| abstract |
To provide in situ hybridization assays in which the sex of a fetus, genetic characteristics or abnormalities, infectious agents or identification of other chemical, biochemical or genetic properties are detected by nucleic acid hybridization of fetal cells, such fetal cells, which circulate in maternal blood, are enriched, detected and interrogated. The techniques are capable of detecting a single genetic abnormality in a single cell, involving as few as approximately 75 base pairs, by visual microscopic examination. Genetic abnormalities may include deletions, additions, amplifications, translocations or rearrangements. Multiple abnormalities may also be detected simultaneously, and they may be visually distinguished by color. Cells may be obtained from amniocentesis, chorionic villi sampling, or in vitro fertilization embryos or products of conception, but are preferably from maternal peripheral blood. Fetal cells such as lymphocytes, erythrocytes or trophoblasts may be enriched from maternal blood. Erythrocytes may be enriched by removing maternal white blood cells with an immobilized antibody to a cell surface antigen, e.g. CD45. Fetal cells may be enriched by density gradient centrifugation. Fetal cells are desirably distinguished from maternal cells by staining, e.g. with a labeled antibody to cytokeratin or to fetal hemoglobin of for fetal hemoglobin by hematoxylin/eosin, or by in situ hybridization to detect one or more fetal mRNAs, e.g., fetal hemoglobin or fetoprotein. Kits are provided for the disclosed procedures. |