White blood cells set the pace of wound repair
After more than 50 experiments in mice, scientists have mapped out how a set of white blood cells (lymphocytes) set the pace of recovery after serious lung injury.
In acute lung injury (ALI), inflammation in the lungs makes breathing difficult. This results in a lack of oxygen to the body. Previous research indicated that lymphocytes play a role in lung inflammation, so the researchers bred mice genetically modified to be lymphocyte deficient.
They then exposed normal mice and the lymphocyte deficient mice to a gas containing bacteria known to cause injury to the lungs. They compared the death rates between the two groups of mice and saw a higher death rate in the mice without lymphocytes. They concluded that lymphocytes are key to recovery after lung injury.
To determine which type of lymphocytes were responsible for this response, the team then injected mice with different types and combinations of lymphocytes. They found that the levels of a particular subset of lymphocytes known as Tregs were directly proportional to the levels of lung inflammation.
To test the ability of Tregs as a potential therapy, they doubled the exposure of the bacterial toxin to the mice. This increased the death rate to half in untreated mice. However, when mice were administered Tregs after exposure to the toxin, the death rate fell to just one tenth, with many showing signs of recovery after just six days. Studies on lung tissue extracts from two people with ALI also showed that after 48 hours, Tregs were at 10 times the normal level. This discovery opens up the possibility of speeding up, or supplementing the levels of Tregs, so the next step is to identify the process by which Tregs cause the mouse immune response to repair the tissue.