PRF1 and lymphoma: IL‐12/15/18‐preactivated NK cells upregulated Perforin and FasL in vitro, thus potentially enhancing cytotoxicity, but they did not vigorously degranulate in response to any of the targets tested, including YAC‐1 and A20 lymphomas, LPS‐matured allogeneic BMDCs, ConA‐activated allogeneic T cells, or naïve or alloantigen‐activated syngeneic T cells.