Host defense proteins in vernix caseosa and amniotic fluid.

OBJECTIVE: This study was undertaken to define the spectrum, activity, and spatial distribution of antimicrobial peptides in vernix caseosa and amniotic fluid in the absence of clinical chorioamnionitis. STUDY DESIGN: Characterization of innate immune proteins in vernix and amniotic fluid obtained from pregnancies with gestational ages greater than 37 weeks by Western analysis, immunohistochemistry, and antimicrobial growth inhibition assay. RESULTS: Lysozyme, lactoferrin, human neutrophil peptides 1-3, and secretory leukocyte protease inhibitor were identified by Western analysis in vernix suspensions (n = 25) and amniotic fluid samples (n = 10). Three other important antimicrobial proteins, human beta defensin-2, lactoperoxidase, and LL-37 were not detected. Amniotic fluid and soluble extracts of vernix exhibited muramidase (lysozyme) activity, and there was selective efficacy in inhibiting growth of common perinatal pathogens. Antimicrobial peptides were concentrated in discrete, organized, acellular "granules" embedded in the vernix lipid matrix. CONCLUSION: In the absence of chorioamnionitis, vernix and amniotic fluid contain an organized pool of antimicrobial peptides with a defined spectrum of bioactivity against common bacterial and fungal pathogens.