FETAL ORIGIN OF AMNIOTIC-FLUID POLYMORPHONUCLEAR LEUKOCYTES

OBJECTIVE: Although polymorphonuclear leukocytes are the inflammatory cells most frequently recovered from the amniotic cavity in cases of s uspected intrauterine infection, the source of these cells has not bee n definitively determined. We took advantage of the gender difference between the mother and her male fetus, and we report four cases in whi ch amniotic fluid polymorphonuclear leukocytes were identified as feta l by fluorescence in situ hybridization with probes specific for X and Y chromosomes. Fetal membranes were intact at the time amniotic fluid was obtained in all cases. STUDY DESIGN: Amniotic fluid was obtained from women with male fetuses in premature labor with clinical or labor atory evidence of infection. Cytospin preparations of amniotic fluid s amples with polymorphonuclear leukocytes were prepared and sequentiall y stained with fluorescent reagents. To determine which cells were pol ymorphonuclear leukocytes, all replicate samples were stained with the fluorescent nuclear stain 4'-6-diamidino-2-phenyl-indole. This allowe d definition of the characteristic multilobed polymorphonuclear leukoc ytes nuclear morphologic features. The sample was then probed with a r hodamine-labeled probe specific for the X chromosome and a fluorescein -labeled probe specific for the Y chromosome to assess whether the pol ymorphonuclear leukocytes were male or female. RESULTS: Ninety percent to 99% of polymorphonuclear leukocytes identified by normal multiple lobed nuclear morphologic study on 4'-6-diamidino-2-phenyl-indole stai ning had an X and Y chromosome and were therefore fetal cells. CONCLUS ION: These data demonstrate a fetal response during intraamniotic infe ction. Further investigation of the roles for maternal and fetal polym orphonuclear leukocytes in chorioamnionitis may provide valuable infor mation about the critical interaction of the two immune responses in t his setting.