Protection by group II phospholipase A(2) against Staphylococcus aureus

Group II phospholipase A(2) (PLA(2)) is an enzyme that has marked antibacte rial properties in vitro. To define the role of group II PLA(2) in the defe nse against Staphylococcus aureus, we studied host responses in transgenic mice expressing human group II PLA(2) and group II PLA(2)-deficient C57BL/6 J mice in experimental S. aureus infection; After the administration of S. aureus, the transgenic mice showed increased expression of group II PLA(2) mRNA in the liver and increased concentration of group II PLA(2) in serum, whereas the PLA(2)-defieient mice completely lacked the PLA(2) response. Ex pression of human group II PLA(2) resulted in reduced mortality and improve d the resistance of the mice by killing the bacteria as indicated by low nu mbers of live bacteria in their tissues. Human-group II PLA(2) was responsi ble for the bactericidal activity of transgenic mouse serum. These results suggest a possible role for group II PLA(2) in the innate immunity against S. aureus infection.