Pathogenic worms have more than the immune system to contend with in mammals, with a mucus-forming protein also mounting a defence. Sugar-coated mucin proteins form a thick protective mucus layer over organs such as the gut and lungs. David Thornton and Richard Grencis at the University of Manchester, UK, and their team report that the mucin MUC5AC also directly lowers the viability of a gut-dwelling nematode worm.

MUC5AC normally occurs in the lungs, but intestinal levels shoot up in mice infected with Trichuris muris worms, a close relative of a nematode that afflicts humans. Mice lacking the Muc5ac gene had chronic worm infections, despite showing strong immune responses. In T. muris cultured with human cells, the protein limited the worms' production of the cellular energy molecule ATP — a sign of viability.

J. Exp. Med. doi:10.1084/jem.20102057 (2011)