Proapoptotic activated T-cells in the blood of children with Down's syndrome: relationship with dietary antigens and intestinal alterations.

Immune defects, thyroid abnormalities, infections and coeliac disease are often associated with Down's syndrome (DS). However, the basis of the immune defects is still unclear in DS. In the present study, we show that peripheral CD4 T-cells were decreased in children with DS, while mean values of cytotoxic CD8 T-cells were comparable with those from healthy children. Circulating activated (CD3/HLA-DR positive) T-cells were increased and a large proportion of purified T-cells from DS were also positive for APO-I/FAS (CD95) antigen. To further explore the functional status of circulating activated T-cells, enriched CD3 lymphocytes were cultured for 3 h and were tested for positivity to annexin-V (ANX-V) and propidium iodide. T-cells with the early apoptotic phenotype were increased in cell cultures from DS children. Plasma levels of inteleukin-6 (IL-6) were higher in DS children than in healthy children. The incidence of coeliac disease was also increased in this group of children. Most DS children showed increased levels of circulating IgG or IgA specific for gliadin, and their plasma IL-6 levels correlated with those of antigliadin IgG. The number of CD4 circulating cells was very low in DS children with coeliac disease, was low in those with serum antigliadin antibodies and was normal in DS without antigliadin antibodies. An overload of dietary antigens and impaired nutrient absorption secondary to altered functioning of the gastrointestinal mucosa might interfere with normal immune responses by inducing programmed cell death in CD4 T-cells.