Direct lysis of bovine epithelial cells (line MDBK) by NK cells. NKp46⁺ cells from peripheral blood of neonates less than 8 days old, and calves (6 months old), were sorted and cultured in the presence of rb-IL2 (100 U/mL) or rh-IL15 (10 ng/mL) during 7–10 days and used in a flow cytometry cytotoxicity assay. (A) Direct lysis of MDBK target cells by NK cells from neonates (open symbols) or calves (filled symbols). Data represent means ± SEM (n = 3 for cells cultured with IL-2; n = 5 for cells cultured with IL-15). Statistical analysis is based on the one-way Wilcoxon test: p < 0.05 for IL-15 expanded NK cells. (B) Sorted NKp46⁺ cells cultured for 6 days in the presence of rhIL-15 were labelled with anti-perforin mAb (solid lines) or with isotype control mAb (shaded area). Data shown are from one animal representative of three.