Chopping up a microbial tail. (Immunology).

Many disease-causing bacteria sport whip-like flagella that propel their movement. Scientists have now found that an enzyme produced by immune cells called neutrophils can chop up flagellin, the main protein in these tails.

Neutrophils are usually among the first immune cells to encounter bacteria. These cells use the enzyme neutrophil elastase to tear up the microbes' membranes. Neutrophil elastase also rips apart flagellin, report Yolanda S. Lopez-Boado of Wake Forest University School of Medicine in Winston-Salem, N.C., and her colleagues. In test-tube studies, the enzyme can destroy flagellin whether it's part of a bacterium's flagella or just free-floating in a solution.

When bacteria infect cells, they typically shed their flagella, releasing flagellin, notes Lopez-Boado. Other researchers have shown that flagellin triggers a strong inflammatory response that probably contributes to the sickness produced by a bacterial infection. Neutrophil elastase's cleavage flagellin may help the host reduce or limit that unhealthy inflammation, says Lopez-Boado.