Resolving the heterogeneity of human nascent reticulocytes. (A) Gating strategy using CD71 and SYTO16 as surface markers. (B) Four populations of reticulocytes (R1-R4) can be isolated and sorted based on the 2 surface markers. (C) Morphology of sorted reticulocyte populations by phase contrast microscopy (left panels), and immunofluorescence (right panels). (D) Transmission electron microscopy of a nascent reticulocyte highlighting numerous ruffles and organelles.