Collectins, such as surfactant protein D (SP-D), bind apoptotic cells; however, the ligands that they recognize on these cells are unknown. We hypothesized that SP-D binds to the DNA present on these cells. We show that SP-D binds and aggregates mouse alveolar macrophage DNA effectively. Alveolar macrophages of SP-D((-/-)) mice contained more nicked DNA than those of SP-A((-/-)) and wild type mice. Our results also suggest that carbohydrate recognition domains of SP-D may recognize DNA present on the apoptotic cells. Therefore, cell-surface DNA could be a ligand for recognition of apoptotic cells by collectins.