Immunologic parameters in Down's syndrome.

Down's syndrome children are known to have increased susceptibility to respiratory infections. Quantitative or qualitative differences in the various components of the immune system could account for increased susceptibility to infection involving the upper respiratory tract. In an effort to establish certain normal values and to determine if humoral immune abnormalities are associated with the chromosomal anomalies of Down's syndrome, immunoglobulin levels, certain complement component levels, viral antibodies, hepatitis B surface antigen and milk precipitins from a population of inpatients and outpatients were compared with those of age, sex and race matched control populations. It does not appear that the upper respiratory infections are associated with abnormally low levels of immunoglobulins or complement, with the possible exception of IgM. Both the inpatient and outpatient Down's syndrome populations had decreased levels of IgM, indicating a possible relationship with the syndrome itself. In addition, the symptomatology does not seem to be due to IgE mediated atopic sensitivity. Hepatitis B surface antigen was found only in institutionalized Down's syndrome patients, but it did not seem to be related to the other immune components studied.