Researchers from the United Kingdom 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. The findings, which appear in the Journal of Leukocyte Biology, may help prevent deaths from severe flu outbreaks, especially of seemingly healthy young people.

For the study, the researchers 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.

The 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 John Wherry, PhD, deputy editor of the Journal of Leukocyte Biology. “What most people don’t realize 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’ll 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