations of COVID-19 caused by the new coronavirus SARS-CoV-2 are associated with age1,2. Adults develop respiratory symptoms, which can progress to acute respiratory distress syndrome (ARDS) in the most severe form, while children are largely spared from respiratory illness but can develop a life-threatening multisystem inflammatory syndrome (MIS-C)3-5. Here, we show distinct antibody responses in children and adults after SARS-CoV-2 infection. Adult COVID-19 cohorts had anti-spike (S) IgG, IgM and IgA antibodies, as well as anti-nucleocapsid (N) IgG antibody, while children with and without MIS-C had reduced breadth of anti-SARS-CoV-2-specific antibodies, predominantly generating IgG antibodies specific for the S protein but not the N protein. Moreover, children with and without MIS-C had reduced neutralizing activity as compared to both adult COVID-19 cohorts, indicating a reduced protective serological response. These results suggest a distinct infection course and immune response in children independent of whether they develop MIS-C, with implications for developing age-targeted strategies for testing and protecting the population.
Asunto(s)
Anticuerpos Antivirales/inmunología , Formación de Anticuerpos/inmunología , COVID-19/inmunología , Proteínas de la Nucleocápside/inmunología , SARS-CoV-2/inmunología , Glicoproteína de la Espiga del Coronavirus/inmunología , Adolescente , Adulto , Anciano , COVID-19/virología , Niño , Preescolar , Femenino , Humanos , Inmunoglobulina A/inmunología , Inmunoglobulina G/inmunología , Inmunoglobulina M/inmunología , Masculino , Persona de Mediana Edad , SARS-CoV-2/fisiología , Adulto JovenRESUMEN
There is limited understanding of the viral antibody fingerprint following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children. Herein, SARS-CoV-2 proteome-wide immunoprofiling of children with mild/moderate or severe coronavirus disease 2019 (COVID-19) versus multisystem inflammatory syndrome in children versus hospitalized control patients revealed differential cytokine responses, IgM/IgG/IgA epitope diversity, antibody binding and avidity. Apart from spike and nucleocapsid, IgG/IgA recognized epitopes in nonstructural protein (NSP) 2, NSP3, NSP12-NSP14 and open reading frame (ORF) 3a-ORF9. Peptides representing epitopes in NSP12, ORF3a and ORF8 demonstrated SARS-CoV-2 serodiagnosis. Antibody-binding kinetics with 24 SARS-CoV-2 proteins revealed antibody parameters that distinguish children with mild/moderate versus severe COVID-19 or multisystem inflammatory syndrome in children. Antibody avidity to prefusion spike correlated with decreased illness severity and served as a clinical disease indicator. The fusion peptide and heptad repeat 2 region induced SARS-CoV-2-neutralizing antibodies in rabbits. Thus, we identified SARS-CoV-2 antibody signatures in children associated with disease severity and delineate promising serodiagnostic and virus neutralization targets. These findings might guide the design of serodiagnostic assays, prognostic algorithms, therapeutics and vaccines in this important but understudied population.
Asunto(s)
Prueba Serológica para COVID-19/métodos , COVID-19/complicaciones , COVID-19/inmunología , SARS-CoV-2/inmunología , Síndrome de Respuesta Inflamatoria Sistémica/inmunología , Adolescente , Anticuerpos Neutralizantes/metabolismo , Anticuerpos Antivirales/metabolismo , COVID-19/diagnóstico , Niño , Preescolar , Progresión de la Enfermedad , Epítopos/metabolismo , Femenino , Hospitalización , Humanos , Inmunidad Humoral , Inmunoglobulina A/metabolismo , Inmunoglobulina G/metabolismo , Inmunoglobulina M/metabolismo , Masculino , Pronóstico , Proteoma , Índice de Severidad de la Enfermedad , Síndrome de Respuesta Inflamatoria Sistémica/diagnósticoRESUMEN
Mucosal surfaces are colonized by large communities of commensal bacteria and represent the primary site of entry for pathogenic agents. To prevent microbial intrusion, mucosal B cells release large amounts of immunoglobulin (Ig) molecules through multiple follicular and extrafollicular pathways. IgA is the most abundant antibody isotype in mucosal secretions and owes its success in frontline immunity to its ability to undergo transcytosis across epithelial cells. In addition to translocating IgA onto the mucosal surface, epithelial cells educate the mucosal immune system as to the composition of the local microbiota and instruct B cells to initiate IgA responses that generate immune protection while preserving immune homeostasis. Here we review recent advances in our understanding of the cellular interactions and signaling pathways governing IgA production at mucosal surfaces and discuss new findings on the regulation and function of mucosal IgD, the most enigmatic isotype of our mucosal antibody repertoire.
