Analysis of blood cell populations, plasma zinc and natural killer cell activity in young children with Down's syndrome.

Down's syndrome (DS) is associated with respiratory infections, lymphoblastic leukemia and a mortality rate that is elevated particularly during the first 5 years of life. Unfortunately, most studies on immune function in DS have been performed on adults or older children, the results of which may be not relevant to a primary immune defect in DS since maturation of the immune system and compensatory mechanisms may mask to a certain degree primary immune defects which are associated with this syndrome. In the present study, several immune and hematologic parameters were studied in DS children under 6 years of age and in age-matched controls. The children with DS exhibited a reduced number of lymphocytes while the total number of white blood cells was normal. In addition, the children with DS had reduced numbers of circulating OKT4+ cells and a significantly depressed ratio of OKT4+ to OKT8+ cells, but their overall proportion of T-cells was normal. Normal NK activity was observed and cells from DS children were no more sensitive to the augmenting effects of alpha interferon than cells from control children. Hematocrit levels were slightly elevated in the DS group while plasma zinc levels appeared to be normal in this group.