RELATIONSHIP BETWEEN DECIDUAL LEUKOCYTE INFILTRATION AND SPONTANEOUS-ABORTION IN A MURINE MODEL OF EARLY FETAL RESORPTION

The relationship between the early cellular response to embryo implant ation and subsequent embryo survival was explored. Immunohistochemistr y using the anti-CD11b antibody (Mac-1) was used to localize and quant ify maternal inflammatory cells present at the fetoplacental interface . CD11b is expressed mostly on macrophages, but is also present on nat ural killer (NK) cells, neutrophils, and B cells, The occurrence of CD 11b-positive cells at the fetoplacental interface was quantified in CB A/J females mated by DBA/2 males (20-30% embryo loss) and CBA/J female s mated by BALB/c males (5-10% embryo loss) in order to investigate th e relationship between infiltration by these types of cells and subseq uent embryo loss. CD11b-positive cells were found to infiltrate decidu a of each embryo starting at Day 6 of gestation. Their numbers sharply increased on Days 7 and 8, to a plateau on Days 8 to 10, well before any damage to the embryo is macroscopically visible on Days 10 to 12 o f gestation. The resorption-prone mating of CBA/J female by DBA/2 male showed a significantly elevated number of CD11b-positive cells in 26% of the embryos on the eighth day of gestation compared to CBA/J femal e by BALB/c male matings which were taken as the reference mating. Mor eover, experimental conditions modulating fetal survival in CBA/J moth ers such as poly (I:C) treatment of DBA/2-mated females (lower surviva l) or mating with BALB/c males (higher survival than with the mating w ith DBA/2 males), were found to be associated with high or low numbers of CD I Ib-positive cells at the fetoplacental interface. Furthermore , injection of anti-CD11b into pregnant mice at Day 6 of gestation sig nificantly reduced the subsequent incidence of resorption in the resor ption prone CBA/J X DBA/2 mating. These results suggest that CD11b-pos itive cells are associated with the etiology of spontaneous abortion i n this system. (C) 1994 Academic Press, Inc.