Interleukin (IL)-15 enhances antibody-dependent cellular cytotoxicity and natural killer activity in neonatal cells

Interleukin (IL)-15 is a novel cytokine that is very similar to IL-2 in receptor specificity and biological activities. We compared the ability of IL-15 and IL-12 to enhance the cytotoxicity of neonatal (cord blood) and adult mononuclear cells (MNC) in both natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) assays. Incubation with IL-15 (10 ng/ml) or IL-12 (1 ng/ml) for 18 h enhanced the NK activity (using K562 target cells) of both cord and adult MNC, increasing cord cell cytotoxicity threefold. Similar enhancement was seen in ADCC assays using erythrocyte targets and NK-resistant CEM cells coated with HIV gp-120 antigen. Incubation of cord cells with IL-15 or IL-12 for 1 week increased both NK and ADCC, although the combination produced less of an effect than either cytokine alone. IL-15 also increased the percentage of CD16+/CD56+ cells after 1 week incubation. This enhancement of NK and ADCC activities and the number of NK cells by IL-15 suggests it may be clinically useful in treating immunodeficient patients.