Duffy blood group antigens: structure, serological properties and function

Duffy (Fy) blood group antigens are located on seven-transmembrane glycoprotein expressed on erythrocytes and endothelial cells, which acts as atypical chemokine receptor (ACKR1) and malarial receptor. The biological role of the Duffy glycoprotein has not been explained yet. It is suggested that Duffy protein modulate the intensity of the inflammatory response. The Duffy blood group system consists of two major antigens, Fy(a) and Fy(b), encoded by two codominant alleles designated FY*A and FY*B which differ by a single nucleotide polymorphism (SNP) at position 125G>A of the FY gene that results in Gly42Asp amino acid change in the Fy(a) and Fy(b) antigens, respectively. The presence of antigen Fy(a) and/or Fy(b) on the erythrocytes determine three Duffy-positive phenotypes: Fy(a+b-), Fy(a-b+) and Fy(a+b+), identified in Caucasian population. The Duffy-negative phenotype Fy(a-b-), frequent in Africans, but very rare in Caucasians, is defined by the homozygous state of FY*B-33 alleles. The FY*B-33 allele is associated with a SNP -33T>C in the promoter region of the FY gene, which suppresses erythroid expression of this gene without affecting its expression in other tissues. The FY*X allele, found in Caucasians, is correlated with weak expression of Fy(b) antigen. Fy(x) antigen differs from the native Fy(b) by the Arg89Cys and Ala100Thr amino acid substitutions due to SNPs: 265C>T and 298G>A in FY*B allele. The frequency of the FY alleles shows marked geographic disparities, the FY*B-33 allele is predominant in Africans, the FY*B in Caucasians, while the FY*A allele is dominant in Asians and it is the most prevalent allele globally.