The macrophage as target or obstacle in liposome-based targeting strategies

Macrophages can be found in all organs of the body. For that reason, the majority of liposomes, intended for drug- or antigen-targeting in vivo, will find macrophages on their way. Phagocytosis of the liposomes followed by disruption of their phospholipid bilayers and release of the entrapped molecules will be the consequence. This capability of macrophages may be an advantage when these cells themselves are forming the targets of the liposomes. However in most cases, the activity of macrophages has to be considered an obstacle for liposome-based targeting strategies. The positive and negative effects of macrophages on liposomes as drug- and antigen-carriers will be discussed.