Anti-Mouse CD45R (B220) Antibody

The RA3-6B2 antibody reacts with an epitope on the extracellular domain of the exon A‐restricted isoform of mouse CD45. CD45 is a member of the protein tyrosine phosphatase family and functions in a number of immunoregulatory processes, including cell activation, growth, differentiation, and oncogenic transformation. The large cytoplasmic portion of CD45 contains two tyrosine phosphatase domains (one of which is enzymatically active) that are involved in modulating the function of Src kinases such as Lck and Fyn. Several isoforms of CD45 have been identified, the expression of which differs according to cell type and functional status. Alternative splicing of three exons encoding the extracellular RA, RB, and RC polypeptide sequences gives rise to up to 8 isoforms with molecular masses in the range of 200 - 220 kDa. The exon A‐restricted isoform of mouse CD45, termed CD45R, contains the RA, RB, and RC regions and is the largest of the isoforms. CD45R is expressed by the B cell lineage from early pro‐B to mature B cells, with its expression downregulated during differentiation to plasma cells. CD45R is also expressed on subsets of T, NK, dendritic, and lymphokine-activated killer (LAK) cells.