Disturbance of redistribution of surface membrane receptors on peripheral mononuclear cells of patients with Down's syndrome and of aged individuals.

Redistribution of surface membrane immunoglobulins (SmIg) and concanavalin A (Con-A) receptor sites were studied in the peripheral mononuclear cells of institutionalized patients with Down's syndrome (DS), non-DS patients from the same institution, normal hospital staff members, and a group of healthy-appearing older volunteers averaging over 85 years of age. Two ligands were chosen: fluorescein-labeled polyvalant goat anti-human immunoglobulin for T-depleted mononuclear cells, and fluoresceinated Con-A for unfractionated peripheral mononuclear cells. The percentage of cells showing capping of SmIg and Con-A receptor sites was significantly lower in aged persons and in DS patients than in non-DS patients and normal staff members. Such a disturbance of mobility of cell membrane receptors in aged persons indicates the existence of alterations in surface membrane and associated structures of peripheral mononuclear (lymphoid) cells with aging in humans. The finding of a lower degree of capping in DS than in controls of similar age supports the supposition that DS shows features of accelerated aging.