Liver helps body fight infection

The liver responds to increase defenses in the blood that prevent localized infections from spreading throughout the body, Boston University researchers said. Study leader Joseph P. Mizgerd, a professor, and Lee J. Quinton, an assistant professor, at BU School of Medicine, said the acute-phase response is an innate immune response in which dozens of blood proteins change in concentration due to physiological stresses such as infection, inflammation and injury. The change in concentrations of proteins such as C-reactive protein can be measured in the blood and can indicate risk or progression of disease, the researchers said. "While the acute-phase response was discovered in 1930, the mechanism and meaning behind the changes in certain blood protein concentrations are not well understood," Mizgerd, who also is the director of the Pulmonary Center at BUSM, said in a statement. The researchers mutated two transcription factor genes, STAT3 and RelA, in liver cells. The cells, called hepatocytes, generate the blood proteins that change during an acute-phase response, Mizgerd said. The mutations had no measurable effect prior to infection. In response to pneumonia, which normally triggers the acute-phase response, the mutations prevented such changes in the blood proteins. Thus, the acute-phase response was specifically inhibited, Mizgerd said. "For the first time, we have shown the acute-phase response that occurs as a result of a lung infection triggers the liver to mount bloodstream defenses, preventing the infection from spreading throughout the body," Mizgerd said. The findings are scheduled to be published in the May edition of the Journal of Clinical Investigation.