Transforming growth factor-beta-1 and interferon-beta are secreted by 3LL tumor cells and are chemotactic for lymphokine-activated killer (LAK) cells in vitro : L. Bouwens, N. Delens, P. De Baetselierì, E. Wisse, Laboratory of Cell Biology and Histology, and Laboratory of Cellular Immunology (ì), Free University Brussels (V.U.B.), Brussels, Belgium