The human tumor necrosis factor-alpha (TNF-alpha) gene encodes a cytokine whose activities have been implicated in many immunopathological processes including the hemorrhagic necrosis of tumor cells, inhibition of viral infection and as a key mediator in septic shock. Originally identified as a monocyte factor, our studies and those of others have demonstrated that B and T lymphocytes produce TNF-alpha when stimulated by a variety of inducers. These observations are of significance in light of the role that TNF-alpha plays in the activation and differentiation of lymphocytes. In addition, lymphocyte-derived TNF- alpha induces HIV-1 expression from latently infected T- and monocytic cell lines and appears to play an important role in T-cell mediated lethal shock syndrome triggered by superantigen. The overall goal of the proposed research is to investigate TNF-alpha gene expression in T- and B-cells activated by physiological immune stimulation. Our initial studies have demonstrated that TNF-alpha mRNA is rapidly and highly induced in T-and B-cells activated by antibodies to the T-cell receptor (TcR) and immunoglobulin (Ig), respectively. Moreover, we have found in both cell types that this induction is independent of protein synthesis and is blocked by the immunosuppressant cyclosporine A (CsA). We have identified a TNF-alpha promoter element and a binding factor that is important in the mediation of TcR activation and the CsA-sensitivity of the gene.
The specific aims of the proposed research include the further characterization of this TNF-alpha cis- acting promoter element, kappa3, and the trans-acting factor that binds to it. Our preliminary results indicate that this factor is a novel CsA- sensitive factor that is induced by activation through the TcR/CD3 complex. Its isolation and characterization may therefore provide unique insights into immunosuppressant action and perhaps into the synthesis of future immunosuppressive agents. Moreover, these studies have the potential of elucidating early lymphocyte activation events common to both T- and B-cells and the transcription factors that are involved in initial lymphocyte activation and differentiation. Our studies of the anti-Ig induction and CsA-sensitivity of TNF-alpha gene expression in B-cells is particularly interesting in light of the polyclonal B-cell stimulation associated with many infectious diseases. We have observed that anti-Ig antibody induction of the Epstein-Barr virus lytic cycle is also blocked by CsA in B-cells. These studies establish CsA as a useful probe in dissecting transcriptional pathways in activated B-cells. The study of human TNF-alpha gene expression in activated lymphocytes will provide important insights into lymphocyte activation, immunosuppressant action, and inducible gene expression. Investigation of these findings may uncover possible immune therapeutic approaches for infection by lymphotropic viruses and other pathogens. Characterization of this model system should also increase our understanding of the immunopathological role of TNF-alpha in many disease states.
