Cell-mediated cytotoxicity in Down syndrome: impairment of allogeneic mixed lymphocyte reaction, NK and NK-like activities.

Peripheral blood mononuclear cells (PBMC) from 16 non-institutionalized patients with Down syndrome (DS) were studied with various monoclonal antibodies and analysed for natural killer (NK), and NK-like activity. Lymphocyte proliferation and cytotoxic T-lymphocyte (CTL) cytotoxicity generated in mixed lymphocyte culture (MLC) were also evaluated in 11 DS patients. Phenotypic characterization of PBMC from DS subjects confirms our previous findings of high numbers of CD8+ lymphocytes and HNK-1+, and CD16+ cells. Lymphocyte proliferation and CTL cytotoxicity generated in MLC were low or absent in most patients. NK activity was low in almost all DS patients, while NK-like cytotoxicity generated in MLC was normal in the majority and did not correlate with NK activity from unstimulated PBMC.