Interferon-γ Detection in Cultures of Newborn Cells Exposed to Listeria monocytogenes

Abstract

Clearance of Listeria monocytogenes in experimental models of infection has underscored the importance of interferon-γ (IFN-γ) in host resistance to intracellular pathogens. Because L. monocytogenes infections are more severe in newborns than adults, we compared IFN-γ accumulation in the supernatants of mononuclear cells infected in vitro from newborns with those from adults. Supernatants were assayed for IFN-γ using an enzyme-linked immunosorbent assay. Uninfected newborn and adult mononuclear cells had less than 50 pg/ml of IFN-γ at all times tested. IFN-γ levels in supernatants from infected adult mononuclear cells at 24 h of culture (1.15 x 10³ ± 0.92 pg/ml) were greater than supernatants from infected newborn mononuclear cells (0.19 x 10³ ± 0.33 pg/ml). IFN-γ concentrations in newborn cell cultures plateaued on day 3 of culture (1.6 x 1O³ ± 1.1 pg/ml) and were not significantly less than concentrations from adult cells. However, adult cell IFN-γ was further increased by day 5 (18.7 X 10³ ± 21.8 pg/ml). Because IFN-γ plays a critical role in the host defense against L. monocytogenes, this delay in the release of IFN-γ may be a factor in the increased susceptibility and severity of infection in the neonate.