[Evaluation of the immune system in Down's syndrome patients].

The authors carry out a study to evaluate the immunoglobulin and complement factor levels and the populations and subpopulations of mononuclear cells enumerated by monoclonal antibodies, in Down's syndrome (DS) patients. The IgG, IgA and IgM immunoglobulins were significantly increased, and presented an age-dependence. The complement factors, C3 and C4 were normal. We enumerated T lymphocyte subsets in these patients using OKT3, OKT4, OKT6, OKT8, OKIa1 and OKM1 monoclonal antibodies. The percentages of total T cells (T3 + cells) and of helper T lymphocytes (T4 + cells), were significantly decreased (DS: 49 +/- 11%; p less than 0,05) (DS: 20 +/- 7%; p less than 0,001); nevertheless in the subpopulations of suppressor/cytotoxic T lymphocytes, we found an increase (T8 + cells) (DS: 34 +/- 12%; p less than 0,01). In the remainder of the populations studied, B lymphocytes, monocytes, null-cells and common thymocytes no apparent alterations were detected. The study has shown an imbalance between populations of helper induced and cytotoxic /suppressor T lymphocytes in these patients. It appears that the unbalances in population and subpopulation studies could be due to an alteration of the Thymus. This is suggested by the increased susceptibility to polytopic infections, high risk of malignancies and high frequency of autoantibodies.