The aim of this proposal is to attempt to detect and characterize EBV associated transformation and tumor antigens on cells infected with EBV. These cells will include B cells of normal individuals infected in vitro (in vitro lines), lymphoblastoid cell line from infectious mononucleosis patients (IM) and from Burkitt lymphoma biopsies (BL), and epithelial cells from nasopharyngeal carcinoma (NPC). Monoclonal antibodies will be prepared against these antigens by immunizing mice with plasma membranes depleted of major histocompatability complex antigens. Resulting hybridomas will be screened for specific reactivity with each cell type using a two step radioimmunoassay. EBV negative lymphoblastoid cell lines and autologous mitogen induced blasts will be used as a negative control. The expression of these antigens on infected cells in vivo will be tested using peripheral lymphocytes of patients with acute IM, fatal IM, uncontrolled EBV associated B cell proliferative diseases and biopsy material from BL and NPC. We will test the antibodies for their ability to block the antigens recognized by already characterized T cell responses: in vivo, non-HLA restricted cytotoxicity, and in vitro, HLA restricted cyto-toxicity and interferon associated factor release to suppressing transformation. The detection of antigens in vivo already defined in vitro by T cell responses will implicate those responses in the mechanism for recovery from disease. We will further test the in vivo occurrence of these T cell responses by cloning activated peripheral T cells from IM patients and searching for clones which will perform the in vitro defined responses. Monoclonal antibodies which react only with IM/in vitro lines will be used for selection of antigen negative sublines and the tumorigenicity before and after selection will be compared with standard BL lines to test the hypothesis that BL arises through selection by immune surveillance of a single antigen negative clone. These studies should yield information about the mechanism which brings the lymphoproliferation associated with EBV infection under control in normal individuals, or fails in certain special circumstances (e.g., BL). Lastly, the antibodies produced could prove useful in routine screening for EBV in other proliferative diseases.