B-cell anergy is one mechanism utilized to expunge autoreactive immunoglobulin specificities. Anergic B-cells survive in a state of diminished antigen receptor responsiveness, and are deleted by Fas-mediated apoptosis induced by T effector cells. In normal B-cells sensitivity to Fas-directed cell death can be regulated by IL-4R and sIg signals that produce a state of Fas-resistance. The hypothesis guiding this study is that anergic B-cells may, as a result of specific immune signals, become resistant to Fas-mediated apoptosis, thereby avoiding elimination and presenting the potential for subsequent activation and autoantibody production. Elements of this hypothesis have ramifications for B-cell immunocompetence and the regulation of apoptosis in general. For this reason, and because so little is known about the means by which Fas-resistance is triggered and established, it is proposed to explore protection against Fas-directed cell death in 3 stages. 1) Evaluate the capacity of IL-4 to oppose Fas-mediated apoptosis by anti-Ig, and determine the role of other T-cell-derived lymphokines, using standard cytotoxicity assays. 2) Determine the metabolic level at which resistance to Fas-mediated apoptosis is produced by IL-4 and by anti-Ig, by examining Fas-triggered events of protein tyrosine phosphorylation, ceramide production, and protease activation, using Western blotting, identification of radiolabeled lipids, and enzymatic assays of protein digestion, and evaluate the role of Bcl-x, through tests of gene and protein expression, and evaluation of overexpressing transgenic animals. 3) Assess induction of Fas-resistance in anergic B-cells derived from double transgenic mice, and monitor autoantibodies rescued through somatic cell hybridization of B-cells from normal animals in which resistance is generated in vitro. This work should lead to a fuller understanding of the signals and mechanisms that produce B-cell resistance to Fas-mediated apoptosis, and validate or refute the hypothesis described above, which has important implications for the pathogenesis of serological autoimmunity.
