scholarly journals Low-level Hypermutation in T Cell–independent Germinal Centers Compared with High Mutation Rates Associated with T Cell–dependent Germinal Centers

2002 ◽  
Vol 195 (3) ◽  
pp. 383-389 ◽  
Author(s):  
Kai-Michael Toellner ◽  
William E. Jenkinson ◽  
Dale R. Taylor ◽  
Mahmood Khan ◽  
Daniel M.-Y. Sze ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Plasma Cells ◽  
Cell Receptor ◽  
Similar Rate ◽  
Germinal Centers ◽  
Stage Of Development ◽  
V Region ◽  
T Cell Help

Exceptionally germinal center formation can be induced without T cell help by polysaccharide-based antigens, but these germinal centers involute by massive B cell apoptosis at the time centrocyte selection starts. This study investigates whether B cells in germinal centers induced by the T cell–independent antigen (4-hydroxy-3-nitrophenyl)acetyl (NP) conjugated to Ficoll undergo hypermutation in their immunoglobulin V region genes. Positive controls are provided by comparing germinal centers at the same stage of development in carrier-primed mice immunized with a T cell–dependent antigen: NP protein conjugate. False positive results from background germinal centers and false negatives from non-B cells in germinal centers were avoided by transferring B cells with a transgenic B cell receptor into congenic controls not carrying the transgene. By 4 d after immunization, hypermutation was well advanced in the T cell–dependent germinal centers. By contrast, the mutation rate for T cell–independent germinal centers was low, but significantly higher than in NP-specific B cells from nonimmunized transgenic mice. Interestingly, a similar rate of mutation was seen in extrafollicular plasma cells at this stage. It is concluded that efficient activation of hypermutation depends on interaction with T cells, but some hypermutation may be induced without such signals, even outside germinal centers.

scholarly journals Regulation of B cell fate by chronic activity of the IgE B cell receptor

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Zhiyong Yang ◽  
Marcus J Robinson ◽  
Xiangjun Chen ◽  
Geoffrey A Smith ◽  
Jack Taunton ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Fate ◽  
Plasma Cells ◽  
Cell Receptor ◽  
Culture Conditions ◽  
B Cell Receptor ◽  
Cell Cycles ◽  
T Cell Help

IgE can trigger potent allergic responses, yet the mechanisms regulating IgE production are poorly understood. Here we reveal that IgE+ B cells are constrained by chronic activity of the IgE B cell receptor (BCR). In the absence of cognate antigen, the IgE BCR promoted terminal differentiation of B cells into plasma cells (PCs) under cell culture conditions mimicking T cell help. This antigen-independent PC differentiation involved multiple IgE domains and Syk, CD19, BLNK, Btk, and IRF4. Disruption of BCR signaling in mice led to consistently exaggerated IgE+ germinal center (GC) B cell but variably increased PC responses. We were unable to confirm reports that the IgE BCR directly promoted intrinsic apoptosis. Instead, IgE+ GC B cells exhibited poor antigen presentation and prolonged cell cycles, suggesting reduced competition for T cell help. We propose that chronic BCR activity and access to T cell help play critical roles in regulating IgE responses.

scholarly journals Long-Lasting T Cell-Independent IgG Responses Require MyD88-Mediated Pathways and Are Maintained by High Levels of Virus Persistence

mBio ◽  
2013 ◽  
Vol 4 (6) ◽  
Author(s):  
Forum M. Raval ◽  
Rabinarayan Mishra ◽  
Robert L. Garcea ◽  
Raymond M. Welsh ◽  
Eva Szomolanyi-Tsuda
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Plasma Cells ◽  
Cell Receptor ◽  
Cell Responses ◽  
Serum Igg ◽  
B Cell Memory ◽  
T Cell Help ◽  
Serum Igg Levels

