Magnetic sorting of RBC-phagocytosing cells from the human spleen. The following assay was used to investigate erythrophagocytosis by cells of the human spleen in vitro. RBCs were biotinylated and coupled to magnetic beads. RBCs were opsonized and stained with the membrane dye DiD. Cells of the spleen were isolated and incubated with the RBCs for 1 hour. RBCs were lysed and the remaining spleen cells were put over a MACS column. Cells elutriated from the column were analyzed by flow cytometry and cytospin (original magnification ×50; May-Grünwald Giemsa stain).