The CD22 (HIB22) antibody recognizes a 130-140 kDa type-I transmembrane glycoprotein that is a B cell restricted antigen. CD22 antigen is e, Xenopus/Amphibian,pressed in the cytoplasm of pro-B and pre-B cells, and on the surface of mature B lymphocytes. CD22 e, Xenopus/Amphibian,pression is increased after activation and lost at the terminal stage of B cell differentiation. Most B cell leukemias and lymphomas also e, Xenopus/Amphibian,press CD22. It is not e, Xenopus/Amphibian,pressed in T cells,Mouse,onocytes and granulocytes. CD22 is an early marker for B-ALL and hairy-cell leukemia diagnostic. CD22 is an adhesion molecule that amplifies the signal of B cell activation. CD22 ligands are CD45RO antigen on T cells and CD75 antigen on B cells participating in the homotopic interaction of T and B cells.