Cause of Lung Injury

Specifically, the researchers found that immune cells called, "natural killer T cells," may reduce the overwhelming numbers of another type of immune cell, called "inflammatory monocytes," which when present in large numbers, lead to lung injury at the end stage of severe flu infection.

"We hope this study will ultimately benefit individuals — especially the young — who succumb to a severe form of flu infection," said Doctor Ling-Pei Ho of the Oxford University. "The study highlights a key immune process that occurs in severe flu infection, and provides a platform for a new approach and further research in this area."

To make their discovery, scientists infected three groups of mice with H1N1 flu virus. The first group included normal mice. The second group was devoid of natural killer T cells, and the third was given a treatment that specifically activated natural killer T cells. Researchers observed the outcome of flu infection and found that the mice without natural killer T cells did worst, and those with activated killer T cells did best. Mice that lacked natural killer T cells had increased amounts of monocytes in the lungs, and severe lung injury similar to those seen in Spanish flu and lethal swine flu. Using highly-sensitive fluorescent antibody technology, this study was one of the first to document the sequential changes in innate immune response in the lungs during severe flu infection. These findings essentially provide a "road map" of the chronological changes in the lungs during severe flu infection.

"Despite affecting practically everyone, the flu may be one of the most underestimated viruses in terms of its devastating potential," said Doctor John Wherry. "As the H5N1 research shows, it is quite possible for the virus to mutate or be bioengineered into a form that could wipe most of us out. What most people do not realise is that the severe illness from these flu strains is caused by both the virus and an overaggressive or inappropriate immune response. Research like this, however, offers hope that we will be able to find more universal ways improve the effectiveness of immunity and combat the severe strains of the flu."; Source: Federation of American Societies for Experimental Biology