Nonspecific and specific immune responses in a child with Down's syndrome and her sibling. A case report.

In a child with Down's syndrome (DS) and her sibling, host immune responses were evaluated under experimental gingivitis conditions. The children live in the same environment under identical conditions. In the DS child an earlier and more extensive gingival inflammation than in her sibling had been observed. Investigation of nonspecific host defense mechanisms revealed identical results in both children for the phagocytosis and intracellular killing of Candida albicans by polymorphonuclear leukocytes in crevicular washings (CR-PMNs), in blood (PB-PMNs) and blood monocytes. Furthermore, CR- and PB-PMNs were able to secrete identical amounts of hydrogen peroxide upon stimulation. The chemotactic response of PB-PMNs in the DS child was impaired, however. The results of the studies performed on parameters of specific host defense mechanisms showed low blastogenic responses to phytohemagglutinin (PHA) and pokeweed (PWM) by lymphocytes of the DS child as compared with her sibling. Also a lack of immune regulation leading to prolonged helper/inducer cell activation on a local (gingival) and circulation level and a less pronounced T-cell depression in PB were shown. Together, these differences observed in specific and nonspecific host response mechanisms may be responsible for the earlier and more extensive gingival inflammation found in the DS child.