Duffy The Vampire Slayer?

Duffy Null (Fya-Fyb-) and Malaria

 The prevailing thought was that Duffy negative (Fya-Fyb-) phenotypes typically found throughout the African population confer a level of immunity, protection, against Plasmodium vivax (and Plasmodium knowlesi) infection typically spread through Anopheles mosquito encounters.

 Nearly 75% of African descended humans have the Duffy negative phenotype Fya- Fyb-. Some populations and regions of Africa may have an even higher prevalence of such phenotype. The significance of this is...much like sickled cells are thought to provide protection against Plasmodium falciparum infection, lacking the Duffy antigen system is thought to provide protection against Plasmodium vivax infection, considering P. vivax uses the Duffy antigen system as a vector for infection.

 Duffy negative phenotype carriers (Fya-Fyb-) will typically carry a "silent" Fy-b allele. However, it does not get expressed on red blood cells due to a mutation that causes an encoding failure within the Erythroid Transcription Factor or "GATA-1". This produces a red cell that fails to carry and express the Fy-b antigen. It is highly unlikely that a patient would develop Anti-Fyb, because Fyb would still be expressed throughout other bodily tissues. Thus, the immune system recognizes the Fyb antigen as part of 'self'. For transfusion purposes, most transfusion centers would consider the patient to be Fyb positive *for transfusion purposes* and could receive Fyb positive blood. It is very unlikely the patient would mount a reaction to Fyb+ red cells. There is an even more rare mutation that does cause complete lack of Duffy antigen throughout the body

The Duffy antigen, known, wholly as DARC or Duffy Antigen Chemokine Receptor (shouldn't that be DACR then??) acts as a receptor for the parasite to invade the cell and begin the stages of infection. For decades of time it was believed this gave full protection over Plasmodium infection. Unfortunately, this is not the full case. As time went on and more studies are taken on, it is being noticed that Fya/Fyb patients do have Plasmodium infection. If anything, it appears there could be less severe infection with noticeable asymptomatic carriers of the disease in Duffy negative patients. It is possible that with time, Plasmodium will mutate further and cause considerably more damage in Duffy negative patients. 

More studies are still needing to look into this play between Duffy and Plasmodium. Don't try to load up on Duffy negative blood before traveling to endemic areas... that would be silly.