Altered cellular immune functions in patients with Down's syndrome.

Cell-associated immunocompetence was evaluated in 42 patients with Down's syndrome (DS) and compared with that of institutionalized patient control and normal control groups. B lymphocytes, as both percent of total lymphoid cells and absolute number, were markedly reduced in patients with DS. T-lymphocyte proliferative response to phytohemagglutinin mitogen also was significantly decreased. This altered response of the lymphocyte population was evident in both the presence and absence of accessory helper monocytes. Increased Fc receptor (FcR) cell activity, as measured by antibody-dependent cellular cytotoxicity was seen in both the patients with DS and the control patients. This probably resulted from common environmental factors such as exposure to infectious factors such as exposure to infectious agents. No change was found in the WBC counts, percentages of lymphocytes and monocytes, percentages of t cells and FcR cells, or in the natural killer cell activity.