RESUMO
Abstract: Down's syndrome [DS] is the most common chromosomal abnormality in humans. It is characterized by precocious immunologic aging that results, among other things, in alterations of T lymphocyte subsets and natural killer cells. DS subjects have an increased prevalence of autoimmune disorders. The most common autoimmune disease in DS is related to the thyroid gland
Aim of work: investigate some indicators of immune response, such as white blood cells, lymphocytes, CD3+, CD4+, CD8+, CD56+ peripheral blood mononuclear cells and to study thyroid function and the presence of thyroid autoantibodies in DS children and to compare them with the same items in healthy children
Subjects and Methods: This study was carried on twenty six children; 15 children with DS, their age ranged from 13 to 63 months [32.8+/-15.6] and 11 healthy children matching in age and sex with DS children. Five ml venous blood samples were collected aseptically from each child. Evaluation of total leucocytic count, lymphocytes, CD3+, CD4+, CD8+ and CD56+ cells was carried for each subject. TSH and FT4 were measured by chemiluminesence and thyroid autoantibodies [antithyroglobulin and anti TSH receptor antibodies] were measured by radioimmunoassay
Results: Total leucocytic count, Lymphocyte count, CD3+ and CD4+ cells were lower in DS children [total leucocytic count was 5773.3 cells /mm3 +/- 1862.2, lymphocyte count was 2235.3+/-598.9, CD3+ cells were 1775.3+/-397.6, and CD4+ cells were 762.0+/-299.5] than healthy controls [total leucocytic count was 7909.1+/-1465.9, lymphocyte count was 3160.0+/-723.6, CD3+ cells were 2253.1+/-637.9, CD4+ cells were 1390.4+/-380.5] with statistical significant difference. CD8+ and CD56+ cells were higher in DS children [CD8+ cells were 980.5+/-286.3 and CD56+ cells were 394.3+/- 104.0] than healthy controls [CD8+ cells were 742.9+/-171.7 and CD56+ cells were 176.6+/-53.9] with statistical significant difference. CD4/CD8 ratio was reversed in DS children [0.79+/- 0.28]. Seven patients [46.7%] with DS were hypothyroid according to thyroid profile tests; while none of the control group revealed any abnormality in thyroid function. Thyroid autoantibodies were detected in 3 [20%] of DS children [2 hypothyroid and 1 euthyroid patients] and in none of the control group. In conclusion, a complex impairment of T-lymphocytes and natural killer cell production takes place in DS children. The sum of these alterations is likely the cellular basis of the defective immune responses and of the increased susceptibility to infectious diseases occurring in DS subjects. Thyroid dysfunction is common in DS children and thyroid autoantibodies are not uncommon in preschool DS children