Derangement of non-specific immunity in Down syndrome subjects: low leukocyte chemiluminescence activity after phagocytic activation.

Metabolic activation of peripheral blood leukocytes (chemiluminescence) from 27 children with Down syndrome (DS) and 23 age and sex-matched control children after phagocytic stimulation by opsonized zymosan particles was investigated through a chemiluminescence assay. Using autologous plasma or serum as opsonizing media, phagocytic activity of circulating leukocytes was significantly decreased in DS subjects. A further decrease of phagocytic activity was found in neutrophils from DS children, when normal heterologous plasma or sera were used. On the other hand, sera or plasma from DS subjects significantly increased phagocytic activation of leukocytes from normal donors. In DS subjects opsonizing agents such as serum immunoglobulins and complement fractions were in the normal ranges of concentration. Thus, the impaired chemiluminescence of neutrophils was mainly due to a metabolic impairment at the cellular level. A decreased production of radicals derived from the oxygen metabolism in neutrophils may be an important step of immune derangement leading to the increased incidence of infectious diseases frequently associated with DS.