Pla2g5, encoding group V phospholipase A2, is a lipid-generating enzyme. It liberates membrane-bound lipids in a tissue and cell-specific manner. It is involved in lipid metabolism-related pathways and is crucial for macrophage effector functions in pulmonary inflammation, M2 macrophage development, and has a role in regulating transglutaminase activity in human IL-4-activated M2 macrophages [2,3].

Genetic models, especially KO/CKO mouse models, have been instrumental in revealing its functions. In Pla2g5-deficient mice, poly:IC-induced lung inflammation was diminished, including reduced inflammatory macrophage proliferation. Adding linoleic acid (LA) partially restored the inflammation, indicating Pla2g5 contributes to lung inflammation by regulating macrophage proliferation and LA/Ffar1-mediated lung cell recruitment [1]. Also, in mice lacking Pla2g5, there was reduced lung ILC2 activation and eosinophilia following repetitive Alternaria Alternata inhalation, with reduced FFAs (including LA) in lung and BM-macrophages. Exogenous LA potentiated IL-33-induced lung eosinophilia and ILC2 expansion in wild-type but not Pla2g5-null mice, suggesting Pla2g5 contributes to type-2 immunity through regulating IL-33 induction and FFA-driven ILC2 activation [3].

In conclusion, Pla2g5 is essential for macrophage-related functions in inflammation and type-2 immunity. The study of Pla2g5 KO/CKO mouse models has enhanced our understanding of its role in lung-related diseases and immune-mediated processes, providing insights into potential therapeutic targets for these conditions.