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Quantitative modeling of the effect of antigen dosage on B-cell affinity distributions in maturating germinal centers.

ABSTRACT: Affinity maturation is a complex dynamical process allowing the immune system to generate antibodies capable of recognizing antigens. We introduce a model for the evolution of the distribution of affinities across the antibody population in germinal centers. The model is amenable to detailed mathematical analysis and gives insight on the mechanisms through which antigen availability controls the rate of maturation and the expansion of the antibody population. It is also capable, upon maximum-likelihood inference of the parameters, to reproduce accurately the distributions of affinities of IgG-secreting cells we measure in mice immunized against Tetanus Toxoid under largely varying conditions (antigen dosage, delay between injections). Both model and experiments show that the average population affinity depends non-monotonically on the antigen dosage. We show that combining quantitative modeling and statistical inference is a concrete way to investigate biological processes underlying affinity maturation (such as selection permissiveness), hardly accessible through measurements.

SUBMITTER: Molari M

PROVIDER: S-EPMC7360369 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Quantitative modeling of the effect of antigen dosage on B-cell affinity distributions in maturating germinal centers.

Molari Marco M Eyer Klaus K Baudry Jean J Cocco Simona S Monasson Rémi R

eLife 20200615

Affinity maturation is a complex dynamical process allowing the immune system to generate antibodies capable of recognizing antigens. We introduce a model for the evolution of the distribution of affinities across the antibody population in germinal centers. The model is amenable to detailed mathematical analysis and gives insight on the mechanisms through which antigen availability controls the rate of maturation and the expansion of the antibody population. It is also capable, upon maximum-lik ...[more]

PMID: 32538783

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Project description:Abstract: Epstein-Barr virus (EBV) infects germinal center (GC) B cells and establishes persistent infection in memory B cells. EBV-infected B cells sometimes cause B cell malignancies in humans with T- or NK-cell deficiency. We now find EBV-encoded Latent Membrane Protein 2A (LMP2A) to mimic B cell antigen receptor (BCR) signaling in murine GC B cells, causing altered humoral immune responses and autoimmune diseases. Investigation of the impact of LMP2A on B cell differentiation in mice that conditionally express LMP2A in GC B cells, or all B-lineage cells, found LMP2A expression enhanced not only BCR signals but also plasma-cell differentiation, in vitro and in vivo. Conditional LMP2A expression in GC B cells resulted in preferential selection of low-affinity antibody–producing B-cells despite apparently normal GC formation. GC B cell-specific LMP2A expression led to systemic lupus erythematosus-like autoimmune phenotypes in an age-dependent manner. Epigenetic profiling of LMP2A B cells found increased H3K27ac and H3K4me1 signals at the Zbtb20 locus. We conclude that LMP2A reduces the stringency of GC B cell selection and may contribute to persistent EBV infection and pathogenesis by providing GC B cells with pro-survival signals. Significance Statement: Epstein-Barr virus (EBV) is a human herpesvirus that establishes persistent infection of the B-cell compartment. EBV is associated with autoimmune diseases, including systemic lupus erythematosus (SLE). However, the molecular mechanisms by which EBV contributes to autoimmunity remain unclear. We used transgenic mouse models to study the role of EBV-encoded Latent membrane protein 2A (LMP2A), which mimics B-cell receptor signaling.　Interestingly, LMP2A not only enhanced B-cell survival, but also upregulated the transcription factor Zbtb20 and promoted plasma cell differentiation. When expressed late in B-cell development, LMP2A also caused prominent features of SLE, including autoantibody production with kidney immune complex deposition. Our findings suggest that LMP2A has important roles in B cell activation, differentiation and the development of EBV-associated autoimmune diseases.

Dataset Information

Quantitative modeling of the effect of antigen dosage on B-cell affinity distributions in maturating germinal centers.

Publications

Quantitative modeling of the effect of antigen dosage on B-cell affinity distributions in maturating germinal centers.

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