Fig. 3.

Flow cytometry and serological correlation of Duffy-negative and Duffy-positive phenotypes with respective genotypes in Malagasy school children from Tsiroanomandidy, Madagascar. (A) Flow cytometric analysis of Duffy blood group genotypes. Flow cytometry histograms show MFI that reflect binding of the Duffy antigen-specific anti-Fy6 antibody (NaM185-2C3) for one Malagasy genotyped as FY*B^ES/*B^ES [Fy(a−b−)] (red) and five well-characterized control donors who are FY*B^ES/*B^ES [Fy(a−b−)] (solid black), FY*B^ES/*X [Fy(a−b^weak)] (light green), FY*X/*X [Fy(a−b^weak)] (green), FY*A/*B^ES [Fy(a+b−)] (light blue), and FY*A/*B [Fy(a+b+)] (blue), respectively. Results include fluorescence of a Duffy-positive blood sample incubated with an isotype control antibody (dotted black line). (B) Flow cytometry of Duffy antigen expression on erythrocytes from 40 Malagasy study participants. Flow cytometry results show MFI that reflect binding of the Duffy antigen-specific anti-Fy6 antibody for 30 FY*B^ES/*B^ES [Fy(a−b−)] Malagasy samples (mean = 48, SD = 1.2), 6 FY*A/*B^ES [Fy(a+b−)] Malagasy samples (mean = 1,025, SD = 22.4), 2 FY*A/*A [Fy(a+b−)] Malagasy samples (mean = 1,937, SD = 54) and 2 FY*A/*B [Fy(a+b+)] Malagasy samples (mean = 1,896, SD = 8).