The shape of things to ingest

Macrophages are concerned more with the shape than size of their victims when it comes to phagocytosis. The new findings, reported by Julie Champion and Samir Mitragotri (University of California, Santa Barbara, CA), may inspire innovations in drug delivery strategies.

For this first systematic examination of the effect of shape on phagocytosis, Champion and Mitragotri synthesized their own IgG-coated polystyrene particles, using natural macrophage targets as inspirations (spherical and rod-shaped particles mimic bacteria, flat discs resemble red blood cells, etc). Macrophages ingested each and every shape, but only if the target was initially encountered from the correct side—the one that required the most gradual expansion of the membrane as it englufed the particle.

“There is a right and a wrong shape from the macrophage's perspective,” says Mitragotri....