Decay-accelerating factor (CD55) deficiency

Gene Information


HUGO name: CD55


  • DAF
  • CR
  • TC
  • decay accelerating factor for complement
  • Complement decay-accelerating factor precursor
  • CD55 antigen


Reference sequences

Chromosomal location


Protein Information


Protein function:

This protein recognizes C4b and C3b fragments that condense with cell-surface hydroxyl or amino groups when nascent C4b and C3b are locally generated during C4 and C3 activation. Interaction of DAF with cell-associated C4b and C3b polypeptides interferes with their ability to catalyze the conversion of C2 and factor B to enzymatically active C2a and bb and thereby prevents the formation of C4b2a and C3bbb, the amplification convertases of the complement cascade.


Monomer (major form) and non-disulfide-linked, covalent homodimer (minor form).

Subcellular location:

Attached to the membrane by a GPI-anchor.

Post-translational modification:

The SER/THR-rich domain is heavily o-glycosylated.

Alternative products:

2 isoforms; 1/DAF-1 and 2/DAF-2; are produced by alternative splicing.


DAF is responsible for the cromer blood group system. It consists of at least seven high-incidence (cr(a), tc(a), dr(a), es(a), wes(b), umc, and ifc) and low-incidence (tc(b), tc(c), and wes(a)) antigens that reside on DAF. In the cromer phenotypes dr(a-) and inab there is reduced or absent expression of DAF, respectively. In the case of the dr(a-) phenotype, a single nucleotide substitution within exon 5 accounts for two changes: a simple amino acid substitution that is the basis of the antigenic variation, and an alternative splicing event that underlies the decreased expression of daf in this phenotype.


Expression pattern for human

Tissue Expression (%) Clones
nose, olfactory epithelium 7.34 1:1116
muscle (skeletal) 6.85 8:9571
mammary gland 5.68 1:1441
cervix 5.50 17:25325
leukopheresis 5.39 3:4557
pancreas, exocrine 5.35 14:21418
bone marrow 4.95 12:19854
placenta 4.32 49:92983
lung 3.89 74:155782
gall bladder 3.36 1:2435