Salmonella enteritidis infection in rats: antigens involved in cell-mediated immunity

When rats are sub-lethally infected with S. entertidis by the intravenous route, there is a period of at least 14 days in which peritoneal exudate cells are unable to migrate from capillary tubes on to glass surfaces; thereafter they migrate as do macrophages from normal animals. The migration of peritoneal cells from rats infected 18-21 days previously is inhibited by lipopolysaccharide (LPS) prepared from homologous and heterologous strains of Salmonella. The apparent non-specificity of LPS activity in the macrophage migration inhibition test has been resolved by demonstrating that lipid A, containing less than 0.01% protein amino acids, is also capable of eliciting this test of cell-mediated immunity.