Abstract
Although both Prednisolone (PRE), a corticoid hormone, and diethylstilbestrol (DES), an estrogen-like hormone, are known to be immunosuppressive drugs, we found that mice pretreated with PRE showed enhanced resistance to Listeria infection, while mice pretreated with DES showed decreased resistance to Listeria infection. To establish useful immunoparameters of host resistance to Listeria infection, we examined the kinetics of immune cells in PRE- or DES-pretreated mice after non-lethal infection with Listeria monocytogenes. The number of CD4+CD8+, CD4+ and CD8+ T-cell subsets in the thymus and spleen and macrophage (Mac-1+ cells) in the spleen were decreased in mice pretreated with PRE, however the number of T-cell subsets in the thymus and macrophage in the spleen were remarkably increased to the level of non Listeria -infected control mice on Day 4 after Listeria infection. However, mice pretreated with DES showed a decrease in CD4+CD8+ T-cells in the thymus and a decrease in macrophages in the spleen. Furthermore, these cells continued to show decreased numbers even after Listeria infection. A remarkable increase of CD8:CD4 T-cell ratios was observed in PRE-pretreated mice but not in DES-pretreated mice. These data demonstrated that the recovery of CD4+CD8+, CD4+ and CD8+ T-cell subsets in the thymus, increased CD8:CD4 T-cell ratios in the thymus and increased macrophages in the spleen on Day 4 after the infection play important roles in increasing the resistance to Listeria infection in mice pretreated with PRE. These results also suggested that changes in immune cell kinetics could be good immunoparameters to demonstrate susceptibility to Listeria infection in mice pretreated with immunosuppressive drugs.
