Fig 5. Immature CD71⁺ reticulocytes (retics) and non-phagocytosed Pv-IEs colocalise in specific splenic compartments.

The density and total biomass of CD71⁺ retics and non-phagocytosed Pv developmental stages (n = 6) were determined in the red-pulp SL, cords, PFZ, and white-pulp NCS (a). Non-phagocytosed Pv parasites were categorised into 3 groups (rings/trophozoites, schizonts, gametocytes), and a fourth group of those with unclassifiable stages. The cumulative distribution of CD71⁺ retics and Plasmodium developmental stages in the splenic architecture was calculated in individuals in whom intrasplenic parasites were visualised (b, left). The distribution of CD71⁺ retics in an uninfected spleen is also shown (b, right). In the splenic SL, a large proportion of CD71⁺ retics were apparently adherent to endothelial cells on the luminal side as observed by CD71 immunohistochemistry (c, left, representative image from Pv patient #4). The number of those apparently adherent (adh) and non-adherent (non-adh) were expressed as a percentage of red-pulp CD71⁺ retics in Pv as well as Pf, and compared as paired data (connected lines) using the Wilcoxon test (c, middle). The ratio of adherent-to-non-adherent CD71+ retics in the SL was compared between Pv and Pf using the Mann–Whitney test (c, right). A p-value <0.05 was considered significant. Data in a, b (left), and c (right) are individual datapoints with median and interquartile range. adh, adherent; NCS, non-circulatory space; non-adh, non-adherent; Pf, Plasmodium falciparum; PFZ, perifollicular zone; Pv, Plasmodium vivax; RBC, red blood cell; SL, sinus lumen.