CD20 as a gatekeeper of the resting state of human B cells
Kathrin Kläsener1,2,3, Julia Jellusova1,2,3,4, Geoffroy Andrieux5,6
1Biology III, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
Insights
CD20 regulates B cell receptor organization and activation. Loss or targeting of CD20 disrupts B cell function, leading to altered cell fate and potential plasma cell development.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- CD20 is a B cell-specific protein targeted by therapeutic antibodies.
- The precise biological function of CD20 in B cells remains largely unknown.
- Understanding CD20's role is crucial for optimizing B cell depletion therapies.
Purpose of the Study:
- To elucidate the biological function of CD20 in resting B lymphocytes.
- To investigate the impact of CD20 ablation or anti-CD20 antibody treatment on B cell nanoscale receptor organization and activation.
- To determine the downstream effects of CD20 disruption on B cell fate and differentiation.
Main Methods:
- CRISPR/Cas9-mediated CD20 gene ablation in B cells.
- Analysis of B cell antigen receptor and CD19 co-localization using nanoscale imaging.
- Assessment of B cell activation markers and surface protein expression.
- Investigation of transcriptional changes (PAX5 to BLIMP-1) and metabolic reprogramming.
- Treatment of B cells with anti-CD20 antibody rituximab in vitro and in vivo.
Main Results:
- CD20 ablation caused B cell antigen receptor and CD19 relocalization, leading to transient B cell activation and surface marker internalization.
- Reintroducing CD20 restored normal B cell surface protein expression and resting state.
- Rituximab treatment induced similar nanoscale receptor rearrangements and transient activation.
- CD20-deficient B cells exhibited a loss of identity, transcriptional switch, metabolic shift, and progressed towards plasma cell differentiation.
Conclusions:
- CD20 is essential for maintaining the nanoscale organization of B cell surface receptors in resting B lymphocytes.
- Engagement or loss of CD20 triggers significant alterations in B cell membrane organization, leading to transient activation and profound changes in cell fate.
- These findings reveal a novel mechanism by which CD20 controls B cell homeostasis and differentiation, impacting therapeutic strategies.
Abstract:
CD20 is a B cell-specific membrane protein and represents an attractive target for therapeutic antibodies. Despite widespread usage of anti-CD20 antibodies for B cell depletion therapies, the biological function of their target remains unclear. Here, we demonstrate that CD20 controls the nanoscale organization of receptors on the surface of resting B lymphocytes. CRISPR/Cas9-mediated ablation of CD20 in resting B cells resulted in relocalization and interaction of the IgM-class B cell antigen receptor with the coreceptor CD19. This receptor rearrangement led to a transient activation of B cells, accompanied by the internalization of many B cell surface marker proteins. Reexpression of CD20 restored the expression of the B cell surface proteins and the resting state of Ramos B cells. Similarly, treatment of Ramos or naive human B cells with the anti-CD20 antibody rituximab induced nanoscale receptor rearrangements and transient B cell activation in vitro and in vivo. A departure from the resting B cell state followed by the loss of B cell identity of CD20-deficient Ramos B cells was accompanied by a PAX5 to BLIMP-1 transcriptional switch, metabolic reprogramming toward oxidative phosphorylation, and a shift toward plasma cell development. Thus, anti-CD20 engagement or the loss of CD20 disrupts membrane organization, profoundly altering the fate of human B cells.
Related Concept Videos
01:24B Cell Activation and Differentiation
When naive B cells encounter a specific antigen that can bind to the B cell receptor (BCR) on their surface, they undergo sensitization to respond to the antigen's presence. Sensitization begins with...
01:22T Cell Activation and Clonal Selection
Naive T cells that have not yet encountered an antigen express two primary CD...
01:23Cells of the Adaptive Immune Response
01:28Diversity of Antigen Receptors
Before encountering any antigen, lymphocytes express these receptors. On B cells, the antigen receptor is a membrane-bound antibody molecule called BCR; on T cells, it is a T cell receptor or TCR. B and T cell receptors are composed of two...
01:40Cell-mediated Immune Responses
01:18Lymphoid Cells and Tissues
Lymphoid cells consist of various types of immune system cells. These include B and T lymphocytes, which are responsible for producing antibodies and killing infected cells, respectively. Dendritic cells act as messengers between the innate and adaptive...