Released in response to cellular activation, microvesicles are a major vector mechanism for the delivery of protein, nucleic acid and bioactive lipid payloads in local tissues and plasma. Large numbers of microvesicles (including those from neutrophils) are found within inflammatory sites, such as the rheumatoid synovium. Human neutrophil microvesicles promote tissue protection, and in some cases repair, by affecting function and phenotype of other inflammatory cells. Of these, tissue macrophages are central to the recovery of homeostasis after an inflammatory insult. The data herein indicate that microvesicles released by activated neutrophils impede lipopolysaccharide and interferon gamma-induced \M1-like" polarisation of macrophages via phosphatidylserine (PtdSer) exposure, and induce annexin A1-dependent release of transforming growth factor beta (TGFb). Macrophages treated with these vesicles stimulate the production of cartilage matrix from chondrocytes, and are unable to induce an inflammatory phenotype in fi broblasts. The efficacy of these vesicles is reproduced in two in vivo models of acute inflammation, zymosan-induced peritonits and K/BxN serum-transfer arthritis. Finally, the possibility of using both autologous, and cell-line-derived microvesicles as pharmacodynamic tools is explored. Microvesicles generated from neutrophils from patients with rheumatoid arthritis are found to be protective, and can outcompete the pro-inflammatory effects of both platelet microvesicles, and those isolated from synovial fluid of patients with rheumatoid arthritis. By building on the observation that anxA1 on microvesicles stimulates TGFb release in macrophages, a cell line was transfected to release anxA1+ microvesicles, and their e ects compared to those of their wild type counterparts.