CD44 is a glycosylated cartilage-linked protein. The protein exists in a variety of forms with different molecular structures, ranging from 85 kDa to 250 kDa. It is a multistructural and multifunctional cell surface molecule and involved in various biological processes such as cell proliferation, cell differentiation, cell migration, angiogenesis, presentation of cytokines, chemokines, and growth factors to the corresponding receptors, and docking of proteases at the cell membrane, as well as in signaling for cell survival. Although all the activities are related to normal cell, but it has also some pathologic activities of cancer cells.
The CD44 antigen is expressed on a variety of cell types including peripheral blood leukocytes (B and T lymphocytes, monocytes, granuloctes) and red cells. It is also weakly expressed on platelets. The antibody is also reactive with bone marrow nucleated cells, medullary thymocytes, liver Kupffer cells, fibroblasts, corneal cells, epidermal keratinocytes, synovial cells, a subset of pancreatic acinar cells and brain cells. The epitope recognized by this clone is sensitive to formalin fixation and paraffin embedding.