ABSTRACTMany viruses induce acute T cell-independent (TI) B cell responses due to their repetitive epitopes and the induction of innate cytokines. Nevertheless, T cell help is thought necessary for the development of long-lasting antiviral antibody responses in the form of long-lived plasma cells and memory B cells. We found that T cell-deficient (T cell receptor β and δ chain [TCRβδ] knockout [KO]) mice persistently infected with polyomavirus (PyV) had long-lasting antiviral serum IgG, and we questioned whether they could generate TI B cell memory. TCRβδ KO mice did not form germinal centers after PyV infection, lacked long-lived IgG-secreting plasma cells in bone marrow, and did not have detectable memory B cell responses. Mice deficient in CD4+T cells had a lower persisting virus load than TCRβδ KO mice, and these mice had short-lived antiviral IgG responses, suggesting that a high virus load is required to activate naive B cells continuously, and maintain the long-lasting serum IgG levels. Developing B cells in bone marrow encounter high levels of viral antigens, which can cross-link both their B cell receptor (BCR) and Toll-like receptors (TLRs), and this dual engagement may lead to a loss of their tolerance. Consistent with this hypothesis, antiviral serum IgG levels were greatly diminished in TCRβδ KO/MyD88−/−mice. We conclude that high persisting antigen levels and innate signaling can lead to the maintenance of long-lasting IgG responses even in the absence of T cell help.IMPORTANCELifelong control of persistent virus infections is essential for host survival. Several members of the polyomavirus family are prevalent in humans, persisting at low levels in most people without clinical manifestations, but causing rare morbidity/mortality in the severely immune compromised. Studying the multiple mechanisms that control viral persistence in a mouse model, we previously found that murine polyomavirus (PyV) induces protective T cell-independent (TI) antiviral IgG. TI antibody (Ab) responses are usually short-lived, but T cell-deficient PyV-infected mice can live for many months. This study investigates how protective IgG is maintained under these circumstances and shows that these mice lack both forms of B cell memory, but they still have sustained antiviral IgG responses if they have high levels of persisting virus and intact MyD88-mediated pathways. These requirements may ensure life-saving protection against pathogens even in the absence of T cells, but they prevent the continuous generation of TI IgG against harmless antigens.

scholarly journals Outer Periarteriolar Lymphoid Sheath Arrest and Subsequent Differentiation of Both Naive and Tolerant Immunoglobulin Transgenic B Cells Is Determined by B Cell Receptor Occupancy

1997 ◽  
Vol 186 (5) ◽  
pp. 631-643 ◽  
Author(s):  
Matthew C. Cook ◽  
Antony Basten ◽  
Barbara Fazekas de St. Groth
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Receptor Occupancy ◽  
Cell Receptor ◽  
Antigen Concentration ◽  
Identical Manner ◽  
T Cell Help ◽  
Self Antigen

T-dependent B cell responses in the spleen are initiated in the outer periarteriolar lymphoid sheath (PALS) and culminate in the generation of proliferative foci and germinal center reactions. By pulsing anti–hen egg lysozyme (HEL) immunoglobulin transgenic (IgTg) B cells with various concentrations of HEL in vitro before adoptive transfer into normal recipients, it was shown that a critical number of B cell receptors (BCRs) must be ligated for B cells to undergo arrest in the outer PALS. T cell help was manipulated independently of the BCR stimulus by incubating B cells expressing the appropriate major histocompatibility complex class II antigen with a peptide recognized by CD4+ TCR Tg T cells. B cells which either failed to arrest in the outer PALS due to a subthreshold BCR stimulus, or arrested only transiently due to the brevity of the BCR stimulus, underwent an abortive response within the follicles when provided with T cell help. In contrast, naive B cells stimulated by a sustained, suprathreshold concentration of either foreign or self-antigen and given T cell help, proliferated in the outer PALS and then differentiated. Outer PALS arrest was not influenced by the nature of the B cells occupying the follicle, but appeared to be determined solely by the magnitude of BCR stimulation. Thus antigen-pulsed B cells arrested in the outer PALS in an identical manner irrespective of whether the follicles comprised a population of normal B cells with multiple specificities, a monoclonal naive population, or a monoclonal population of tolerant B cells. In addition, tolerant B cells were found to relocate from the follicles to the outer PALS of HEL/anti-HEL double Tg mice in which the concentration of soluble self-antigen had been increased by zinc feeding. Similarly, when anti-HEL Tg mice were crossed with a second HEL Tg strain expressing a higher concentration of soluble HEL, the tolerant anti-HEL Tg B cells were located constitutively in the outer PALS. Thus, subtle variations in antigen concentration resulted in dramatic changes in positioning of B cells within the spleen. A series of mixed bone marrow chimeras in which the effective antigen concentration was inversely related to the number of self-reactive B cells due to absorption of antigen by transgene-encoded membrane and secreted Ig, was used to confirm that alteration in B cell position previously attributed to changes in follicular composition could be explained on the basis of available antigen concentration, rather than the diversity of the repertoire.

scholarly journals Activation of Virus-specific Memory B Cells in the Absence of T Cell Help

2004 ◽  
Vol 199 (4) ◽  
pp. 593-602 ◽  
Author(s):  
Barbara J. Hebeis ◽  
Karin Klenovsek ◽  
Peter Rohwer ◽  
Uwe Ritter ◽  
Andrea Schneider ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cd4 T Cells ◽  
Plasma Cells ◽  
Human Herpesvirus ◽  
Memory B Cells ◽  
Specific Memory ◽  
T Cell Help

