SURFIN accumulates within the parasitophorous vacuole in late schizonts and is associated with released merozoites. (A) Alexa 488–labeled SURFIN4.2 (green) detected with anti-S1.3 antibodies in parasites developing from late trophozoite stage to schizonts. PI staining (red) was used to visualize nuclei. (B–D) SURFIN4.2 was found localized in MAM and the PM of late and bursting schizonts (48 h), and associated with the released merozoite surface. Dashed circles indicate the area of the IE. (B) IFA with anti-S1.3 + PI on bursting schizonts. IFA (anti-rSURFIN4.2) and immunoelectron microscopy (anti-S1.4 Ig) on late schizonts (C) and released merozoites (D). SURFIN associated with PM or merozoite-associated material is indicated by arrows. (E) SURFIN4.2 did not colocalize with the microneme AMA-1. A detailed analysis of SURFIN4.2 (anti-S1.3 antibodies) and AMA-1 in relation to the nuclei and to each other in merozoites is shown. (B and E) A schematic representation of the antigen localization is shown on the right. Bars: IFA, 2 mm; EM, 0.5 mm.

Winter G, Kawai S, Haeggström M, Kaneko O, von Euler A, Kawazu S, Palm D, Fernandez V, Wahlgren M. SURFIN is a polymorphic antigen expressed on Plasmodium falciparum merozoites and infected erythrocytes. J Exp Med. 2005 201:1853-63.