UCC team discovers tummy bug clue

Researchers in Cork have made important discoveries about how the immune system works during gastro-intestinal infections.

An immune cell called a natural killer cell can attack tummy bugs directly and also intervenes to stop these inflections from spreading to other organs.

The work was done at UCC’s Alimentary Pharmabiotic Centre. It features on the cover of the current issue of Infection and Immunity.

Bacterial gastroenteritis is a major killer in developing countries but is also an increasing problem in western countries due to a rise in contaminated foods.

Scientists have long known how natural killer cells, a form of white blood cell, rush into action during viral infections and also help block tumour growth. Effectively they call in the cavalry, the immune cells and the chemical substances they produce to fight infection.

They had no known role in gastro-intestinal infections until this was revealed by the UCC research team. If harmful bacteria are detected in the gut, the killer cells migrate directly to the sites of infection and begin signalling other immune cells like B cells and T cells to join the fray. These in turn begin attacking the bacteria.

Unexpectedly, the team also found that natural killer cells have a particularly appropriate name. They make a direct attack themselves, said Dr Silvia Melgar, a senior researcher at the centre.

Dr Lindsay Hall, first author on the publication, said: “Although [natural killer] cells stimulate the immune system, which leads to the pathology associated with gastro-intestinal infection, they are also critical for reducing bacterial numbers . . . [natural killer] cells prevent the bacteria spreading to other organs, which may ultimately lead to more severe disease, for example septicaemia.” Killer cells might be the “global controller” of the immune response against stomach bugs, she adds.