Transcription factor T-bet in B cells controls germinal centre polarization and antibody affinity maturation in response to malaria
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE120729 | GEO | 2019/11/11
REPOSITORIES: GEO
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Project description:Despite the key role that antibodies play in protection against malaria, the cellular processes modulating the acquisition of immunity are not fully understood. Using an infection model of severe malaria, we found that GC B cells strongly upregulate the transcription factor T-bet in response to infection. Expression of T-bet in B cells was required for IgG2c switching but reduced the magnitude of GC B cell responses. RNA-sequencing and flow cytometry analysis revealed that T-bet supports a transcriptional program resulting in a substantial enrichment of the GC dark zone (DZ), thereby significantly influencing DZ/light zone (LZ) polarization. Mice deficient in T-bet in their B cells displayed significantly reduced affinity mutation frequencies in their IghV genes and lower antibody avidity than controls, indicating that T-bet modulates affinity maturation. These results demonstrate that T-bet promotes appropriate GC dynamics, thereby leading to the differentiation of B cells with increased affinity for antigen.
2019-11-11 | GSE120727 | GEO
Project description:Despite the key role that antibodies play in protection against malaria, the cellular processes modulating the acquisition of immunity are not fully understood. Using an infection model of severe malaria, we found that GC B cells strongly upregulate the transcription factor T-bet in response to infection. Expression of T-bet in B cells was required for IgG2c switching but reduced the magnitude of GC B cell responses. RNA-sequencing and flow cytometry analysis revealed that T-bet supports a transcriptional program resulting in a substantial enrichment of the GC dark zone (DZ), thereby significantly influencing DZ/light zone (LZ) polarization. Mice deficient in T-bet in their B cells displayed significantly reduced affinity mutation frequencies in their IghV genes and lower antibody avidity than controls, indicating that T-bet modulates affinity maturation. These results demonstrate that T-bet promotes appropriate GC dynamics, thereby leading to the differentiation of B cells with increased affinity for antigen.
2019-11-11 | GSE120728 | GEO
Project description:Transcription factor T-bet in B cells controls germinal centre polarization and antibody affinity maturation in response to malaria
| PRJNA494310 | ENA
Project description:Transcription factor T-bet in B cells controls germinal centre polarization and antibody affinity maturation in response to malaria (RNA-seq)
| PRJNA494311 | ENA
Project description:Transcription factor T-bet in B cells controls germinal centre polarization and antibody affinity maturation in response to malaria (ATAC-seq)
| PRJNA494312 | ENA
Project description:Antibodies somatically mutate to attain high affinity in germinal centers (GCs). There, competition between B cell clones and among somatic mutants of each clone drives an increase in average affinity across the population. The extent to which higher-affinity cells eliminating competitors restricts clonal diversity is unknown. By combining multiphoton microscopy and sequencing, we show that tens to hundreds of distinct B cell clones seed each GC and that GCs lose clonal diversity at widely disparate rates. Furthermore, efficient affinity maturation can occur in the absence of homogenizing selection, ensuring that many clones can mature in parallel within the same GC. Our findings have implications for development of vaccines in which antibodies with nonimmunodominant specificities must be elicited, as is the case for HIV-1 and influenza.
| S-EPMC4938154 | biostudies-literature
Project description:Two immunoglobulin (Ig) diversification mechanisms collaborate to provide protective humoral immunity. Combinatorial assembly of IgH and IgL V region exons from gene segments generates preimmune Ig repertoires, expressed as B cell receptors (BCRs). Secondary diversification occurs when Ig V regions undergo somatic hypermutation (SHM) and affinity-based selection toward antigen in activated germinal center (GC) B cells. Secondary diversification is thought to only ripen the antigen-binding affinity of Igs that already exist (i.e., cognate Igs) because of chance generation during preimmune Ig diversification. However, whether stochastic activation of noncognate B cells can generate new affinity to antigen in GCs is unclear. Using a mouse model whose knock-in BCR does not functionally engage with immunizing antigen, we found that chronic immunization induced antigen-specific serological responses with diverse SHM-mediated antibody affinity maturation pathways and divergent epitope targeting. Thus, intrinsic GC B cell flexibility allows for somatic, noncognate B cell evolution, permitting de novo antigen recognition and subsequent antibody affinity maturation without initial preimmune BCR engagement.
