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MTORC1 and B cell survival signal regulate formation of memory precursors in the germinal center [2]

ABSTRACT: A still unanswered question is what drives the small fraction of activated germinal center (GC) B cells that survive to become long-lived quiescent memory B cells. We found here that a small population of light zone GC cells (CD38intBcl6hi/intEfnb1+) with lower mTORC1 activity favored the memory B cell fate. Constitutively high mTORC1 activity led to defects in formation of the CD38intBcl6hi/intEfnb1+ cells; conversely, decreasing mTORC1 activity resulted in relative enrichment of this memory-prone GC population over the recycling-prone one. Furthermore, the CD38intBcl6hi/intEfnb1+ cells had higher levels of Bcl2 and surface BCR, which in turn, contributed to their survival. Given the positive correlation between the strength of T cell help and mTORC1 activity, our data suggest a model in which weak help from T cells together with provision of an increased survival signal are key for GC B cells to assume a memory B cell fate.

ORGANISM(S): Mus musculus

PROVIDER: GSE147095 | GEO | 2020/09/13

REPOSITORIES: GEO

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mTORC1 and B cell survival signal regulate formation of memory precursors in the germinal center [1]

Project description:A still unanswered question is what drives the small fraction of activated germinal center (GC) B cells that survive to become long-lived quiescent memory B cells. We found here that a small population of light zone GC cells (CD38intBcl6hi/intEfnb1+) with lower mTORC1 activity favored the memory B cell fate. Constitutively high mTORC1 activity led to defects in formation of the CD38intBcl6hi/intEfnb1+ cells; conversely, decreasing mTORC1 activity resulted in relative enrichment of this memory-prone GC population over the recycling-prone one. Furthermore, the CD38intBcl6hi/intEfnb1+ cells had higher levels of Bcl2 and surface BCR, which in turn, contributed to their survival. Given the positive correlation between the strength of T cell help and mTORC1 activity, our data suggest a model in which weak help from T cells together with provision of an increased survival signal are key for GC B cells to assume a memory B cell fate.

2020-09-13 | GSE146922 | GEO

Comparison of NP specific high and low affinity IgG1 Light zone GC B cells

Project description:Despite the importance of memory B cells for protection from recurrent infection, how these cells are selected during germinal center (GC) reactions remains unclear. We show here that light zone (LZ) GC B cells with lower affinity BCRs express a less CD40 signature and relatively high levels of Bach2, being prone to enter the memory B cell pool. We also find that Bach2 contributes to memory B cell generation in a Blimp-1 independent manner and that its higher expression confers on LZ GC cells a more advantage for entering the memory B cell compartment. Thus, our data support an instructive model in which weak T cell help keeps Bach2 expression relatively high, thereby being predisposed to enter the memory pool.

2016-05-09 | GSE73729 | GEO

Comparison of Bach2-tdRFP high expression and low expression NP-specific IgG1 light zone GC B cells

Project description:Despite the importance of memory B cells for protection from recurrent infection, how these cells are selected during germinal center (GC) reactions remains unclear. We show here that light zone (LZ) GC B cells with lower affinity BCRs express a less CD40 signature and relatively high levels of Bach2, being prone to enter the memory B cell pool. We also find that Bach2 contributes to memory B cell generation in a Blimp-1-independent manner and that its higher expression confers on LZ GC cells a more advantage for entering the memory B cell compartment. Thus, our data support an instructive model in which weak T cell help keep Bach2 expression relatively high, thereby being predisposed to enter the memory pool.

2016-05-09 | GSE77319 | GEO

Spatiotemporal dynamics of Bach2 orchestrates B cell responses and fate decision

Project description:The molecular circuits that direct early T-dependent B cell responses and alternative cell-fate decisions remain poorly understood. Here, we show that either B cell receptor (BCR) or CD40 signals promoted mTORC1-dependent translation of the transcription factor Bach2. Transient up-regulation of Bach2 protein restrained activated B cell expansion and differentiation into plasma cell while promoting the germinal center (GC) and memory B cell fates at the pre-GC stage. However, enforced Bach2 expression facilitated memory B cell generation versus other cell fates. Mechanistically, Bach2 limited access of AP-1 factors and formed a reciprocal repression loop with IRF4. BCR and CD40 signals also down-regulated Bach2 transcript in antigen-activated B cells, and diversified its abundance in various effector populations, predisposing Bach2 protein expression and subsequent cell-fate choices during memory recall and GC reaction. Thus signaling-induced differential dynamics of Bach2 protein and mRNA in activated B cell control their cell-fate outcomes and imprint the fate of their descendant effector cells.

2021-07-18 | GSE180277 | GEO

Spatiotemporal dynamics of Bach2 orchestrates B cell responses and fate decision II

2022-06-08 | GSE180460 | GEO

Limited access to antigen drives the generation of early B cell memory while restraining the plasmablast response

Project description:The cell fate decisions between plasmablasts (PBs), germinal center B cells (GCBCs) and non-GC-derived memory B cells (MBCs) during early B cell activation determine the outcome of the immune responses to pathogens and vaccines. In this study, we dissected these poorly characterized lineage choices by single-cell RNA-sequencing. Early after immunization, a homogenous population of activated precursors (APs) gave rise to a transient wave of PBs, followed a day later by the emergence of the first GCBCs, with the transcriptomes of both rapidly diverging from that of APs. The majority of APs started to withdraw from the cell cycle very early on and gave rise to GC-independent MBCs, a developmental transition that involved limited transcriptional changes. These events were controlled by antigen availability, and provision of antigen excess interfered with cell cycle exit and induced a new wave of PBs. Fate mapping experiments revealed a prominent contribution of GC-independent memory to the overall MBC pool. Quiescent cells with an MBC phenotype also dominated the early response to immunization in primates, indicating evolutionary conservation. Thus, excess APs, kept in reserve as early MBCs, can be rapidly re-recruited if failure to contain a threat is manifested by increased antigen availability, thus providing a feedback mechanism for rapid readjustment of the immune response.

