ICAM-1 (CD54) expression on T lymphocytes and natural killer cells from umbilical cord blood: Regulation with interleukin-12 and interleukin-15

We investigated the effect of two immunoregulatory cytokines, interleukin (IL)-12 and IL-15, alone or in combination, on intercellular adhesion molecule I (ICAM-1, CD54) expression on mononuclear cells (MNC) obtained from umbilical cord blood (CB) and adult peripheral blood (APB). We established that (1) ICAM-1 expression was deficient on freshly isolated CB T and natural killer (NK) cells compared with that on adult cells; (2) ICAM-1 expression on T cells (CD3⁺/CD54⁺), but not on NK cells (CD16⁺/CD54⁺), was spontaneously upregulated after 7 days' culture in RPMI with 10% fetal calf serum (FCS) in the absence of cytokines, for CB and APB MNC alike; (3) removal of 10% FCS from the medium did not affect the spontaneous CD3⁺/CD54⁺ upregulation on APB MNC; (3) CB NK cells responded more readily to IL-12 and IL-15 than did APB NK cells in terms of ICAM-1 expression, while ICAM-1 expression on APB T cells, but not on CB T cells, could be enhanced with IL-12 plus IL-15; (4) the combination of IL-12 and IL-15 downregulated ICAM-1 expression on both CB and APB NK cells. Thus, we demonstrated the different patterns of ICAM-1 regulation by CB MNC and APB MNC in response to IL-12 and/or IL-15 and the differential effect of cytokines on the regulation of adhesion molecules on neonatal NK and T cells.