The clone MYG13 recognizes CD22 cell surface antigen, a 130-140kDa protein. The expression of CD22 is primarily restricted to the normal and neoplastic B cells but does not express on other hematopoietic cells. The initiation of expression of CD22 starts in the cytoplasm of pro-B and pre-B cells. Although CD22 is not expressed by plasma cells, it is abundantly expressed by the follicular mantle and marginal zone B-cells. Being a member of the immunoglobulin superfamily, CD22 serves as an adhesion receptor for sialic acid-bearing ligands expressed on erythrocytes and leukocytes. The role of CD22 in the activation of B-cells is primarily associated with tyrosine kinases mediated signal transduction pathways.