First, NK cells purified from four healthy donors were cultivated for 18 h with either PRO or BRY and, in parallel, with IL-15 or without stimuli (nt), then incubated in a 4-h lysis assay at various effector-to-target (E:T) ratio with K562 cells, a tumor cell line that serves as established target of NK cytotoxicity. The gene discussed is IL15; the disease is neoplasm.