Chromatin structure in Down's syndrome.

In the chromatin of patients with Down's syndrome, changes are shown to occur in a short-term lymphocyte culture of the human peripheral blood. Some of them are induced by the patient's blood serum and are reversible when this is replaced by normal serum. A 100-fold dilution of the blood serum taken in subjects with Down's syndrome does not produce any changes in the structure of the lymphocyte chromatin of the patients. A similar procedure with the blood serum of healthy donors resulted in a drastic activation of their lymphocyte chromatin. These experiments, and investigations on the effect produced by the blood serum on the model desoxyribonucleoprotein systems, support the suggestion that the changed state of the chromatin in subjects with Down's syndrome is caused by a complex set of components contained in the blood serum, whose degree of dissociation deviates from the normal.