Uptake of apoptotic cells by splenic DCs in vivo.

Internalization of apoptotic cells by splenic DCs was analyzed in cytospins of immunobead-sorted DCs 1 hour after injection of PKH67-(green) apoptotic (BALB/c) splenocytes in (B10) mice. (A) CD11c⁺ DCs with apoptotic cell fragments (green) and with DAPI⁺ intracytoplasmic inclusions, likely DNA from ingested apoptotic cells (in blue indicated by arrow in inset). (B) Serial sections analyzed by confocal microscopy confirmed the intracellular localization of PKH67⁺ fragments in splenic CD11c⁺ DCs. (C) The donor origin (BALB/c) of the intracytoplasmic inclusions in (B10) DCs was confirmed by H2D^d expression (in red) in PKH67⁺ (green) fragments. (D-E) FITC-TUNEL staining in combination with Cy3–anti-CD11c or Cy3–anti-H2D^d confirmed the presence of donor (BALB/c)-derived apoptotic cells within (B10) DCs. (F-J) One hour after intravenous injection of apoptotic cells, DCs that internalized apoptotic cells were CD11b^hi, F4/80^lo/−, CD8α⁻, MOMA-1⁻, or ER-TR9⁻. Images are representative of 5 animals analyzed. Nuclei were counterstained with DAPI. Original magnification for all panels, × 1000; inset A, × 1000.