Amniotic Fluid: The First Feeding of Mucosal Immune Factors

Abstract

Amniotic fluid (AmF) provides a protective environment for the unborn fetus. A number of immunologic factors typically found in mucosal secretions, including milk, are present in AmF. These include several innate anti-microbial substances such as lysozyme, lactoferrin, transferrin, peroxidase, and interferon-α^1–5. The concentration of most of these factors increases in the AmF as the fetus matures, despite an overall decline in amniotic fluid protein concentration². Specific immunologic factors in the AmF include maternally derived IgG and low levels of IgA and IgM⁶. The IgA2 in AmF has been shown to be of fetal origin based on the allotypic marker A2m⁷. Low levels of IgA, IgM and secretory component (SC)-positive antibodies specific for Escherichia coli and poliovirus are detectable in AmF from early (14–20 wks) and late (30–40 wks) gestational samples⁸. However, the frequency of detecting these antibodies in these samples did not seem to increase with gestational age.