| S-EPMC5748855 | biostudies-literature
Project description:ObjectiveNLRP3 inflammasome regulates T cell responses. This study examined the roles of NLRP3 inflammasome activation in the regulation of T follicular helper (Tfh) cells during humoral response to T dependent antigens and in systemic lupus erythematosus (SLE).MethodsNLRP3 inflammasome activation of Tfh cells was studied in B6, MRL/lpr and NZM2328 mice and in SLE patients and healthy controls using a fluorescence-labelled caspase-1 inhibitor probe. MCC950, a selective inhibitor of NLRP3, was used to investigate the relation between NLRP3 inflammasome activation and germinal centre (GC) reaction, Ab responses to immunisation, and autoantibody production.ResultsNLRP3 inflammasome activation in Tfh cells after immunisation was identified in B6 mice. MCC950 inhibited humoral responses to sheep red blood cell and NP-CGG with reduction of the GC reaction. B6 mice with lymphoid cell-specific deletion of NLRP3 or Casp1 mounted suboptimal humoral responses with impaired GC formation and defective affinity maturation. In MRL/lpr and NZM2328 mice, inhibition of NLRP3 activation suppressed NLRP3 activated Tfh cell expansion as well as attenuated lupus-like phenotypes. Tfh cells with activated NLRP3 inflammasome exhibited increased expression of molecules for Tfh cell function and differentiation, and had greater ability to activate B cells. In SLE patients, disease activity was positively correlated with an increase in the activated NLRP3+ Tfh population and this population was markedly reduced in response to therapy.ConclusionsThe activation of NLRP3 inflammasome in Tfh cells is an integral part of responses to immunisation. The activated NLRP3+ Tfh population is essential for optimal humoral responses, GC formation and autoimmunity.
| S-EPMC9262832 | biostudies-literature
Project description:Nearly all chronic human infections are associated with alterations in the memory B cell (MBC) compartment, including a large expansion of CD19hiT-bethi MBC in the peripheral blood of HIV-infected individuals with chronic viremia. Despite their prevalence, it is unclear how these B cells arise and whether they contribute to the inefficiency of antibody-mediated immunity in chronic infectious diseases. We addressed these questions by characterizing T-bet-expressing B cells in lymph nodes (LN) and identifying a strong T-bet signature among HIV-specific MBC associated with poor immunologic outcome. Confocal microscopy and quantitative imaging revealed that T-bethi B cells in LN of HIV-infected chronically viremic individuals distinctly accumulated outside germinal centers (GC), which are critical for optimal antibody responses. In single-cell analyses, LN T-bethi B cells of HIV-infected individuals were almost exclusively found among CD19hi MBC and expressed reduced GC-homing receptors. Furthermore, HIV-specific B cells of infected individuals were enriched among LN CD19hiT-bethi MBC and displayed a distinct transcriptome, with features similar to CD19hiT-bethi MBC in blood and LN GC B cells (GCBC). LN CD19hiT-bethi MBC were also related to GCBC by B cell receptor (BCR)-based phylogenetic linkage but had lower BCR mutation frequencies and reduced HIV-neutralizing capacity, consistent with diminished participation in GC-mediated affinity selection. Thus, in the setting of chronic immune activation associated with HIV viremia, failure of HIV-specific B cells to enter or remain in GC may help explain the rarity of high-affinity protective antibodies.
| S-EPMC7479651 | biostudies-literature
Project description:The antigen-binding variable regions of the B cell receptor (BCR) and of antibodies are encoded by exons that are assembled in developing B cells by V(D)J recombination1. The BCR repertoires of primary B cells are vast owing to mechanisms that create diversity at the junctions of V(D)J gene segments that contribute to complementarity-determining region 3 (CDR3), the region that binds antigen1. Primary B cells undergo antigen-driven BCR affinity maturation through somatic hypermutation and cellular selection in germinal centres (GCs)2,3. Although most GCs are transient3, those in intestinal Peyer's patches (PPs)-which depend on the gut microbiota-are chronic4, and little is known about their BCR repertoires or patterns of somatic hypermutation. Here, using a high-throughput assay that analyses both V(D)J segment usage and somatic hypermutation profiles, we elucidate physiological BCR repertoires in mouse PP GCs. PP GCs from different mice expand public BCR clonotypes (clonotypes that are shared between many mice) that often have canonical CDR3s in the immunoglobulin heavy chain that, owing to junctional biases during V(D)J recombination, appear much more frequently than predicted in naive B cell repertoires. Some public clonotypes are dependent on the gut microbiota and encode antibodies that are reactive to bacterial glycans, whereas others are independent of gut bacteria. Transfer of faeces from specific-pathogen-free mice to germ-free mice restored germ-dependent clonotypes, directly implicating BCR selection. We identified somatic hypermutations that were recurrently selected in such public clonotypes, indicating that affinity maturation occurs in mouse PP GCs under homeostatic conditions. Thus, persistent gut antigens select recurrent BCR clonotypes to seed chronic PP GC responses.
| S-EPMC7478071 | biostudies-literature