P cynomolgi RBC tropism and specificity for DARC. (A-B) Invasion efficiencies of P cynomolgi into macaque or human RBCs, reticulocytes, and normocytes (CD71^–). Two representative photomicrographs of P cynomolgi invasions in monkey normocytes and human reticulocytes (scale bar = 20 μm). The invasion data were derived from 8 independent experiments, and significance was determined by one-way analysis of variance (ANOVA) and post hoc analysis. (C) Inhibition of P cynomolgi invasion by enzymatic treatment of RBCs. (D) Inhibition of macaque or human RBC invasion by anti-Fy6 (2C3 antibody) or anti-FyB. (E) In-depth analysis of inhibition of macaque RBC invasion by anti-Fy6 (2C3 antibody), anti-FyB, or the chemokine IL-8. (F) The extracellular domain 1 (ECD1) of DARC showing the region targeted by IL-8 and the antibodies and used in this study. Residues in red represent the 2C3 antibody recognition region, with the key binding residues marked by an asterisk; residues in green represent the position of the Fy group (FyB in macaque, G D); residues in yellow indicate the IL-8 binding sites.²⁶  (G) Alignment of partial sequences of DARC from 5 of the monkey donors (D1-5) used in this study. The color notations correspond to the ECD1 diagram of DARC. *P < .05; ***P < .001. n.s., nonsignificant.