EVALUATION OF THE ROLE OF EXOGENOUS PATHOGENS ON THE INCIDENCE OF EMBRYO LOSS DURING EARLY-PREGNANCY IN MICE

The mating of CBA/j female mice (H2(k)) by DBA/2j male mice (H2(d)) ty pically results in an elevated incidence of spontaneous embryo loss th us providing an ideal genetically controlled laboratory model for the study of the factors causing early embryo loss during pregnancy. There is now considerable data on the cells and factors involved in fetal r esorption but little is known about the events which activate this pro cess. While the activation of the maternal response to the fetal impla nt could have endogenous or genetic origins, a role for exogenous fact ors including microbial pathogens could also be involved. In order to investigate these possibilities, the reproductive success of CBA/j fem ale x DBA/2j male matings in a conventional animal care facility were compared with matings in a specific pathogen free (SPF) animal facilit y. All animals housed under these conditions were routinely screened b y immunoassay and culture, for the presence of a number of viral and b acterial pathogens of mice. The incidence of spontaneous embryo loss i n specific pathogen free CBA female mice mated by DBA and other male s trains was found to be virtually identical to that of CBA female mice infected with multiple viral pathogens and housed under otherwise iden tical conditions (non-SPF). However, the numbers of implantation per p regnancy was significantly greater in an SPF facility. Therefore, expo sure of mating mice to exogenous viral and bacterial pathogens did not appear to alter the overall incidence of spontaneous embryo resorptio n. It was concluded that the immunomodulatory effects of infection by common murine pathogens neither augmented nor reduced post-implantatio n embryo losses.