Humoral immunity is maintained by long-lived plasma cells, constitutively secreting antibodies, and nonsecreting resting memory B cells that are rapidly reactivated upon antigen encounter. The activation requirements for resting memory B cells, particularly the role of T helper cells, are unclear. To analyze the activation of memory B cells, mice were immunized with human cytomegalovirus, a complex human herpesvirus, and tick-born encephalitis virus, and a simple flavivirus. B cell populations devoid of Ig-secreting plasma cells were adoptively transferred into T and B cell–deficient RAG-1−/− mice. Antigenic stimulation 4–6 d after transfer of B cells resulted in rapid IgG production. The response was long lasting and strictly antigen specific, excluding polyclonal B cell activation. CD4+ T cells were not involved since (a) further depletion of CD4+ T cells in the recipient mice did not alter the antibody response and (b) recipient mice contained no detectable CD4+ T cells 90 d posttransfer. Memory B cells could not be activated by a soluble viral protein without T cell help. Transfer of memory B cells into immunocompetent animals indicated that presence of helper T cells did not enhance the memory B cell response. Therefore, our results indicate that activation of virus-specific memory B cells to secrete IgG is independent of cognate or bystander T cell help.

scholarly journals B cell receptor crosslinking can augment T cell help-mediated germinal center B cell selection

2018 ◽  
Author(s):  
Jackson S. Turner ◽  
Fang Ke ◽  
Irina L. Grigorova
Keyword(s):  
T Cell ◽  
B Cell ◽  
Germinal Center ◽  
Plasma Cells ◽  
Cell Receptor ◽  
Cell Selection ◽  
Antigenic Peptides ◽  
Follicular Helper ◽  
T Cell Help

AbstractSelection of germinal center (GC) B cells with B cell receptors (BCR) possessing high affinity to foreign antigen (Ag) and their differentiation into antibody-secreting long-lived plasma cells is critical for potent long-term humoral immunity. Ag-dependent engagement of GC B cell BCR triggers Ag internalization and loading of antigenic peptides on MHCII molecules for presentation to follicular helper T cells (Tfh) and acquisition of T cell help. However, whether it also provides signals that are critical or synergistic with T cell help for GC B cell selection and differentiation in vivo is not known. Here we show that T cell help is sufficient to induce GC B cell expansion and plasmablast (PB) formation in the absence of recurrent BCR engagement with Ag. Ag-mediated BCR crosslinking on the other hand is not sufficient to promote GC B cell selection, but can synergize with T cell help to enhance the GC B cell and PB responses when T cell help is limiting.

The different process of class switching and somatic hypermutation; a novel analysis by CD27− naive B cells

Blood ◽  
2002 ◽  
Vol 99 (2) ◽  
pp. 567-575 ◽  
Author(s):  
Haruo Nagumo ◽  
Kazunaga Agematsu ◽  
Norimoto Kobayashi ◽  
Koji Shinozaki ◽  
Sho Hokibara ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Messenger Rna ◽  
Plasma Cells ◽  
Somatic Hypermutation ◽  
Interleukin 2 ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
V Region

Abstract The relationship between class switch recombination (CSR) and somatic hypermutation has been unclear. By using human CD27− naive B cells, we investigated the somatic hypermutation and producibility of immunoglobulins (Igs) that occur after CSR. Although neither adult CD27− nor cord blood B cells, which showed the unmutated Ig V-region genes, produced IgG, IgM, or IgA in response to conventional stimuli, they produced IgG and IgM but not IgA in the presence of Staphylococcus aureus Cowan strain (SAC) + interleukin-2 (IL-2) + IL-10 + anti-CD40 mAb + CD32 transfectants (CD40/CD32T). The naive B cells also produced IgE when combined with IL-4 + CD40/CD32T. In parallel with IgG production, the expression of mature γ1 and γ 2 transcripts was induced from naive B cells by the stimuli. The CD27 expression on human naive B cells was induced remarkably by CD40 signaling or B-cell receptor engagement, but somatic hypermutation could not be induced. The proliferation and differentiation into plasma cells were induced from naive B cells, whereas most of the plasma cells displayed very low levels of mutations in Ig V-region genes. CD27− naive B cells expressed activation-induced cytidine deaminase messenger RNA by the stimuli later than CD27+memory B cells. Our results demonstrate that CSR, but not noticeable somatic hypermutation, can be induced from CD27− naive B cells upon B-cell receptor engagement and CD40 signaling in cooperation with cytokines, suggesting that CSR and somatic hypermutation processes can occur independently, and the antibodies produced in this in vitro system are low-affinity antibodies.

scholarly journals Optimized Protocols for in Vitro T Cell-Dependent and T Cell-Independent Activation for B Cell Differentiation Studies Using Limited Cells

2021 ◽  
Author(s):  
Casper Marsman ◽  
Dorit Verhoeven
Keyword(s):  
Cell Differentiation ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Plasma Cells ◽  
Cell Formation ◽  
B Cell Differentiation ◽  
Differentiation Potential ◽  
Human B Cell

