Facts about the Duffy blood group system include:
- Duffy antigens reside on a glycoprotein that acts as a receptor for chemicals secreted by blood cells during inflammation.
- Antibodies can cause mild to severe transfusion reactions that are commonly delayed.
- Antigens are strongly expressed at birth and antibodies can cause mild Hemolytic Disease of the Fetus and Newborn (HDFN).
- Antigen binds Plasmodium vivax, the parasite that causes Malaria infection. RBCs that lack the Duffy antigens [Fy(a-b-)] are resistant to invasion by Plasmodium vivax.
- Fy null phenotype [Fy(a-b-)] is rare in Caucasians and Asians but found in 67% of people of African descent.
- Patients with Fy null can form Anti-Fy3 and Anti-Fy5. Both antibodies are resistant to enzyme treatment.
- Anti-Fy3 has been implicated in both acute and delayed transfusion reactions.
- Anti-Fy5 has been seen in delayed transfusion reactions.
- Fy(a-b-) phenotype is typically caused by the GATA mutation. The GATA mutation disrupts the binding site for RBC-specific GATA-1 transcription factor and prevents expression of the Fyb antigen on RBCs only. People with GATA mutation typically express Fyb on other cells in the body and do not make Anti-Fyb, and very rarely make Anti-Fy3 or Anti-Fy5.
Table 1. Duffy Blood Group System Facts.| Ag/Ab | Ag Frequency (White) | Ag Frequency (Black) | Dosage | Enzyme Interaction | Antibody Class* | Complement Binding | Clinically Significant |
| Fya | 65% | 10% | Yes | Destroyed by | IgG | No | Yes |
| Fyb | 80% | 23% | Yes | Destroyed by | IgG | No | Yes |
*IgG antibodies react best at 37°C and (generally) require anti-human globulin (AHG) to agglutinate.
Clinical significance relates to whether or not the antibody is capable of crossing the placenta to cause hemolytic disease of the fetus and newborn (HDFN) and/or hemolytic transfusion reactions (HTR). As a general rule, those antibodies that are considered clinically significant are IgG.
Dosage relates to the strength of reactions. An antibody that shows dosage will react stronger with a cell that is homozygous for the antigen it is binding to. Heterozygous cells demonstrate a weaker reaction.
