Effect of increased gene dosage expression on the alpha-interferon receptors in Down's syndrome

The gene coding for the alpha, beta-interferon (alpha, beta-IFN) receptor is localized to chromosome 21. Cells from patients with Down's syndrome contain an extra chromosome 21, and thereby an expected 1.5-times increase in the number of genes located to this chromosome and in consequence a 1.5-times increase in cell surface alpha-IFN receptors. Actual measurements of these by competition binding experiments with human recombinant alpha-IFN on peripheral blood mononuclear cells (PBMC) from patients with Down's syndrome resulted in a mean of 1.69, which is in accordance to the theoretical 1.50, but slightly overestimated due to the calculation method. The increased gene dosage of the alpha-IFN receptor was quantitatively verified by Southern blot-hybridizations. Further characterization of alpha-IFN receptor binding showed insignificant differences in dissociation constants among patients and healthy individuals.