B220

B220 is the commonly used name for CD45R, a splice variant of the protein tyrosine phosphatase CD45 (Ptprc) in mice. The B220 designation traces to an approximate molecular weight of 220 kDa observed in early protein analyses. In murine immunology, B220 serves as a surface marker primarily associated with B lymphocytes.

Expression and role: CD45 family phosphatases regulate antigen receptor signaling. CD45R/B220 is widely expressed on developing and mature B cells in mice, from early bone marrow precursors to mature peripheral B cells. It is typically absent on plasma cells and on most T cells; plasmacytoid dendritic cells in mice commonly express B220 as well. B220 levels can vary with B cell maturation and activation, reflecting changes in signaling thresholds during development.

Applications: In flow cytometry and histology, B220 is used to identify B cell populations and, when combined with other markers such as IgM, IgD, and CD19, to define B cell subsets and developmental stages. It is also used in research on B cell signaling and development. In some genetic contexts, disruption of Ptprc affects B cell development and signaling, illustrating the functional importance of B220-containing isoforms.

Human relevance and limitations: The B220 designation is primarily used in mouse immunology; humans do not use the B220/CD45R label in the same way, and the CD45 isoform repertoire differs between species. When translating findings to humans, researchers rely on other CD45 isoforms and lineage markers.

See also: CD45, CD45R, Ptprc, B cell marker.