Impaired phagocytic mechanism in annexin 1 null macrophages

1 The role of the anti-inflammatory protein annexin-A1 (Anx-A1) in the phagocytic process has been investigated using a murine bone marrow culture-derived macrophage model from Anx-A1 ^+/+ and Anx-A1 ^-/- mice. 2 Macrophages prepared from Anx-A1 ^-/- mice exhibited a reduced ingestion of zymosan, Neisseria meningitidis or sheep red blood cells, when compared to Anx-A1 ^+/+ cells and in the case of zymosan this effect was also mirrored by a reduced clearance in vivo when particles were injected into the peritoneal cavity of Anx-A1 ^-/- mice. 3 The ablation of the Anx-A1 gene did not cause any apparent cytoskeletal defects associated with particle ingestion but the cell surface expression of the key adhesion molecule CD11b was depressed in the Anx-A1 ^-/- cells providing a possible explanation for the attenuated phagocytic potential of these cells. 4 The production of the cytokines TNFα and IL-6 was increased in Anx-A1 ^-/- macrophages following phagocytosis of all types of particle.