Huhtinen HT, Grönroos JO, Grönroos JM, Uksila J, Gelb MH, Nevalainen TJ, Laine VJO. Antibacterial effects of human group IIA and group XIIA phospholipase A2 against Helicobacter pylori in vitro. APMIS 2006;114:127–30. Group IIA phospholipase A2 (PLA2-IIA) is an enzyme which has important roles in inflammation and infection. Recently, a novel human secretory PLA2 called group XIIA PLA2 (PLA2-XIIA) has been identified. Both PLA2-IIA and PLA2-XIIA are bactericidal against Gram-positive bacteria like many other secretory PLA2s. However, PLA2-XIIA is the only known PLA2 displaying significant bactericidal activity against the Gram-negative bacterium Escherichia coli. We examined the antibacterial properties of recombinant human PLA2-IIA and PLA2-XIIA against Helicobacter pylori, a Gram-negative bacterium, in vitro. PLA2-IIA was not bactericidal against H. pylori, whereas PLA2-XIIA effectively killed H. pylori at a concentration of 50 μg/ml but was not bactericidal at concentrations of 0.5 μg/ml and 5 μg/ml.