Complement<unk> , also known as CD55 or<unk> , is a protein that, in humans, is encoded by the CD55 gene.<unk>  regulates the complement system on the cell surface. It recognizes C4b and C3b fragments that are created during activation of C4 (classical or lectin pathway) or C3 (alternative pathway). Interaction of<unk>  with cell-associated C4b of the classical and lectin pathways interferes with the conversion of C2 to C2b, thereby preventing formation of the C4b2a C3-convertase, and interaction of<unk>  with C3b of the alternative pathway interferes with the conversion of<unk>  B to Bb by<unk>  D, thereby preventing formation of the C3bBb C3 convertase of the alternative pathway. Thus, by limiting the amplification convertases of the complement cascade,<unk>  indirectly blocks the formation of the membrane attack complex. This glycoprotein is broadly distributed among hematopoietic and non-hematopoietic cells. It is a determinant for the Cromer blood group system.
Decay-accelerating factor
Lupus anticoagulant
Therapeutic interfering particle
Precipitin
Fragment crystallizable region
Serpin
Haptocorrin
Autoantibody