Difference in activity properties and subcellular distribution of neutrophil alkaline phosphatase between normal individuals and patients with trisomy 21

Abstract

Biochemical, cytochemical characteristics and electron microscopy subcellular distribution of neutrophil alkaline phosphatase (NAP) were analysed in blood and/or smear samples from 39 trisomy 21 patients (Down's syndrome) aged 11.5-18 years (mean 15.5 years) and 55 normal subjects aged 12-20.5 years (mean 17 years). All patients were karyotyped. NAP cytochemical procedures were carried out on all subjects; biochemical NAP determinations were made in 10 patients and 20 controls; ultrastructural electron microscopy of AP was performed in three patients and four normal subjects. Neutrophil alkaline phosphatase from patients with trisomy 21 displayed the following changes: (1) a significant increase of enzyme activity, (2) a high thermal lability of enzyme. Electron microscope morphology exhibited large deposits of NAP reaction product associated with the plasma membrane and intracellular main organelles, like phosphasomes. The NAP biochemical and cytochemical characteristics suggest that trisomy 21 neutrophils contain a non-specific AP isoenzyme, closely related to the early placental form.

Heat stable and urea resistant alkaline phosphatase in maternal neutrophils from normal and Down syndrome pregnancies

“…PAP is synthesized in the syncytiotrophoblast and reaches the maternal circulation early in the first trimester (Okamoto et al, 1990). An association between elevated activity of neutrophil PAP and trisomy 21 was reported in affected individuals (Lennox et al, 1962;Tangheroni et al, 1971;Grozdea et al, 1991), as well as in mothers with presently ongoing or previous Down syndrome pregnancies (Grozdea et al, 1983;Vergnes et al, 1988;Grozdea et al, 1988;Brisson-Lougarre et al, 1991;Denier et al, 1996). An increase in PAP activity was also described in maternal serum in the second trimester of affected pregnancies (Ind et al, 1994;Denier et al, 1996).…”

“…Sera were collected from 7 ml blood and stored at 80 C. Polymorphonuclear cells were isolated from 7 ml heparinized venous blood (Grozdea et al, 1991) and the average neutrophil yield was 91 per cent 3·8 per cent (Coulter Ltd, England). Cells were disrupted by three exposures to sonication (190W, Heat-System Inc., Model-XL2020), 30 seconds each with 30 second breaks in between.…”

“…The sonicates were centrifuged at 16 900 g for 40 minutes at 4 C and the pellets were resonicated in Krebs-Ringer buffer (Sigma) containing 0·1 per cent triton for 30 seconds. AP was extracted with cold buthanol for 30-45 minutes at 4 C and the supernatant was dialysed overnight against 0·1 M tris buffer pH 8 containing 1 mM of ZnCl 2 and MgCl 2 (Trepanier et al, 1976;Benham et al, 1978Benham et al, , 1981Grozdea et al, 1991). Samples were used either immediately or divided into aliquots and stored at 80 C. AP activity was assayed with the fluorogenic substrate 4-methyl-umbelliferyl phosphate (Sigma) according to Grozdea et al (1984) and with the chromogenic substrate p-nitrophenyl phosphate (Sigma) according to Gainer and Stinton (1982).…”

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“…or is the presence of PLAP in neutrophils responsible for a predisposition of trisomy 21 pregnancy ? As neutrophils of trisomy 21 patients contain only NSAP [ 45 , 46 ], we can reject the second hypothesis. Then the presence of PLAP in neutrophils is not genetically determined and seems to be a consequence of the presence of a trisomy 21 fetus.…”

About the Presence of a Circulating Anti-Alkaline Phosphatase Antibody in a Trisomy 21 Patient’s Serum

“…Neutrophil alkaline phosphatase (AP) from patients with trisomy 21 (Down's syn drome) displayed a significant increase in enzyme activity and a marked thermolabil ity of the enzyme when compared to normal controls [1], This study was conducted on a group of 11 teenagers, carriers of a free tri somy 21 diagnosed by karyotyping of blood lymphocytes. In the series examined, we found a 17-year-old boy with a different bio chemical neutrophil AP pattern.…”