Intercellular communication by lymphocyte hormones, or lymphokines, is instrumental in the regulation of immune responses that maintain host defense against infection, prevent autoreactivity, and provide surveillance against neoplasia. The investigation of lymphokines will increase our understanding of disordered immune regulation and provide new therapeutic agents for many human diseases. The investigation of each lymphokine requires a comprehensive approach including purification to homogeneity, chemical characterization, assessment of biological functions, the production of monospecific antibodies, and gene cloning. Our laboratory has purified to homogeneity a neutrophil migration inhibition factor, (NIF-T), which is a neutrophil activating factor produced by helper T-lymphocytes. This accomplishment establishes the feasibility of achieving the remaining goals. 1. To establish in vitro assay models of neutrophil-mediated cytotoxicity that are both antibody dependent and independent. 2. To determine the effect of NIF-T, a neutrophil activating factor, on neutrophil-mediated tumor cell cytotoxicity. 3. To clone the gene for NIF-T to provide abundant quantities of NIF-T for laboratory and clinical studies.