CHANGES IN IMMUNOLOGICAL PROPERTIES OF NEUTROPHIL ALKALINE-PHOSPHATASE IN TRISOMY-21 PREGNANCIES

Immunoreactivity, cytochemical, immunocytochemical characteristics and subcellular distribution of neutrophil alkaline phosphatase (NAP) wer e investigated in blood and/or smear samples from 18 women aged 23-46 years (mean 32.5 years) with trisomy 21 fetuses (17-21 weeks) and 28 w omen aged 20-42 years (mean 31 years) with normal fetuses (17-22 weeks ). Immunochemical NAP investigations were carried out in 8 pathologica l and 8 normal pregnancies; cytochemical and immunocytochemical proced ures were carried out in 18 pregnant women with trisomy 21 fetuses and 28 controls. NAP from women with trisomy 21 fetuses is characterized by: (1) a significant decrease in reactivity with anti-liver-type alka line phosphatase (AP) and anti-NAP antisera; (2) low or very slight re activity with antiplacental or anti-intestinal antibodies; (3) marked dispersion of NAP lead citrate reaction products or anti-NAP antibody colloidal gold-labelling in neutrophil cytoplasms, as detected by elec tron microscopy. This subcellular AP distribution (extramembranous) is different from that of normal NAP sites associated with plasma membra ne, nuclear membrane and secretory vesicles. The NAP immunochemical an d cytochemical characteristics suggest that neutrophils of a woman wit h a trisomy 21 fetus contain two AP isoenzymes: the liver/bone type an d an atypical AP.