Macrophages: Frustrated Phagocytic Analysis

Macrophage responses to foreign material may be size and geometry dependent. Macrophages are master phagocytic cells which scour the body for foreign materials that they phagocytize and destroy. Naturally, macrophages can effectively phagocytize materials which are less than 10 μm. When material size increases (10-100 μm) single macrophages can no longer phagocytize them, instead a giant multinucleated cell called a foreign body giant cell is formed from the fusion of several macrophages in an attempt to phagocytize the material (Anderson et al. 2008). When materials are even larger (bulk implants >100 μm), macrophages undergo fusion and frustrated phagocytosis. At this level, it is understood that thickness may also modulate responses, where the thicker the material, the greater the foreign body and fibrotic responses expected (Nichols et al. 2013; Helton et al. 2011; Ward et al. 2002). Frustrated phagocytosis leads to highly inflammatory environment in which the macrophages release a significantly elevated level of inflammatory cytokines, reactive oxygen and nitrogen species, and proteolytic enzymes in an attempt to degrade the material. Interestingly, the opposite has also been observed. …show more content…
Large spherical implants (1.5-1.9 mm diameter) had stealth properties, resulting in smaller inflammatory and fibrotic responses when injected intra-peritoneally in C57BL/6 mice after a 14 day period compared to implants which were smaller (0.3-1 mm in diameter) (Veiseh et