You’ll already know something about macrophage cells if you’ve seen The Blob – a 1950s sci-fi thriller about an amoeba-like organism that terrorises earthlings as it devours all in its path. The word macrophage literally means “the large thing that devours”. These large scavenger cells (pictured), up to a hair-width across, are the bulldozers of our immune system. They clear the body of detritus, including dead cells, bacteria, and the millions of airborne pollen, carbon and grit particles that we ingest on a busy road. In laboratory experiments, researchers fed macrophages with spherical silica beads, taking snapshots as the cells attacked them. Ten minutes passed from the moment the cells’ chemical receptors pinpointed their target (left) and engulfed them (right). When they swapped spherical beads with slightly aspherical ones, the process took twice as long, suggesting that pathogens with irregular shapes could slow-down the engulfment process, potentially increasing their virulence.
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