The goals of this grant are to continue the characterization of a novel monocyte activating factor (MAF) produced by the T-cell hybridoma FtF3 (ATCC HB 9713) developed in this laboratory. The specific aims are: 1. Sequence both MAF proteins 2. Prepare synthetic peptides to confirm sequence/activity relationship, function, and for production of monoclonal antibodies. 3. Production of monoclonal antibodies. 4. Make cDNA and/or oligonucleotide probes, and isolated the gene. Identification of these factors are important in the understanding of the immunology of lymphocyte/monocyte interactions, and may be of potential clinical value in augmenting the immune response against tumors and microorganisms.