Listeria monocytogenes infection in pregnant mice: abnormalities in the function of non-adherent accessory light density dendritic cells.

Pregnant A/J mice were found to be more susceptible to the lethal effect of Listeria monocytogenes bacteria than virgin females. However, during the first four days of post-infection there was no difference in the elimination of Listeria from the spleens of pregnant and virgin mice. This suggests that the increase in the susceptibility of pregnant mice to pathogenic activity of L. monocytogenes was related to the diminution in Listeria-specific cellular reactions. Indeed, we found that non-adherent light density dendritic cells (DCs) from pregnant mice showed a marked reduction in the ability to form clusters with L. monocytogenes immune T lymphocytes and it is known that cell cluster formation between antigen presenting cells (APC) and responding T cells is required for antigen recognition as well as for cell proliferation. DCs from pregnant mice also demonstrated the decrease and an instability in the expression of H-2 class II molecules which play a crucial role in the recognition of exogenous antigens. The abnormalities demonstrated in the function of the light density dendritic cells from the spleens of pregnant mice could compromise cellular reactions to L. monocytogenes bacteria possibly resulting in increased susceptibility of pregnant mice to experimental listeriosis.