Age, Environment, and Lymphocyte Immunization Influence the Spontaneous Resorption Rate in the CBA/J × DBA/2J Mouse Model

PROBLEM: This study was designed to examine the influence of age, environment, and lymphocyte immunotherapy on fetal resorption rates in the CBA/J × DJA/2J mouse model. METHODS: After weaning, CBA/J female mice were randomly allocated to two different environments: room A was a conventional housing facility, and room B was a specific pathogen‐free room. They were further divided into two groups in each room according to age (> three months and ≤ three months), and mated with CBA/J, DBA/2J, or BALB/c males. The fetal resorption rates were observed. The immunization study was conducted using CBA/J females greater than three months old in room B. Preimmunization with various preparations and dosages of lymphoctyes was performed 1 wk before mating with DBA/2J males, and fetal resorption rates were measured to investigate the effect of immunotherapy. RESULTS: In room A, the fetal resorption rates (9.4 to 11.8%) were not significantly different among the various mating combinations using CBA/J females greater or less than three months of age. In room B, CBA/J females older than three months and mated with DBA/2J males had a higher rate of fetal resorption than those younger than three months (28.9 versus 14.2%) and had higher rate of fetal resorption than those housed and mated in room A (28.9 versus 10.9%). This fetal resorption rate was also higher than those seen with other mating combinations. Preimmunization with male BALB/c splenic lymphocytes (optimal dose 1 × 10 7 cells) was effective in decreasing fetal resorption rate (7.9%), whereas administration of normal saline, or immunization with male CBA/J or DBA/2J lymphocytes was not (20.7 to 27.0%). CONCLUSION: Age and environment influence the spontaneous resorption rate in the CBA/J × DBA/2J mouse model. The high fetal resorption rate of older CBA/J females mated with DBA/2J males in a pathogen‐free environment can be reduced by immunization with BALB/c splenic lymphocytes. These results suggested that a variety of mechanisms might initiate early pregnancy failure and that immunological modulation during implantation might be a nonspecific factor.