2021-08-19 | GSE175427 | GEO

Development of plasma cell-prone germinal center B cells

Project description:Higher- or lower-affinity GC B cells are directed to plasma cell or recycling GC cell fates; however, how commitment to the plasma cell fate takes place is unclear. By using the level of Bcl6 as a marker, we found that a population of light zone (LZ) GC cells, Bcl6loCD69hi with IRF4 and higher-affinity BCRs or Bcl6hiCD69hi with lower- affinity BCRs, favored the plasma cell or recycling GC cell fate, respectively. Mechanistically, CD40 acted as a dose-dependent regulator for Bcl6loCD69hi cell formation. Furthermore, we found that ICAM1 and SLAM levels on Bcl6loCD69hi cells were higher than on Bcl6hiCD69hi cells, thereby affording more stable TFH-GC B cell contacts, while attenuating this contact down-regulated IRF4. These data support the model that commitment to the plasma cell begins in the GC, and suggest that stability and possibly duration of TFH-GC B cell contacts are key for formation of plasma cell-prone precursor GC cells.

2018-03-29 | GSE109732 | GEO

Expression data from IgE+ and IgG1+ B lymphocytes in mice infected with Nippostrongylus brasiliensis

Project description:The mechanisms involved in the maintenance of memory IgE responses are poorly understood, and the role played by germinal center (GC) IgE cells in these memory responses is particularly unclear. IgE B-cell differentiation is characterized by a transient GC phase, a bias towards the plasma cell (PC) fate, and dependence on sequential switching for the production of high-affinity IgE. We show here that IgE GC B cells are unfit to undergo the conventional GC differentiation program due to impaired B-cell receptor function and increased apoptosis. IgE GC cells fail to populate the GC light zone and are unable to contribute to the memory and long-lived PC compartments. Furthermore, we demonstrate that direct and sequential switching are linked to distinct B-cell differentiation fates: direct switching generates IgE GC cells, whereas sequential switching gives rise to IgE plasma cells. We propose a comprehensive model for the generation and memory of IgE responses. The purpose of this analysis was to: 1) identify expression differences between IgE and IgG1 B lymphocytes, 2) identify GC Dark Zone (DZ) and Light Zone (LZ) signatures of IgG1 GC cells. For that purpose, we compared in one experiment the gene expression patterns of IgE germinal center (GC) cells, IgG1 GC cells, IgE plasma cells (PC), IgG1 PC and naïve cells. In a second experiment, we compared the expression of IgG1 DZ GC cells with that of IgG1 LZ GC cells. Triplicates obtained from independent sorting experiments were used for all samples except two (IgG1 PC=2 samples; IgE PC=4 samples). Each sample was obtained from a pool of three individual mice. The mice used in the experiment were CeGFP BALB/c mice infected with the parasite N. brasiliensis. CeGFP mice carry an IRES-GFP KI cassette in the 3'UTR of membrane IgE. In these mice, GFP expression marks IgE cells, and a population of IgG1 cells with a rearrangement to Cepsilon in the non-productive (VDJ negative) IgH chromosome.

2013-10-31 | E-GEOD-49033 | biostudies-arrayexpress

The transcription factor Foxo1 controls germinal center B cell proliferation in response to T cell help

Project description:Germinal center (GC) B cells cycle between two states, the light zone (LZ) and the dark zone (DZ), and in the latter they proliferate and hypermutate their immunoglobulin genes. How this functional transition takes place is still controversial. In this study, we demonstrate that ablation of Foxo1 after GC development led to the loss of the DZ GC B cells and disruption of the GC architecture. Mechanistically, even upon provision of adequate T cell help, Foxo1-deficient GC B cells showed less proliferative expansion than controls. Moreover, we found that the transcription factor BATF was transiently induced in LZ GC B cells in a Foxo1-dependent manner and that deletion of BATF similarly led to GC disruption. Thus, our results are consistent with a model where the switch from the LZ to the DZ is triggered after receipt of T cell help, and suggest that Foxo1-mediated BATF up-regulation is at least partly involved in this switch.

2017-03-21 | GSE93554 | GEO

CD73+ memory CD4 T cells are a long-lived population with elevated effector function and prone to differentiate into TRM-like cells [RNA-seq]

Project description:The understanding of heterogeneity of human memory T cells will help to know the function, development and maintenance of memory population, then to improve the recall response or effective immunotherapy. Ecto-5’-nucleotidase CD73 expression in four subsets of memory T cells decreases with aging. The resistance to apoptosis and high expression of IL7R entitle CD73+ memory T cells to be long-lived population. We found antigen-specific memory T cells have overwhelming CD73 expression. The transcriptional and chromatin accessibility profiles indicate the elevated effector functions in CD73+ memory CD4 T cells comparing to CD73- counterparts. Homer analysis and Transcriptional factor (TF)-regulatory element-target gene triplet network clearly show the crucial role of RUNT and NR family TFs in CD73+ cells. Furthermore, CD73+ memory CD4 T cells were prone to differentiate into TRM-like cells under in-vitro sequential TCR and TGF/IL-15 signaling. The decreased percentage of CD73+ memory T cells with age leads to the less replenishment of TRM cells from peripheral blood.

2021-08-28 | GSE157163 | GEO

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