Immunological and virological investigations in Down's syndrome.

Lymphocyte responsiveness to phytohaemagglutinin and viral antigens was studied in children with Down's syndrome and in controls. Mitogen-responsiveness in the patients was significantly reduced as compared to the control values. Using the lymphocyte transformation test, trisomic patients showed more than a twofold increase in sensitivity to herpes simplex virus as compared to controls. The same test did not show any essential difference between the two groups when adeno- and influenza viruses were used. Immunofluorescence technique, with specifically conjugated antiviral sera, permitted the detection of specific fluorescence in 30% of the patients with Down's syndrome indicating the presence of oncogenic adenovirus type 12 antigen in the circulating lymphocytes. No antibodies--or only very low titres--against adeno- and herpes simplex viruses were demonstrated in the sera of trisomic patients. Mononuclear leukocytes from these patients often showed structural alterations. The incidence of infectious herpes simplex virus and Candida albicans in the saliva of patients was higher than in the control group. It seems that Down's syndrome involves partial disturbance of both the cellular and humoral immune functions--at least with respect to certain viral antigens.