Kinetics and morphologic aspects of pitting. EMIF-positive iRBCs (EMIF⁺-iRBC) (Ai) were distinguished from once-infected RBCs (O-iRBC, Aii arrow) by the presence of intraerythrocytic Hoechst-labeled dead parasite remnants (DPRs). The proportion of O-iRBCs in the perfusate increased during experiments (Aiii-iv). On Giemsa-stained histologic sections, uninfected RBCs were observed as they squeezed to cross the sinus walls (Bi-ii) from cords (co) to sinus lumens (sl). During pitting of Art-iRBCs, small DPRs were left on the cordal side of the sinus wall—a typical aspect of the pitting process (Ci-iii)—whereas large DPRs had a bispherical cordal-luminal aspect (Di). Some DPRs retained in the sinus wall were still linked to their once-host cell by a string-like formation (Dii) and incompletely pitted Art-iRBCs were observed in sinus lumens, with a membrane-bound DPR in contact with a luminal cell (Diii-iv). (E) Aspect of pitting as observed by immunochemistry using a human convalescent serum, the Ig being detected by alkaline-phosphatase labeled reagent.