Asunto(s)
Inmunidad Mucosa , Inmunoglobulina A/inmunología , Membrana Mucosa/inmunología , Animales , Linfocitos B/inmunología , Humanos , Inmunoglobulina D/inmunología , Membrana Mucosa/microbiología , Linfocitos T/inmunologíaRESUMEN
Induction of commensal-specific immunity contributes to tissue homeostasis, yet the mechanisms underlying induction of commensal-specific B cells remain poorly understood in part due to a lack of tools to identify these cells. Using phage display, we identified segmented filamentous bacteria (SFB) antigens targeted by serum and intestinal antibodies and generated B cell tetramers to track SFB-specific B cells in gut-associated lymphoid tissues. We revealed a compartmentalized response in SFB-specific B cell activation, with a gradient of immunoglobulin A (IgA), IgG1, and IgG2b isotype production along Peyer's patches contrasted by selective production of IgG2b within mesenteric lymph nodes. V(D)J sequencing and monoclonal antibody generation identified somatic hypermutation driven affinity maturation to SFB antigens under homeostatic conditions. Combining phage display and B cell tetramers will enable investigation of the ontogeny and function of commensal-specific B cell responses in tissue immunity, inflammation, and repair.
Asunto(s)
Linfocitos B , Animales , Linfocitos B/inmunología , Ratones , Ratones Endogámicos C57BL , Ganglios Linfáticos Agregados/inmunología , Activación de Linfocitos/inmunología , Antígenos Bacterianos/inmunología , Hipermutación Somática de Inmunoglobulina , Biblioteca de Péptidos , Ganglios Linfáticos/inmunología , Técnicas de Visualización de Superficie Celular , Simbiosis/inmunología , Inmunoglobulina G/inmunología , Inmunoglobulina A/inmunologíaRESUMEN
In mammals, the gastrointestinal tract harbors an extraordinarily dense and complex community of microorganisms. The gut microbiota provide strong selective pressure to the host to evolve adaptive immune responses required for the maintenance of local and systemic homeostasis. The continuous antigenic presence in the gut imposes a dynamic remodeling of gut-associated lymphoid tissues (GALT) and the selection of multiple layered strategies for immunoglobulin (Ig) A production. The composite and dynamic gut environment also necessitates heterogeneous, versatile, and convertible T cells, capable of inhibiting (Foxp3(+) T cells) or helping (T(FH) cells) local immune responses. In this review, we describe recent advances in our understanding of dynamic pathways that lead to IgA synthesis, in gut follicular structures and in extrafollicular sites, by T cell-dependent and T cell-independent mechanisms. We discuss the finely tuned regulatory mechanisms for IgA production and emphasize the role of mucosal IgA in the selection and maintenance of the appropriate microbial composition that is necessary for immune homeostasis.
Asunto(s)
Inmunidad Adaptativa , Formación de Anticuerpos , Tracto Gastrointestinal/inmunología , Inmunoglobulina A/inmunología , Linfocitos T/inmunología , Animales , Homeostasis , Humanos , Inmunoglobulina A/biosíntesisRESUMEN
Dimeric IgA (dIgA) can move through cells via the IgA/IgM polymeric immunoglobulin receptor (PIGR), which is expressed mainly on mucosal epithelia. Here, we studied the ability of dIgA to target commonly mutated cytoplasmic oncodrivers. Mutation-specific dIgA, but not IgG, neutralized KRASG12D within ovarian carcinoma cells and expelled this oncodriver from tumor cells. dIgA binding changed endosomal trafficking of KRASG12D from accumulation in recycling endosomes to aggregation in the early/late endosomes through which dIgA transcytoses. dIgA targeting of KRASG12D abrogated tumor cell proliferation in cell culture assays. In vivo, KRASG12D-specific dIgA1 limited the growth of KRASG12D-mutated ovarian and lung carcinomas in a manner dependent on CD8+ T cells. dIgA specific for IDH1R132H reduced colon cancer growth, demonstrating effective targeting of a cytoplasmic oncodriver not associated with surface receptors. dIgA targeting of KRASG12D restricted tumor growth more effectively than small-molecule KRASG12D inhibitors, supporting the potential of this approach for the treatment of human cancers.