Derangements of immunoglobulin levels, phytohemagglutinin responsiveness and T and B cell markers in Down's syndrome at different ages.

Immunologic studies were performed in 83 patients with Down's Syndrome (DS) in ages ranging from a few months to 30 years and 76 karyotypically normal age-matched controls. The results show that both thymus-dependent and independent functions were impaired in DS with a characteristic age sequence. Serum immunoglobulin levels were normal in children with DS less then 5 years old; after 6 years of age a definite hyperglobulinemia of the IgG and IgA type was observed. A slight decrease in IgM was observed between 16 and 25 years of age. In subjects with DS lymphocyte phytohemagglutinin responsiveness was in the normal range during the first decade but it decreased thereafter progressively; the percentage and absolute number of peripheral blood lymphocytes forming "spontaneous rosettes" with sheep erythrocytes were abnormally low at all ages including infancy; the number of circulating lymphocytes with a high density of surface immunoglobulins was always in the normal range.