[Diminished zinc plasma concentrations and alterations in the number of lymphocyte subpopulations in Down's syndrome patients].

Alterations of plasma levels of zinc and in the immune system in Down's syndrome (DS) have been reported. These alterations have been associated with a high rate of infectious diseases, which represent the main cause of mortality in affected individuals. The objectives of this study were to determine plasma zinc levels and to evaluate the immune system in DS patients. Peripheral blood samples were obtained from 43 DS patients examined at the Unidad de Genética Médica, Universidad del Zulia in Maracaibo, Venezuela. Their mean age (+/- SD) was 2.3 +/- 2.0 years. As control group, 40 healthy children were studied (mean +/- SD 2.3 +/- 2.0 years). Karyotypes by a standard technique, the determination of plasma levels of zinc by atomic absorption spectrophotometry and the evaluation of the immune system by flow cytometry were carried out in the study groups. All DS patients had free trisomy 21. Significantly disminished zinc plasma levels, helper T lymphocyte (CD4) percentage, helper/cytotoxic (CD4/CD8) ratio and B-cells (CD19) were found in DS patients by matching with control group. An increase in CD8 was also found. No significative difference in the lymphocyte subpopulations between DS patients with disminished plasma levels of zinc and DS patients with normal zinc were found. These findings suggest that zinc deficiency is not the sole etiology involved in the disorders of immune system seen in DS patients. Other factors, such as thymic alterations and molecular abnormalities due to gene overexpression of loci located on chromosome 21 could be involved. Although, zinc supplementation is recommended in these patients with zinc deficiency, further studies with a double-blind, placebo versus zinc design are needed to evaluate the potentially beneficial effects of zinc treatment in DS patients.