Blockade of CD47 with SIRPαFc (TTI-621) promotes phagocytosis of Sézary cells but not nonmalignant CD4⁺cells. (A) Cytospin preparation of representative samples 2 hours after phagocytosis in the presence of an IgG1 isotype control molecule (TTI-402) or TTI-621. Red arrows identify Sézary cells that are external to macrophages in the presence of isotype control but phagocytosed in the presence of TTI-621 (Romanowsky stain; original magnification ×100). (B) Macrophage-mediated phagocytosis of matched nonmalignant (blue) or Sézary cells (red) from 8 patients with SS in media (no treatment), 1 µM TTI-403 (isotype control), and 1 µM TTI-621. One-way analysis of variance with Tukey posttest (*P < .05; **P < .01).