CD55 is expressed on the surface of erythrocytes and most splenic leukocytes, including B and T lymph ocytes and CD11b-positive splenocytes,but it is not detected on thymocytes.Immunohistochemical staining (using a different monoclonal antibody) demonstrates that CD55 is expressed on vascular endothelium and many other cells types in a wide variety of organs.In the mouse, there are two isoforms of CD55, transmembrane and GPI-anchored, that are recognized by the RIKO-5 antibody.Both isoforms are able to protect cells from complement attack by inhibiting the deposition of C3 on antibody-sensitized cells,but the RIKO-5 antibody is not able to neutralize this activity. CD97, a member of the EGF-TM7 family that is widely expressed in mouse tissues, is another ligand for CD55.
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DAF, decay-accelerating factor
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65 kD
