Neutrophils take the easy way out

To migrate out of blood vessels into inflamed tissues, blood cells must cross both the vessel endothelium and basement membrane (BM). According to Wang and colleagues (page 1519), protein-sparse exit sites in the BM pave the way for this cellular escape.

The signals required for blood cells to adhere to sites of vessel inflammation and to squeeze through endothelial cell (EC) junctions are well defined. But it is unclear how the cells then traverse the tough, underlying network of BM proteins. Migrating cells, such as neutrophils, produce proteases that can cleave BM proteins, which may help the cells drill through the BM.

But Wang and colleagues favor a less destructive model, as drilling holes in the BM could inflict irreversible vessel damage. They now show that steady-state expression of certain (but not all)...