Clone NaM16-4D3 , Decay-accelerating factor (DAF) is expressed on all cells in contact with serum, including all hematopoietic cells and the vascular endothelium. CD55 is expressed, like CD59, in erythrocytes, lymphocytes, monocytes, polymorphonuclear cells and platelets. CD55 is also expressed in non-hematopoietic tissues as well on epithelia in the gastrointestinal and genitourinary tracts and the central nervous system. A soluble form of CD55 is present in plasma and body fluids.
CD55 is a single chain Glycosylphosphatidylinositol (GPI) anchored glycoprotein. CD55 is often involved in the protection of cells from autologous compliment-mediated injury and are partially or completely lacking in peripheral blood cells. CD55 inhibits the formation and accelerates the decay of C3/C5 convertase complexes both of classical and alternative pathway. Since CD55 is well known membrane-associated complement regulator protein, like CD59, and present on all blood cells, CD55 and CD59 appear to be the most effective Mabs to detect very minor negative cell subsets (less than 1% on erythrocytes or less than 5% on PMN leukocytes).