Richard Lamb and his post doctoral fellow Virginie Mieulet, in the Faculty of Medicine & Dentistry, may be able to explain why proper nutrition（营养） is so vital in fighting infection. They have discovered an amino acid（氨基酸） , called arginine（精氨酸） , is required to let the body know that it's being attacked by an infection.

It is still early in their work but this discovery could have implications for the millions of people in third world countries that do not get enough food and consequently become ill with infection.

It may also be the mechanism involved in chronic（慢性的，长期的） inflammation, like arthritis（关节炎） because if you have too much arginine it may cause the body to be in a constant state of thinking it is being attacked.

In a healthy person, macrophages（巨噬细胞） are the first cells to arrive at the site of infection. They eat the infected cells and present a molecule that is recognized by the immune system on the surface of the infected cell which attracts more immune fighting cells to the area. According to Lamb it is known that arginine is essential for the function of macrophages but until now no one realized that arginine has a much bigger role.

In their most recent work, Lamb and Mieulet presented arginine to a laboratory model. These models were better able to fight infection even if they were malnourished（营养不良的） .

"This is a major work," said Lamb. "If this holds true in humans it shows that one aspect of nutrition that is critical is the level of amino acids."