Proteome analysis of vernix caseosa.

Vernix caseosa (vernix) is a white creamy substance covering the skin of the fetus during the last trimester of pregnancy. The function of vernix has long been debated but no consensus has been reached. We here report a proteome analysis of vernix using two-dimensional gel electrophoresis, matrix-assisted laser desorption/ionization mass spectrometry and liquid chromatography coupled to tandem mass spectrometry. We have identified 41 proteins, of which 25 are novel to vernix. Notably, 39% of the identified vernix proteins are components of innate immunity, and 29% have direct antimicrobial properties. These results form a substantial contribution to the knowledge of vernix composition and demonstrate that antimicrobial protection of the fetus and the newborn child is a major and important function of vernix.