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- Al (-/-) mice exhibiteda reducedingestion of zymosan, Neisseria meningitidis or sheep red blood cells, when compared to Anx- Al+/+ 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 TNF alpha and IL- 6 was increased in Anx- A1(-/-) macrophages following phagocytosis of all types of particle.