Foreign body reaction

A foreign body reaction (FBR) is a typical tissue response to a foreign body within biological tissue. It usually includes the formation of a foreign body granuloma. Tissue-encapsulation of an implant is an example, as is inflammation around a splinter. Foreign body granuloma formation consists of protein adsorption, macrophages, multinucleated foreign body giant cells (macrophage fusion), fibroblasts, and angiogenesis. It has also been proposed that the mechanical property of the interface between an implant and its surrounding tissues is critical for the host response.

In the long term, the foreign body reaction results in encapsulation of the foreign body within a calcified shell. For example, a lithopedion is a rare phenomenon which occurs most commonly when a fetus dies during an abdominal pregnancy, is too large to be reabsorbed by the body, and calcifies.