Fetal Leukocytes in the Maternal Circulation After Delivery

The presence of fetal cells in the maternal circulation after delivery was investigated by examining interphase cells for fluorescent Y-bodies after staining with quinacrine mustard. Mothers were excluded if their own autosomos had regions of brilliant fluorescence that simulated Y-bodies. In a study of 24 primiparas, the sex of whose children was unknown to the observer, the method was found to be reliable: 34 of the 240,000 cells examined showed a presumptive Y-body, and only one of these cells was from a woman who had delivered a female infant. Results of the study of 46 primiparas who had given birth to male children were: 14 (30%) had fetal lymphocytes and granulocytes, 17 (37%) had fetal lymphocytes only, 3 (7%) had fetal granulocytes only, and 12 (26%) had no Y-body-containing cells. Unequivocal evidence that presumptive interphase Y-bodies represented XY cells, was obtained by screening phytohomagglutinin-stimulated cultures of lymphocytes from three mothers. In each, one XY mitosis was found. Cell counts at intervals after delivery showed that fetal granulocytes disappeared within 1 week, whereas fetal lymphocytes persisted for at least 1 year. Cytotoxic antibodies directed against paternally derived fetal HL-A antigens were produced by 10 of 85 primiparas tested (22%). Tests for both fetal cells and HL-A antibodies at delivery were performed in 44 mothers. There was a clear-cut correlation between the presence of antibodies and the absence or paucity of fetal cells. No correlation was noted between the occurrence of cytotoxic antibodies and ABO incompatibility between mother and fetus.