IMMUNOGLOBULIN-G SUBCLASSES IN OLDER PERSONS WITH DOWN-SYNDROME

IgG subclasses were measured in sera from 33 persons with Down syndrom e (DS) (mean age 55 +/- 7 years) and 33 age- and sex-matched control i ndividuals using a mouse monoclonal antibody based sandwich enzyme lin ked immunosorbent assay. Significantly higher levels of IgG1 and IgG3 and lower levels of IgG2 and IgG4 subclasses were found in the DS grou p compared to the control individuals. The higher levels of IgG, and I gG, subclasses found in DS persons were consistent with those seen in patients with autoimmune diseases and chronic viral infections; the lo wer levels of IgG2 and IgG4 subclasses were consistent with those seen in patients with recurrent infections. Our findings are similar to th ose reported in children with DS. We speculate that the subclass level s may have little or no relationship to the development of brain lesio ns typical of Alzheimer disease in older persons with DS. There were n o significant differences between the levels of IgG subclasses of pers ons with DS showing signs of dementia of the Alzheimer type compared t o those without such manifestations.