Background/methods: For mechanistic studies, in vitro human B cell differentiation and generation of plasma cells are invaluable techniques. However, the heterogeneity of both T cell-dependent (TD) and T cell-independent (TI) stimuli and the disparity of culture conditions used in existing protocols makes interpretation of results challenging. The aim of the present study was to achieve the most optimal B cell differentiation conditions using isolated CD19+ B cells and PBMC cultures. We addressed multiple seeding densities, different durations of culturing and various combinations of TD stimuli and TI stimuli including B cell receptor (BCR) triggering. B cell expansion, proliferation and differentiation was analyzed after 6 and 9 days by measuring B cell proliferation and expansion, plasmablast and plasma cell formation and immunoglobulin (Ig) secretion. In addition, these conditions were extrapolated using cryopreserved cells and differentiation potential was compared. Results: This study demonstrates improved differentiation efficiency after 9 days of culturing for both B cell and PBMC cultures using CD40L and IL-21 as TD stimuli and 6 days for CpG and IL-2 as TI stimuli. We arrived at optimized protocols requiring 2500 and 25.000 B cells per culture well for TD and TI assays, respectively. The results of the PBMC cultures were highly comparable to the B cell cultures, which allows dismissal of additional B cell isolation steps prior to culturing. In these optimized TD conditions, the addition of anti-BCR showed little effect on phenotypic B cell differentiation, however it interferes with Ig secretion measurements. Addition of IL-4 to the TD stimuli showed significantly lower Ig secretion. The addition of BAFF to optimized TI conditions showed enhanced B cell differentiation and Ig secretion in B cell but not in PBMC cultures. With this approach, efficient B cell differentiation and Ig secretion was accomplished when starting from fresh or cryopreserved samples. Conclusion: Our methodology demonstrates optimized TD and TI stimulation protocols for more indepth analysis of B cell differentiation in primary human B cell and PBMC cultures while requiring low amounts of B cells, making them ideally suited for future clinical and research studies on B cell differentiation of patient samples from different cohorts of B cell-mediated diseases.

scholarly journals Signatures of B Cell Receptor Repertoire Following Pneumocystis Infection

2021 ◽  
Vol 12 ◽  
Author(s):  
Han Sun ◽  
Hu-Qin Yang ◽  
Kan Zhai ◽  
Zhao-Hui Tong
Keyword(s):  
B Cells ◽  
B Cell ◽  
Single Cell ◽  
Plasma Cells ◽  
Somatic Hypermutation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Receptor Repertoire ◽  
Elevated Expression ◽  
Pneumocystis Infection

B cells play vital roles in host defense against Pneumocystis infection. However, the features of the B cell receptor (BCR) repertoire in disease progression remain unclear. Here, we integrated single-cell RNA sequencing and single-cell BCR sequencing of immune cells from mouse lungs in an uninfected state and 1–4 weeks post-infection in order to illustrate the dynamic nature of B cell responses during Pneumocystis infection. We identified continuously increased plasma cells and an elevated ratio of (IgA + IgG) to (IgD + IgM) after infection. Moreover, Pneumocystis infection was associated with an increasing naïve B subset characterized by elevated expression of the transcription factor ATF3. The proportion of clonal expanded cells progressively increased, while BCR diversity decreased. Plasma cells exhibited higher levels of somatic hypermutation than naïve B cells. Biased usage of V(D)J genes was observed, and the usage frequency of IGHV9-3 rose. Overall, these results present a detailed atlas of B cell transcriptional changes and BCR repertoire features in the context of Pneumocystis infection, which provides valuable information for finding diagnostic biomarkers and developing potential immunotherapeutic targets.

scholarly journals Germinal center B cell development has distinctly regulated stages completed by disengagement from T cell help

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Ting-ting Zhang ◽  
David G Gonzalez ◽  
Christine M Cote ◽  
Steven M Kerfoot ◽  
Shaoli Deng ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
B Cell Differentiation ◽  
B Cell Maturation ◽  
Germinal Center B Cell ◽  
T Cell Help ◽  
Dose Dependent

To reconcile conflicting reports on the role of CD40 signaling in germinal center (GC) formation, we examined the earliest stages of murine GC B cell differentiation. Peri-follicular GC precursors first expressed intermediate levels of BCL6 while co-expressing the transcription factors RelB and IRF4, the latter known to repress Bcl6 transcription. Transition of GC precursors to the BCL6hi follicular state was associated with cell division, although the number of required cell divisions was immunogen dose dependent. Potentiating T cell help or CD40 signaling in these GC precursors actively repressed GC B cell maturation and diverted their fate towards plasmablast differentiation, whereas depletion of CD4+ T cells promoted this initial transition. Thus while CD40 signaling in B cells is necessary to generate the immediate precursors of GC B cells, transition to the BCL6hi follicular state is promoted by a regional and transient diminution of T cell help.

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