PROBLEM: Several studies indicate that RANTES (regulated on activation, normal T 
cell expressed and secreted) is able to downregulate T-cell responses which 
suggest it might be relevant for fetal tolerance induction. However, the role of 
RANTES in pregnancy had not been established. Here we investigate RANTES 
regulation during early pregnancy and potential failures leading to losses of 
pregnancies.
METHOD OF STUDY: RANTES and progesterone levels were determined in sera and 
feto-placental units from high resorption rate CBA/JxDBA/2 pregnant females and 
compared with CBA/JxBALB/c normal pregnant mice. RANTES in vitro modulation was 
also studied in nulliparous, primiparous and multiparous CBA/J and BALB/c cells 
in response to paternal alloantigen and progesterone stimulation.
RESULTS: Nulliparous CBA/J females were quantitatively deficient in RANTES sera 
levels, whereas pregnancies with male BALB/c or DBA/2 increased its production. 
However, feto-placental units from CBA/J females are high producers of 
progesterone and RANTES.
CONCLUSION: These data suggest that the beneficial effect of RANTES on 
feto-maternal interface requires an optimal concentration range and might be 
modulated by progesterone, hence exacerbated placental expression could be 
associated with high resorption rate.