Interferon-γ Detection in Cultures of Newborn Cells Exposed toListeria monocytogenes

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Abstract
Clearance of Listeria monocytogenes in experimental models of infection has underscored the importance of interferon-gamma (IFN-gamma) in host resistance to intracellular pathogens. Because L. monocytogenes infections are more severe in newborns than adults, we compared IFN-gamma accumulation in the supernatants of mononuclear cells infected in vitro from newborns with those from adults. Supernatants were assayed for IFN-gamma using an enzyme-linked immunosorbent assay. Uninfected newborn and adult mononuclear cells had less than 50 pg/ml of IFN-gamma at all times tested. IFN-gamma levels in supernatants from infected adult mononuclear cells at 24 h of culture (1.15 x 10(3) +/- 0.92 pg/ml) were greater than supernatants from infected newborn mononuclear cells (0.19 x 10(3) +/- 0.33 pg/ml). IFN-gamma concentrations in newborn cell cultures plateaued on day 3 of culture (1.6 x 10(3) +/- 1.1 pg/ml) and were not significantly less than concentrations from adult cells. However, adult cell IFN-gamma was further increased by day 5 (18.7 x 10(3) +/- 21.8 pg/ml). Because IFN-gamma plays a critical role in the host defense against L. monocytogenes, this delay in the release of IFN-gamma may be a factor in the increased susceptibility and severity of infection in the neonate.