RESUMEN
Antibody repertoire sequencing provides a molecular fingerprint of current and past pathogens encountered by the immune system. Most repertoire studies in humans require measuring the B cell response in the blood, resulting in a large bias to the IgM isotype. The extent to which the circulating IgM antibody repertoire correlates to lymphoid tissue-resident B cells in the setting of viral infection remains largely uncharacterized. Therefore, we compared the IgM repertoires from both blood and bone marrow (BM) plasma cells (PCs) following acute or chronic lymphocytic choriomeningitis virus (LCMV) infection in mice. Despite previously reported serum alterations between acute and chronic infection, IgM repertoire signatures based on clonal diversity metrics, public clones, network, and phylogenetic analysis were largely unable to distinguish infection cohorts. Our findings, however, revealed mouse-specific repertoire fingerprints between the blood and PC repertoires irrespective of infection status.
Asunto(s)
Coriomeningitis Linfocítica , Animales , Médula Ósea , Inmunoglobulina M , Virus de la Coriomeningitis Linfocítica , Ratones , Ratones Endogámicos C57BL , FilogeniaRESUMEN
Control of established chronic lymphocytic choriomeningitis virus (LCMV) infection requires the production of neutralizing antibodies, but it remains unknown how the ensemble of antibodies evolves during ongoing infection. Here, we analyze the evolution of antibody responses during acute or chronic LCMV infection, combining quantitative functional assays and time-resolved antibody repertoire sequencing. We establish that antibody responses initially converge in both infection types on a functional and repertoire level, but diverge later during chronic infection, showing increased clonal diversity, the appearance of mouse-specific persistent clones, and distinct phylogenetic signatures. Chronic infection is characterized by a longer-lasting germinal center reaction and a continuous differentiation of plasma cells, resulting in the emergence of higher-affinity plasma cells exhibiting increased antibody secretion rates. Taken together, our findings reveal the emergence of a personalized antibody response in chronic infection and support the concept that maintaining B cell diversity throughout chronic LCMV infection correlates with the development of infection-resolving antibodies.
Asunto(s)
Anticuerpos Antivirales/inmunología , Diversidad de Anticuerpos/genética , Evolución Clonal/inmunología , Inmunidad Humoral/genética , Coriomeningitis Linfocítica/inmunología , Coriomeningitis Linfocítica/virología , Virus de la Coriomeningitis Linfocítica/inmunología , Enfermedad Aguda , Animales , Formación de Anticuerpos/genética , Linfocitos B/inmunología , Diferenciación Celular/genética , Diferenciación Celular/inmunología , Línea Celular , Enfermedad Crónica , Evolución Clonal/genética , Centro Germinal/metabolismo , Inmunoglobulina G/inmunología , Virus de la Coriomeningitis Linfocítica/patogenicidad , Ratones , Ratones Endogámicos C57BL , Filogenia , Células Plasmáticas/inmunología , Células Plasmáticas/metabolismo , Hipermutación Somática de InmunoglobulinaRESUMEN
During chronic viral infections, both CD8 and CD4 T cell responses are functionally compromised. Alongside exhaustion of CD8 T cells during chronic viral infections, it has also been documented that the CD4 T cells have an increased propensity to differentiate toward CXCR5+ T follicular helper cell (TFH) lineage. Whether these TFH cells contribute to the immune response to chronic viral infection has remained unclear. Using chronic lymphocytic choriomeningitis virus (LCMV) infection in conjunction with an in vivo system where TFH cells can be conditionally ablated, we have established that these TFH cells do in fact play an important protective function. Specifically, we demonstrate that these TFH cells are essential for the late emergence of neutralizing LCMV-specific antibodies that keep viral titers in check and ultimately allow mice to clear the virus. By supporting the generation of neutralizing antibodies, we show that sustained activity of TFH cells promotes control of the chronic infection in face of exhausted CD8 T cell responses.
