Clusters of Differentiation (CD) proteins are a group of cell surface markers that can be used to identify different stages of B cell development or activation, including progenitor B cells, pro-B cells, pre-B cells, immature B cells, transitional 1 B cells, transitional 2 B cells, marginal zone B cells, na?ve mature follicular B cells, activated germinal center B cells, memory B cells, plasmablast cells, and plasma cells. Other cell surface markers used to identify specific stages of B cell development or activation are also listed.
For example, CD138 distinguishes circulating plasmablasts and plasma cells, from other developmental and functional subsets. The key marker for B-cell panels is the lineage marker CD19, which is expressed by almost all cells belonging to the B-cell lineage. In the mouse, CD45R/B220 is traditionally used. Depending on the type of sample that is being analyzed, different markers can be selected to define the specific B-cell subsets of interest. The example shown analyzes human peripheral blood using CD19, CD20, IgD, CD27, CD38, and CD24. Adding activation markers (CD69, CD25, CD80, CD86) can inform about which subsets are activated, and provide important clues about an individual's immune response.