Chair of Immunology, University of Modena, Italy.
Lymphocyte subpopulations, NK and LAK activities have been studied in blood mononuclear cells from two human fetuses, the first affected by Down's syndrome, the other showing a normal karyotype. Fetuses presented similar subsets, with a scarcity of CD57+ lymphocytes but an appropriate amount of CD16+ and CD56+ cells, while negligible NK activity was detectable. After 18 h of incubation with human recombinant interleukin-2 (rIL-2), significant enhancement of the cytotoxic capability was observed. This stresses the role of IL-2 as a regulatory molecule during the development of the immune system in the human fetus.