PROBLEM: Previous studies have demonstrated a requirement for RANTES (regulated 
on activated normal T-cell expressed, and secreted) at immune privileged sites; 
we have investigated the role of RANTES in the induction of maternal-fetal 
tolerance.
METHOD OF STUDY: Endometrial and peripheral T lymphocytes were obtained from 
women with recurrent pregnancy losses (RPLs) and fertile women. RANTES 
modulation by progesterone or paternal alloantigens was measured by 
enzyme-linked immunosorbent assay or flow cytometry analysis.
RESULTS: Progesterone significantly increased intracellular RANTES expression in 
CD4+ and CD8+ endometrial T cells. Moreover, alloreactive lymphocytes from RPL 
patients produced lower RANTES levels when compared with those from fertile 
women. At the local level, treatment with recombinant RANTES induced a decrease 
in CCR5 and CXCR4 messenger RNA that correlated with an increase in T-bet 
expression. RPL patients and normally fertile women express RANTES similarly, 
but differ in their patterns of RANTES receptor expression.
CONCLUSION: RANTES may be implicated in the local induction of a Th1-type 
response necessary for successful implantation. Altered response to RANTES 
stimulation among some RPL patients may be responsible for poor pregnancy 
outcomes.