Freshly purified human blood monocytes were primed for 24 h with either LF-IC (M860+LF), or hLF, or M860, or complex between chicken ovalbumin (OVA) and OVA-specific mouse mAb M562 (OVA-IC), followed by evaluation for ability to kill leukemia line cells of Jurkat and Raji in vitro. This evidence concerns the gene LTF and leukemia.