The binding of pentraxins to apoptotic cells inhibits their phagocytosis by immature DCs.

(A) DCs derived from monocytes by culture with recombinant cytokines expressed CD1, MHC class II molecules, as well as CD40, CD80, and CD86 molecules as assessed by flow cytometry after staining with specific monoclonal antibodies (see “Materials and methods”). (B) DCs from different donors internalize fewer apoptotic cells (□) in the presence of PTX3 (50 μg/mL). On the contrary, no inhibition was observed in their ability to take up soluble FITC-ovalbumin (■). Uptake of apoptotic cells and antigens was assessed by flow cytometry (see “Materials and methods”). Results are expressed as percentage of inhibition calculated as follows: 100 − (% DCs that internalized pentraxin bound apoptotic cells/% DCs that internalized apoptotic cells) × 100.