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Project description:Co-ordinated humoral and cell-mediated immune responses drive class-switched antibody production and improved patient survival in endometrial cancer
| PRJNA748350 | ENA
Project description:BackgroundFollicular structures resembling germinal centres (GCs) that are characterized by follicular dendritic cell (FDC) networks have long been recognized in chronically inflamed tissues in autoimmune diseases, including the synovium of rheumatoid arthritis (RA). However, it is debated whether these ectopic structures promote autoimmunity and chronic inflammation driving the production of pathogenic autoantibodies. Anti-citrullinated protein/peptide antibodies (ACPA) are highly specific markers of RA, predict a poor prognosis, and have been suggested to be pathogenic. Therefore, the main study objectives were to determine whether ectopic lymphoid structures in RA synovium: (i) express activation-induced cytidine deaminase (AID), the enzyme required for somatic hypermutation and class-switch recombination (CSR) of Ig genes; (ii) support ongoing CSR and ACPA production; and (iii) remain functional in a RA/severe combined immunodeficiency (SCID) chimera model devoid of new immune cell influx into the synovium.Methods and findingsUsing immunohistochemistry (IHC) and quantitative Taqman real-time PCR (QT-PCR) in synovial tissue from 55 patients with RA, we demonstrated that FDC+ structures invariably expressed AID with a distribution resembling secondary lymphoid organs. Further, AID+/CD21+ follicular structures were surrounded by ACPA+/CD138+ plasma cells, as demonstrated by immune reactivity to citrullinated fibrinogen. Moreover, we identified a novel subset of synovial AID+/CD20+ B cells outside GCs resembling interfollicular large B cells. In order to gain direct functional evidence that AID+ structures support CSR and in situ manufacturing of class-switched ACPA, 34 SCID mice were transplanted with RA synovium and humanely killed at 4 wk for harvesting of transplants and sera. Persistent expression of AID and Igamma-Cmu circular transcripts (identifying ongoing IgM-IgG class-switching) was observed in synovial grafts expressing FDCs/CD21L. Furthermore, synovial mRNA levels of AID were closely associated with circulating human IgG ACPA in mouse sera. Finally, the survival and proliferation of functional B cell niches was associated with persistent overexpression of genes regulating ectopic lymphoneogenesis.ConclusionsOur demonstration that FDC+ follicular units invariably express AID and are surrounded by ACPA-producing plasma cells provides strong evidence that ectopic lymphoid structures in the RA synovium are functional and support autoantibody production. This concept is further confirmed by evidence of sustained AID expression, B cell proliferation, ongoing CSR, and production of human IgG ACPA from GC+ synovial tissue transplanted into SCID mice, independently of new B cell influx from the systemic circulation. These data identify AID as a potential therapeutic target in RA and suggest that survival of functional synovial B cell niches may profoundly influence chronic inflammation, autoimmunity, and response to B cell-depleting therapies.
| S-EPMC2621263 | biostudies-literature
Project description:We report that a large percentage of thymic B cells undergo class switching intrathymically. Thymic B cell class switching requires cognate T-B interaction. To determine whether B cell specificity was also important for thymic B cell class-switching, we sorted class-switched thymic B cells (CD19+B220+IgM-IgD-), unswitched B cells (CD19+B220+IgM+IgD+) and bulk splenic B cells in 3H9 heavy chain-fixed mice and performed high throughput sequencing analysis of the light chain of these populations. Results of this analysis indicated that class-switched thymic B cells have a distinct repertoire compared with unswitched thymic B cells and splenic B cells. Further reactivity tests indicated that a large part of BCRs enriched in class-switched thymic B cells are autoreactive. These data suggest that autoreactive B cells are selected into class-switched population and expanded in the thymus.
2016-08-10 | GSE85366 | GEO
Project description:We report that a large percentage of thymic B cells undergo class switching intrathymically. Thymic B cell class switching requires cognate T-B interaction. To determine whether B cell specificity was also important for thymic B cell class-switching, we sorted class-switched thymic B cells (CD19+B220+IgM-IgD-), unswitched B cells (CD19+B220+IgM+IgD+) and bulk splenic B cells in 3H9 heavy chain-fixed mice and performed high throughput sequencing analysis of the light chain of these populations. Results of this analysis indicated that class-switched thymic B cells have a distinct repertoire compared with unswitched thymic B cells and splenic B cells. Further reactivity tests indicated that a large part of BCRs enriched in class-switched thymic B cells are autoreactive. These data suggest that autoreactive B cells are selected into class-switched population and expanded in the thymus. Light chain repertoire profiles of class-switched thymic B cells, unswithced thymic B cells and splenic B cells from 3H9 mice were generated by deep sequencing.
