Blood-borne donor apoptotic cells are captured and presented to T cells by splenic CD11c^hi DCs.

A) PKH67-labeled BALB/c apoptotic cells were injected i.v. in B6 mice and the entrapment of blood-borne PKH-67⁺ (green) apoptotic cell fragments by splenic CD11c^hi CD45RA⁻ DCs (CD8α⁺ or CD8α⁻) and CD11c^int CD45RA⁺ pDCs was analyzed by FACS, 18 h later. B) WT and CD11c-DTR-eGFP B6 mice (both Thy1.2⁺) were reconstituted with CFSE-labeled 1H3.1 CD4 T cells (Thy1.1⁺), then treated (or not, control) with DT and injected i.v. with BALB/c apoptotic cells. Injection of DT in CD11c-DTR-eGFP mice deleted selectively CD11c^hi DCs and spared CD11c^int pDCs in the spleen (upper dot plots). In the absence of splenic pDCs, CD11c-DTR-eGFP mice were unable to present BALB/c apoptotic cell-derived allopeptides and induce proliferation of the adoptively transferred 1H3.1 CD4 T cells, evaluated 48 h later by CFSE-dilution by FACS-analysis (bottom dot plots). One representative out of 5 (in A) and 3 (in B) individual experiments is shown.