RBCs sensitized with anti-D IgG pretreated with EndoS are not attached to, or phagocytosed by, monocytes. (A) The degree of adherence/phagocytosis of RBCs sensitized with anti-D determined by monocyte monolayer assay and expressed as a number of monocytes with one or more adherent/phagocytosed RBCs of 100 monocytes detected. (B) The appearance of “rosettes” showed using Grünwald-Giemsa staining of monocyte monolayers incubated with RBCs sensitized with anti-D (top panel) and anti-D pretreated with EndoS (bottom panel; original magnification ×60). (C) Phagocytosis of sensitized RBCs by THP-1 cells and blood monocytes with or without treatment of anti-D with EndoS. The results are presented as the relative amount of internalized hemoglobin in cells detected by reactivity with 2,7-diaminofluorene. (D) Resuspended monocytes after incubation with RBCs sensitized with anti-D followed by the removal of noningested RBCs. (Left) RBCs sensitized with anti-D. (Right) Anti-D pretreated with EndoS. (E). Purified blood monocytes were incubated with FITC-labeled RBCs sensitized with anti-D and the degree of ingested RBCs determined by measuring the fluorescence.