Neutrophil alkaline phosphatase (NAP) from 12 mothers of normal children
was investigated and the results compared to those of 7 mothers with trisomy 21 offsprings,
in an attempt to determine a parental molecular change in this chromosomal abnormality.
The biochemical properties of the enzyme were analyzed by the procedures of isoenzyme
characterization, i.e. enzyme assays, thermostability, inhibition patterns and slab gel electrophoresis.
Immunological properties were determined on 5 samples from normal mothers and
on the same sample number of mothers with affected children. In these latter NAP showed
characteristics that were to some extent different from the ones of normal controls. The
following changes were observed: highly significant loading of membrane and nucleus pellets
in NAP activity, poor effect of inhibitors on thermostable component and immunodepletion
measured by a significant decrease of the normal affinity for antiliver and antiplacental
alkaline phosphatase antisera. These findings are discussed in the light of our knowledge of
alkaline phosphatase isoenzymes.