Figure 6. Effect of the EGTA/MgCl2 combination, anti-Salmonella IgG, and mannose-binding lectin on killing of NTS by control adult serum and child serum lacking specific antibody to Salmonella.
In vitro killing of S. Typhimurium isolate D23580 by serum was determined at 45, 90, and 180 minutes (initial concentration, 106 salmonellae/ml). (A) Killing of Salmonella by control adult serum (squares) and inhibition of killing by addition of 10 mM EGTA and MgCl2 (triangles). (B) Absence of killing of Salmonella by child serum lacking Salmonella-specific antibody (squares). Addition of 0.2 g/l exogenous IgG containing anti-Salmonella antibody enabled killing of Salmonella in child serum lacking Salmonella-specific antibody (triangles), but not in heat-inactivated serum (circles). (C) Inability of child serum lacking Salmonella-specific antibody to kill Salmonella (squares) was unaffected by addition of 5 μg/ml exogenous mannose-binding lectin (triangles). Data are mean ± 1 SD of 3 experiments.