Asunto(s)
Coriomeningitis Linfocítica/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Animales , Enfermedad Crónica , Virus de la Coriomeningitis Linfocítica/inmunología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones TransgénicosRESUMEN
MOTIVATION: The evolution of antibody repertoires represents a hallmark feature of adaptive B-cell immunity. Recent advancements in high-throughput sequencing have dramatically increased the resolution to which we can measure the molecular diversity of antibody repertoires, thereby offering for the first time the possibility to capture the antigen-driven evolution of B cells. However, there does not exist a repertoire simulation framework yet that enables the comparison of commonly utilized phylogenetic methods with regard to their accuracy in inferring antibody evolution. RESULTS: Here, we developed AbSim, a time-resolved antibody repertoire simulation framework, which we exploited for testing the accuracy of methods for the phylogenetic reconstruction of B-cell lineages and antibody molecular evolution. AbSim enables the (i) simulation of intermediate stages of antibody sequence evolution and (ii) the modeling of immunologically relevant parameters such as duration of repertoire evolution, and the method and frequency of mutations. First, we validated that our repertoire simulation framework recreates replicates topological similarities observed in experimental sequencing data. Second, we leveraged Absim to show that current methods fail to a certain extent to predict the true phylogenetic tree correctly. Finally, we formulated simulation-validated guidelines for antibody evolution, which in the future will enable the development of accurate phylogenetic methods. AVAILABILITY AND IMPLEMENTATION: https://cran.r-project.org/web/packages/AbSim/index.html. CONTACT: sai.reddy@ethz.ch. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.
Asunto(s)
Linfocitos B/inmunología , Genes de Inmunoglobulinas , Secuenciación de Nucleótidos de Alto Rendimiento , Programas Informáticos , Animales , Anticuerpos/genética , Linaje de la Célula , Simulación por Computador , Evolución Molecular , Femenino , Ratones , FilogeniaRESUMEN
Follicular dendritic cells (FDCs) are stromal cells residing in primary follicles and in germinal centers of secondary and tertiary lymphoid organs (SLOs and TLOs). There, they play a crucial role in B-cell activation and affinity maturation of antibodies. FDCs have the unique capacity to bind and retain native antigen in B-cell follicles for long periods of time. Therefore, FDCs shape the B-cell antigenome (the sum of all B-cell antigens) in SLOs and TLOs. In this review, we discuss recent findings that explain how this stromal cell type can arise in almost any tissue during TLO formation and, furthermore, focus on the mechanisms of antigen capture and retention involved in the generation of long-lasting antigen depots displayed on FDCs.
RESUMEN
Follicular dendritic cells (FDCs) were originally identified by their specific morphology and by their ability to trap immune-complexed antigen in B cell follicles. By virtue of the latter as well as the provision of chemokines, adhesion molecules, and trophic factors, FDCs participate in the shaping of B cell responses. Importantly, FDCs also supply tingible body macrophages (TBMs) with the eat-me-signaling molecule milk fat globule-EGF factor 8 (Mfge8), thereby enabling the disposal of apoptotic B cells. Recent studies have provided fundamental insights into the multiple functions of FDCs in both physiological and pathophysiological contexts and into their origin. Here we review these findings, and discuss current concepts related to FDC histogenesis both in lymphoid organs and in inflammatory lymphoneogenesis.
Asunto(s)
Células Dendríticas Foliculares/citología , Células Dendríticas Foliculares/fisiología , Animales , Humanos , FenotipoRESUMEN
The differentiation of follicular dendritic cells (FDC) is essential to the remarkable microanatomic plasticity of lymphoid follicles. Here we show that FDC arise from ubiquitous perivascular precursors (preFDC) expressing platelet-derived growth factor receptor ß (PDGFRß). PDGFRß-Cre-driven reporter gene recombination resulted in FDC labeling, whereas conditional ablation of PDGFRß(+)-derived cells abolished FDC, indicating that FDC originate from PDGFRß(+) cells. Lymphotoxin-α-overexpressing prion protein (PrP)(+) kidneys developed PrP(+) FDC after transplantation into PrP(-) mice, confirming that preFDC exist outside lymphoid organs. Adipose tissue-derived PDGFRß(+) stromal-vascular cells responded to FDC maturation factors and, when transplanted into lymphotoxin ß receptor (LTßR)(-) kidney capsules, differentiated into Mfge8(+)CD21/35(+)FcγRIIß(+)PrP(+) FDC capable of trapping immune complexes and recruiting B cells. Spleens of lymphocyte-deficient mice contained perivascular PDGFRß(+) FDC precursors whose expansion required both lymphoid tissue inducer (LTi) cells and lymphotoxin. The ubiquity of preFDC and their strategic location at blood vessels may explain the de novo generation of organized lymphoid tissue at sites of lymphocytic inflammation.
