Detection and enumeration of colonic mucosal cells in amniotic fluid using a colon epithelial‐specific monoclonal antibody

Since its introduction, prenatal diagnosis of chromosomal and metabolic disorder by mid‐trimester amniocentesis has relied upon the use of a mixture of fetal cells obtained from amniotic fluid. Little knowledge has been gained in the sorting of these cells for diagnosis of tissue‐specific disorders. In an attempt to determine the contribution of fetal colonic mucosal cells to the overall amniocyte population, we used the colonic epithelial‐specific monoclonal antibody (MC‐Ab) 7E₁₂H₁₂, IgM isotype. Specimens of the small intestine, colon, buccal mucosa, kidney, urinary bladder, and umbilical cord were obtained from electively aborted normal fetuses of 12–28 weeks' gestation. All of these specimens were examined with 7E₁₂H₁₂ by the immunoperoxidase technique. The MC‐Ab reacted with the colonic epithelial cells but not with any of the other tissues. In addition, 40 amniotic fluid samples obtained from women between 16 and 18 weeks of gestation, who underwent amniocentesis because of advanced maternal age, were tested using a fluorescent activated cell sorter. Among the amniotic fluid specimens examined, 18·4 ± 10·3 percent cells reacted with 7E₁₂H₁₂. Double immunofluorescence studies revealed that all Mc‐Ab‐stained cells contained secretory component, confirming that they were epithelial in origin. All fetuses whose amniotic fluid was analysed had normal karyotypes and amniotic fluid alpha‐fetoprctein levels that were also normal. This study demonstrates that cell‐specific Mc‐Ab can be used to detect colon cells in the amniotic fluid and that colon cells contribute significant numbers in the mixture of amniotic fluid cells. This technique could be helpful in the prenatal diagnosis of disorders in which the flow of amniotic fluid through the fetal intestine is impaired, such as cystic fibrosis, imperforate anus, Hirschsprung aganglionic megacolon, and intestinal atresia.