PARENT SESSION
Reproductive Immunology
427
MATERNAL IMMUNOSTIMULATION INFLUENCES EMBRYO DEVELOPMENT AND LITTER SEX RATIO IN THE NORWAY RAT.
Bacon, Sarah1, Carey, Jennifer1, Jay, Julianya1, 1
ABSTRACT- In pregnancy, maternal immune function is modulated to allow the allogeneic conceptus to survive. Uterine mucosal immunity appears particularly important to pregnancy success. In two studies we immunized virgin female Sprague-Dawley rats with either the immunostimulant Complete Freund's Adjuvant (CFA) or physiological saline (0.25ml/rat delivered subcutaneously) to assess the effect of immunostimulation on conception rate, embryo size and morphology, and litter size and sex ratio at birth. The first set of dams carried two sequential pregnancies: one pregnancy was carried to term to assess pup weight, litter size and sex ratio, and the second (postpartum-conceived) pregnancy was terminated on day 13 to assess embryo size (as measured by crown-rump length) and morphology. The second set of dams carried one pregnancy which was terminated on day 14 so that embryonic loss, morphology and size could be assessed, and placental samples could be saved for later morphological and immunohistochemical analysis. Maternal immunostimulation increased offspring size and the proportion of males born without affecting conception rate, embryonic loss, or the number of pups born. At birth the litters of CFA-treated dams had more male pups (54% male vs. 43%, p≤.01). Moreover, holding the effect of sex constant, pups born to CFA-treated dams were heavier than those born to saline-treated dams (male pups 6.83±.16 vs. 6.65±.15g, females 6.49±.18 vs. 6.24±.14g F(1,394)=4.2, p≤.05). In addition, embryos in utero were larger in CFA-treated dams on both day 13 of a postpartum-conceived pregnancy (7.02±0.55 vs. 6.89±0.67mm, p≤0.1) and day 14 of a first pregnancy (9.29±.06 vs. 9.14±.06, p≤.05). Maternal immunostimulation with CFA is correlated with increased growth of individual embryos, and also with an increased birth rate of male pups.
KEY WORDS: immunostimulation, sex ratio, embryo