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.

The relationship between the presence of hepatitis B surface antigen (HBsAg) and antibodies to human thyroglobulin (HTgAb) has been studied in 110 subjects with Down's syndrome (DS) from 4 months to 50 years of age and in 122 controls carefully matched for sex, age and socio-environmental conditions. The overall percentage of HBsAg carriers was 22.7 in DS and 6.6 in controls and that of HTgAb-positive subjects was 41.8 in DS and 19.7 in controls. In DS the frequency of HTgAb-positive subjects was very high, even in the youngest age groups in which the percentage of HBsAg carriers was relatively low; the latter thereafter showed a marked increase with age. A positive association between the presence of HBsAg and HTgAb was found only in the oldest age group of DS subjects. It is thus concluded that in DS the high frequency of HTgAb cannot be attributed to chronic hepatitis B virus infection. On the contrary, the presence of HTgAb might well represent an early "marker" of immunodeficiency and increased susceptibility to infection with hepatitis B virus.

Peripheral blood B lymphocytes in infancy and childhood. Acta Paediat Scand, 63:205, 1974.-In order to investigate B lymphocytes in the paediatric age, 63 normal children were examined for the presence of immunoglobulin-bearing lymphocytes in their peripheral blood. Lymphocytes were stained with a fluorescein-conjugated anti-immunoglobulin antiserum and the percentage of positive cells counted under ultraviolet light. The percentage of lymphocytes staining with fluorescein-conjugated anti-immunoglobulin antiserum has been shown to remain constant from the first days of life to adult age. It was concluded that an homeostatic mechanism maintains B cells a constant proportion of blood lymphocytes irrespective of the well known age-dependent changes in the numbers of blood lymphocytes per volume whole blood.