Related Experiment Video
Updated: Aug 9, 2026
Analysis of Cell Cycle Position in Mammalian Cells
Published on: January 21, 2012
Transitional and marginal zone B cells have a high proportion of unmasked CD22: implications for BCR signaling
Claus-Peter Danzer1, Brian E Collins, Ola Blixt
1Institute of Virology and Immunobiology, University of Würzburg, Versbacherstrasse 7, 97078 Würzburg, Germany.
Insights
Unmasked CD22 (Cluster of Differentiation 22) on B cells indicates activation. This unmasking is more prevalent in transitional, marginal zone, and B1 cells, suggesting a role in immune cell development and signaling thresholds.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- CD22 is a B cell-specific Siglec family member that inhibits B cell receptor (BCR) signaling.
- CD22 binds alpha2,6-linked sialic acids via its first Ig-like domain.
- CD22 can bind ligands in trans (to other cells) or in cis (to its own cell surface), with cis-binding enhancing inhibitory function.
Purpose of the Study:
- To investigate the binding status of CD22 ligands on B cells.
- To characterize B cell subpopulations with unbound (unmasked) CD22.
- To explore the functional implications of CD22 unmasking in B cell development and activation.
Main Methods:
- Utilized a novel oligomeric streptavidin-based sialylated probe as an artificial CD22 ligand.
- Analyzed CD22 binding status on various B cell populations.
- Correlated CD22 unmasking with B cell phenotype and activation markers.
Main Results:
- Most B cells exhibit CD22 bound to endogenous ligands in cis.
- A subpopulation of B cells displays unmasked CD22.
- Unmasked CD22 is significantly increased (2-fold) in transitional, marginal zone, and peritoneal B1 cells compared to mature B cells.
- B cells with unmasked CD22 present an activated phenotype.
Conclusions:
- CD22 unmasking is observed in specific B cell subsets and correlates with an activated phenotype.
- Unmasking may lower the signaling threshold at developmental checkpoints (e.g., transitional B cells) or result from activation processes.
- This finding provides insights into B cell regulation and activation dynamics.
Abstract:
CD22, a B cell-specific member of the Siglec family, is an important inhibitor of B cell signaling. The first Ig-like domain of CD22 specifically binds to alpha2,6-linked sialic acids. Through these interactions CD22 can mediate adhesion to other cells in trans, but can also bind endogenous ligands on the B cell surface in cis. Cis binding of CD22 to sialylated ligands enhances the efficiency of inhibition and thereby reduces the BCR signaling strength. In this study we used a newly developed oligomeric streptavidin-based sialylated probe as an artificial CD22 ligand. We found that CD22 is bound to ligands in cis on most B cells. However, there is a proportion of B cells with unbound (unmasked) CD22. The subpopulation with unmasked CD22 is 2-fold increased in transitional and marginal zone B cells in the spleen and on B1 cells in the peritoneum, when compared to mature B cells. Also, B cells with unmasked CD22 have an activated phenotype. Unmasking of CD22 could be functionally involved in lowering the signaling threshold on developmental checkpoints such as transitional B cells and during B cell activation or could be a consequence of such activation processes.
Related Concept Videos
01:22T Cell Activation and Clonal Selection
Naive T cells that have not yet encountered an antigen express two primary CD...
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...