EBV specific cytotoxic T cells (CTL) have been shown to be effective in preventing and treating EBV induced lymphoproliferative disease in stem cell transplant patients, and adoptive immunotherapy with HLA identical donor lymphocytes has also been applied to an organ transplant patient with this disorder, resulting in complete remission of the disease. The present proposal is to administer HLA identical or haplo-identical EBV CTL to organ transplant patients with EBV-LPD and to monitor these patients for clinical and radiographic response. Patient peripheral blood specimens will be examined post infusion using minisatellite PCR analysis for the presence of donor lymphocyte DNA. Donor CTL will be immunophenotyped at intervals post-infusion. EBV specific cytotoxic T lymphocyte precursor frequencies will be obtained at intervals post infusion. The nature of the cytotoxic response will be evaluated from patient calls as well as donor EBV CTL with regard to MHC restriction, the degree of inhibition of cytotoxicity with monoclonal antibodies directed against Class I, HLA-DR, and CD-3, and the role of B-7/CD28 co-stimulation in the expansion of donor CTL and in patient CTL responses to EBV. The T cell receptor (TCR) VB phenotype will be characterized on infused T cells as well as on patient lymphocytes to correlate disease status, in vitro CTL response, and TCR repertoire. EBV CTL will also be cultivated from EBV sero-negative donors and cord blood mononuclear cells to examine the immune response to EBV BLCL in individuals without a prior infection with this virus. As part of this goal, patient lymphocytes will also be cultured with autologous EBV BLCL to expand populations of EBV reactive CTL. Cloned as well a polyclonal EBV CTL obtained from patients will be expanded with submitogenic doses of CD3 and CD28, with the goal of expanding sufficient number of these cells that could be potentially used for therapeutic infusion. Semi-quantitative EBV PCR will be performed on all organ transplant patients for one year post transplant at monthly intervals in order to determine a correlation between then presence of EBV-LPD and elevated levels of EBV DNA from peripheral blood lymphocytes. This test may be useful in early diagnosis of EBV-LPD in these patients, at a time when their lymphoproliferations are more likely to be controlled by decreased immunosuppression.