2016-08-10 | E-GEOD-85366 | biostudies-arrayexpress
Project description:Secondary antibody responses are marked by faster kinetics, improved antibody affinity and a switch from IgM to other immunoglobulin isotypes, most notably IgG, compared with primary responses. These changes protect from reinfection and represent the principle of most vaccination strategies. Yet, the molecular mechanisms that underlie B-cell memory responses are unclear. Here we show, by inactivating the immunoglobulin tail tyrosine (ITT) signalling motif of membrane-bound IgG1 in the mouse, that the ITT facilitates maintenance and reactivation of IgG-switched memory B cells in vivo. The ITT motif equips IgG-switched cells with enhanced BCR signalling capacity, which supports their competitiveness in secondary immune reactions and drives the formation of IgG-secreting plasma cells even in the absence of T-cell help. Our results demonstrate that ITT signalling promotes the vigorous production of IgG antibodies and thus provide a molecular basis for humoral immunological memory.
| S-EPMC4633962 | biostudies-literature
Project description:The increased susceptibility to infections of neonates is caused by an immaturity of the immune system as a result of both qualitative and quantitative differences between neonatal and adult immune cells. With respect to B cells, neonatal antibody responses are known to be decreased. Accountable for this is an altered composition of the neonatal B cell compartment towards more immature B cells. However, it remains unclear whether the functionality of individual neonatal B cell subsets is altered as well. In the current study we therefore compared phenotypical and functional characteristics of corresponding neonatal and adult B cell subpopulations. No phenotypic differences could be identified with the exception of higher IgM expression in neonatal B cells. Functional analysis revealed differences in proliferation, survival, and B cell receptor signaling. Most importantly, neonatal B cells showed severely impaired class-switch recombination (CSR) to IgG and IgA. This was associated with increased expression of miR-181b in neonatal B cells. Deficiency of miR-181b resulted in increased CSR. With this, our results highlight intrinsic differences that contribute to weaker B cell antibody responses in newborns.
| S-EPMC5794184 | biostudies-literature
Project description:Anti-B cell activating factor belonging to TNF-family (BAFF) antibody therapy is indicated for the treatment of patients with active systemic lupus erythematosus (SLE). We hypothesized that the BAFF receptor, transmembrane activator and calcium-modulator and cyclophilin interactor (TACI) may be responsible for the generation of antibody secreting plasma cells in SLE. To test this hypothesis, we generated TACI deficient MRL-Fas/Lpr (LPR-TACI-/-) mouse. TACI deficiency resulted in improved survival of MRL-Fas/Lpr mice and delayed production of anti-dsDNA and anti-SAM/RNP antibodies. There was also a delay in the onset of proteinuria and the accumulation of IgG and inflammatory macrophages (M?s) in the glomeruli of young LPR-TACI-/- mice compared to wild-type mice. Underscoring the role of TACI in influencing M? phenotype, the transfer of M?s from 12-week-old LPR-TACI-/- mice to age-matched sick wild-type animals led to a decrease in proteinuria and improvement in kidney pathology. The fact that, in LPR-TACI-/- mouse a more pronounced delay was in IgM and IgG3 autoreactive antibody isotypes and the kinetics of follicular helper T (Tfh) cell-development was comparable between the littermates suggest a role for TACI in T cell-independent autoantibody production in MRL-Fas/Lpr mouse prior to the onset of T cell-dependent antibody production.
| S-EPMC5778001 | biostudies-literature
Project description:We purified 4 Ig class switched memory B cell populations from human adults to compare their gene expression profiles with each other and with those of human naive and IgM memory B cells generated in a previous experiment (E-MEXP-3767).
2015-07-07 | E-MTAB-3637 | biostudies-arrayexpress
Project description:microRNA-155 (miR-155) is expressed by cells of the immune system after activation and has been shown to be required for antibody production after vaccination with attenuated Salmonella. Here we show the intrinsic requirement for miR-155 in B cell responses to thymus-dependent and -independent antigens. B cells lacking miR-155 generated reduced extrafollicular and germinal center responses and failed to produce high-affinity IgG1 antibodies. Gene-expression profiling of activated B cells indicated that miR-155 regulates an array of genes with diverse function, many of which are predicted targets of miR-155. The transcription factor Pu.1 is validated as a direct target of miR155-mediated inhibition. When Pu.1 is overexpressed in wild-type B cells, fewer IgG1 cells are produced, indicating that loss of Pu.1 regulation is a contributing factor to the miR-155-deficient phenotype. Our results implicate post-transcriptional regulation of gene expression for establishing the terminal differentiation program of B cells.
| S-EPMC4135426 | biostudies-literature
Project description:Effective vaccines induce high-affinity memory B cells and durable antibody responses through accelerated mechanisms of natural selection. Secondary changes in antibody repertoires after vaccine boosts suggest progressive rediversification of B cell receptors (BCRs), but the underlying mechanisms remain unresolved. Here, the integrated specificity and function of individual memory B cell progeny revealed ongoing evolution of polyclonal antibody specificities through germinal center (GC)-specific transcriptional activity. At the clonal and subclonal levels, single-cell expression of the genes encoding the costimulatory molecule CD83 and the DNA polymerase Pol? segregated the secondary GC transcriptional program into four stages that regulated divergent mechanisms of memory BCR evolution. Our studies demonstrate that vaccine boosts reactivate a cyclic program of GC function in class-switched memory B cells to remodel existing antibody specificities and enhance durable immunological protection.
| S-EPMC4333102 | biostudies-literature