Background：CD53 is a 35-42 kD type III tetraspan membrane protein. It is expressed on all leukocytes, but not on platelets or erythrocytes. CD53 is thought to be involved in signal transduction. It has been shown to interact with a number of proteins including IL-4, CD20, CD2, CD9, IL-2, VLA-4, and CD4. Cross-linking of CD53 promotes B cell activation. The CD53 antigen is highly glycosylated and treatment with endoglycosidase F reduces the apparent molecular weight of this protein by approximately 25 kD.
