The tipping points in the initiation of B cell signalling: how small changes make big differences

Pierce, Susan K.; Liu, Wanli

doi:10.1038/nri2853

Cited by 163 publications

(201 citation statements)

References 83 publications

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“…Upon recognition of foreign Ags, the activation of B cells is initiated, which is subsequently linked to B cell proliferation and differentiation into plasma cells and memory B cells (1). B cells recognize the foreign Ags through their surface-expressed BCRs.…”

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confidence: 99%

B Cell Activation Is Regulated by the Stiffness Properties of the Substrate Presenting the Antigens

Wan

Zhang

Fan

et al. 2013

The Journal of Immunology

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109

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B lymphocytes are activated upon Ag sensing by BCRs. The substrate presenting the Ag can show different degrees of stiffness. It is not clear whether B cells can respond to changes in substrate stiffness. In this study we use high-resolution, high-speed live cell imaging techniques to capture the molecular events in B cell activation after the recognition of Ags tethered to polyacrylamide gel substrates with variable degrees of stiffness as quantified by Young’s modulus (2.6–22.1 kPa). We show that the initiation of B cell activation is extremely sensitive to substrate stiffness. B cells exhibit much stronger activation responses when encountering Ags tethered to substrates with a high degree of stiffness as measured by the accumulation of BCR, phospho-spleen tyrosine kinase, and phosphotyrosine molecules into the B cell immunological synapse. Ags tethered to stiff substrates induce the formation of more prominent BCR and phospho-spleen tyrosine kinase microclusters with significantly enhanced colocalization as compared with Ags tethered to soft substrates. Moreover, the expression of the B cell activation marker CD69 is enhanced in B cells encountering Ags on stiffer substrates. Through time-lapse live cell imaging, we find that the different responses of B cells to substrate stiffness are only demonstrated 5 min after BCR and Ag recognition. Using a series of cytoskeleton inhibitors, we determine that the mechanosensing ability of B cells is dependent on microtubules, and only mildly linked to the actin cytoskeleton. These results suggest the importance of the mechanical properties mediated by substrate stiffness in B cell activation.

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confidence: 99%

B Cell Activation Is Regulated by the Stiffness Properties of the Substrate Presenting the Antigens

Wan

Zhang

Fan

et al. 2013

The Journal of Immunology

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109

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“…Third, LC-F83 mutation can affect the biological activity of an antibody-antigen interaction through its modification of the Fab elbow angle and interdomain dynamics (47)(48)(49). Furthermore, B-cell signaling is sensitive to small conformational changes in the B-cell receptor (50). Modulation of the Fab elbow angle dynamics may have a favorable effect on B-cell receptor signaling (51).…”

Section: Discussionmentioning

confidence: 99%

Mutational landscape of antibody variable domains reveals a switch modulating the interdomain conformational dynamics and antigen binding

