Table 2-23. Phenotypes and frequencies in the Duffy system.
Table 2-24. Serologic behavior of the common Duffy system antibodies.
c. Other antigens in this system have been described:
(1) Fy3. An antibody found in serum of one of the rare, White Fy(a-b-)
individuals, anti-Fy3, reacts with all Fy(a+) and Fy(b+) but not Fy(a-b-) cell samples. Its
apparent anti-Fya + anti-Fyb specificities cannot be separated by absorption. Unlike
anti-Fya and -Fyb, anti-Fy3 reacts strongly with enzyme-treated red blood cells and
probably detects a determinant distinct from either Fya or Fyb.
(2) Fy4. An antibody also enhanced by proteolytic enzymes was found in
an Fy(a+b+) Black subject whose serum reacted with all Fy(a-b-) red blood cells from
Blacks, some Fy(a+b-) and Fy(a-b+) red blood cells, but not with Fy(a+b+) cells. The
gene corresponding to Fy4 was previously called Fy, being common in Blacks (68% of
Blacks are Fy(a-b-)).
(3) Fy5. Anti-Fy5, found in the serum of a transfused Black Fy(a-b-) boy,
reacted with Fy(a+) or Fy(b+) cells of common Rh type but not with Fy(a-b-) cells from
Blacks, nor with Rhnull cells. Apart from the aberrant reactions with Rhnull cells, anti-Fy5
closely resembles anti-Fy3. The loci for both Duffy and Rh systems are on chromosome one.