Asunto(s)
Vasos Sanguíneos/citología , Células Dendríticas Foliculares/citología , Bazo/citología , Células Madre/citología , Animales , Linfocitos B/inmunología , Células Dendríticas Foliculares/inmunología , Células Dendríticas Foliculares/metabolismo , Centro Germinal/citología , Centro Germinal/inmunología , Centro Germinal/metabolismo , Inflamación/patología , Células Asesinas Naturales/inmunología , Ratones , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/metabolismo , Organismos Libres de Patógenos Específicos , Bazo/metabolismoRESUMEN
Progressive accumulation of PrP(Sc), a hallmark of prion diseases, occurs when conversion of PrP(C) into PrP(Sc) is faster than PrP(Sc) clearance. Engulfment of apoptotic bodies by phagocytes is mediated by Mfge8 (milk fat globule epidermal growth factor 8). In this study, we show that brain Mfge8 is primarily produced by astrocytes. Mfge8 ablation induced accelerated prion disease and reduced clearance of cerebellar apoptotic bodies in vivo, as well as excessive PrP(Sc) accumulation and increased prion titers in prion-infected C57BL/6 × 129Sv mice and organotypic cerebellar slices derived therefrom. These phenotypes correlated with the presence of 129Sv genomic markers in hybrid mice and were not observed in inbred C57BL/6 Mfge8(-/-) mice, suggesting the existence of additional strain-specific genetic modifiers. Because Mfge8 receptors are expressed by microglia and depletion of microglia increases PrP(Sc) accumulation in organotypic cerebellar slices, we conclude that engulfment of apoptotic bodies by microglia may be an important pathway of prion clearance controlled by astrocyte-borne Mfge8.
Asunto(s)
Antígenos de Superficie/biosíntesis , Proteínas de la Leche/biosíntesis , Enfermedades por Prión , Animales , Apoptosis , Astrocitos/metabolismo , Encéfalo/metabolismo , Ratones , Ratones Endogámicos C57BL , Microglía/metabolismo , Proteínas de la Leche/antagonistas & inhibidores , Proteínas PrPSc/metabolismo , Enfermedades por Prión/genética , Enfermedades por Prión/patología , Enfermedades por Prión/fisiopatología , Especificidad de la EspecieRESUMEN
The susceptibility of humans and animals to prion infections is determined by the virulence of the infectious agent, by genetic modifiers, and by hitherto unknown host and environmental risk factors. While little is known about the latter two, the activation state of the immune system was surmised to influence prion susceptibility. Here we administered prions to mice that were repeatedly immunized by two initial injections of CpG oligodeoxynucleotides followed by repeated injections of bovine serum albumin/alum. Immunization greatly reduced the required dosage of peripherally administered prion inoculum necessary to induce scrapie in 50% of mice. No difference in susceptibility was observed following intracerebral prion challenge. Due to its profound impact onto scrapie susceptibility, the host immune status may determine disease penetrance after low-dose prion exposure, including those that may give rise to iatrogenic and variant Creutzfeldt-Jakob disease.
Asunto(s)
Inmunización/métodos , Priones/metabolismo , Scrapie/prevención & control , Animales , Bovinos , Islas de CpG , Síndrome de Creutzfeldt-Jakob/prevención & control , Susceptibilidad a Enfermedades , Femenino , Hibridación in Situ , Ratones , Ratones Endogámicos C57BL , Oligonucleótidos/química , Factores de Riesgo , Albúmina Sérica Bovina/químicaRESUMEN
The secreted phosphatidylserine-binding protein milk fat globule epidermal growth factor 8 (Mfge8) mediates engulfment of apoptotic germinal center B cells by tingible-body macrophages (TBMphis). Impairment of this process can contribute to autoimmunity. We show that Mfge8 is identical to the mouse follicular dendritic cell (FDC) marker FDC-M1. In bone-marrow chimeras between wild-type and Mfge8(-/-) mice, all splenic Mfge8 was derived from FDCs rather than TBMphis. However, Mfge8(-/-) TBMphis acquired and displayed Mfge8 only when embedded in Mfge8(+/+) stroma, or when situated in lymph nodes draining exogenous recombinant Mfge8. These findings indicate a licensing role for FDCs in TBMphi-mediated removal of excess B cells. Lymphotoxin-deficient mice lacked FDCs and splenic Mfge8, and suffer from autoimmunity similar to Mfge8(-/-) mice. Hence, FDCs facilitate TBMphi-mediated corpse removal, and their malfunction may be involved in autoimmunity.