Koenig¹,

Lee²,

Walters³

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Somatic mutations within the antibody variable domains are critical to the immense capacity of the immune repertoire. Here, via a deep mutational scan, we dissect how mutations at all positions of the variable domains of a high-affinity anti-VEGF antibody G6.31 impact its antigen-binding function. The resulting mutational landscape demonstrates that large portions of antibody variable domain positions are open to mutation, and that beneficial mutations can be found throughout the variable domains. We determine the role of one antigen-distal light chain position 83, demonstrating that mutation at this site optimizes both antigen affinity and thermostability by modulating the interdomain conformational dynamics of the antigen-binding fragment. Furthermore, by analyzing a large number of human antibody sequences and structures, we demonstrate that somatic mutations occur frequently at position 83, with corresponding domain conformations observed for G6.31. Therefore, the modulation of interdomain dynamics represents an important mechanism during antibody maturation in vivo. Deciphering the molecular mechanism of SHMs in improving antibodies is critical for understanding the evolution of the immune repertoire. It is well recognized that mutations at the CDRs or FWR structurally adjacent to the CDRs can modulate and optimize the antigen-binding interface (4-7), and several studies have used saturated mutagenesis of CDR position to explore the effect of various mutations on affinity and specificity (8-11).The role of SHM in antigen-distal FWR is less well understood, however. Previous studies have suggested that the antigen-distal FWR contributes primarily to the variable domain structural integrity; thus, mutations at these positions would be either detrimental to or neutral for antigen-binding function (12)(13)(14). Other authors have characterized the potential of antigen-distal framework mutation as beneficial for antigen-binding function. For example, framework mutations can compensate for the destabilizing effect of mutations at CDRs needed for antigen binding (15). In other cases, non-CDR SHMs have been shown to be required for the neutralization activity of broadly neutralizing anti-HIV antibodies (16).Thus far, the roles of SHM have been studied primarily by examining the functional consequences of reverting the somatic mutation of selected antibodies back to the germline sequences (15-21). Although these studies have demonstrated that antibodies depend on somatic mutations to achieve high-affinity antigen binding, the approach is limited to the small set of mutations present in a given antibody.Here we took a systematic approach to assessing the mutability of the whole variable domain for maintaining or improving folding stability and antigen binding. We used a welloptimized anti-vascular endothelial cell growth factor (VEGF), G6.31, with high affinity (K d = 0.4 nM) and excellent thermostability [fragment antigen-binding (Fab) melting temperature (T m ) = 84°C]. G6.31 derives its HC and LC variable domains ...

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“…In vivo exposure to cognate antigens (in the form of reinfection or booster vaccination) results in the activation of memory B cells and their subsequent proliferation and differentiation into antibody-secreting daughter cells. 21,22 To assess whether the impaired B-cell proliferation could affect the capacity of memory B cells to differentiate into ASCs, we measured the in vitro differentiation of total PBMCs after stimulation with PWM and CpG alone or in combination (Fig 4, A).…”

Section: Impaired Proliferation Is Associated With Lower Frequencies mentioning

confidence: 99%

Defective B-cell proliferation and maintenance of long-term memory in patients with chronic granulomatous disease

Cotugno

Finocchi

Cagigi

et al. 2015

Journal of Allergy and Clinical Immunology

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Background: Chronic granulomatous disease (CGD) is a primary immune deficiency characterized by a defect in reactive oxygen species production. Although the effect of CGD mainly reflects on the phagocytic compartment, B-cell responses are also impaired in patients with CGD. Objective: We sought to investigate how defective gp91 phox expression in patients with CGD and CGD carriers might affect the B-cell compartment and maintenance of long-term memory. Methods: We studied the B-cell compartment of patients with CGD in terms of phenotype and ability to produce reactive oxygen species and proliferate on stimuli differently directed to the B-cell receptor and Toll-like receptor 9. We further studied their capacity to maintain long-term memory by measuring cellular and serologic responses to measles. Results: We show that the memory B-cell compartment is impaired among patients with CGD, as indicated by reduced total (CD19 1 CD27 1 ) and resting (CD19 1 CD27 1 CD21 1 ) memory B cells in parallel to increased naive (CD19 1 CD27 2 IgD 1 ) B-cell frequencies. Data on CGD carriers reveal that such alterations are related to gp91 phox expression. Moreover, proliferative capabilities of B cells on selective in vitro stimulation of B-cell receptor or Toll-like receptor 9 pathways were reduced in patients with CGD compared with those seen in age-matched healthy control subjects. Significantly lower measles-specific antibody levels and antibody-secreting

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The tipping points in the initiation of B cell signalling: how small changes make big differences

Cited by 163 publications

References 83 publications

B Cell Activation Is Regulated by the Stiffness Properties of the Substrate Presenting the Antigens

B Cell Activation Is Regulated by the Stiffness Properties of the Substrate Presenting the Antigens

Mutational landscape of antibody variable domains reveals a switch modulating the interdomain conformational dynamics and antigen binding

Defective B-cell proliferation and maintenance of long-term memory in patients with chronic granulomatous disease

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