title: Cutting edge: distinct TCR- and CD28-derived signals regulate CD95L, Bcl-xL, and the survival of primary T cells.
abstract: TCR-driven clonal expansion of T cells is limited by activation-induced cell death through CD95/CD95L interactions. This cell-contact dependent mechanism is attenuated by costimulation through CD28. Here, we show that primary rat lymph node T cells activated by "superagonistic" CD28-specific mAb, which do not require TCR-engagement for full T cell activation, do not up-regulate CD95L. CD28 superagonist activated T cells are highly resistant to artificial CD95 cross-linking, and display a marked up-regulation of the survival factor Bcl-x(L). Consistently, NF-kappaB factors, known to promote Bcl-x(L) transcription, are strongly activated by superagonistic CD28 mAb stimulation. In contrast, a weaker induction of NFAT, which positively regulates the CD95L gene, in CD28 activated cells as compared with TCR- or TCR/CD28-stimulated cells was observed. Thus, by recruiting the mitogenic activity of CD28 in the absence of TCR engagement, the anti-apoptotic signals provided by costimulation are revealed without interfering proapoptotic effects induced by TCR stimulation.
authors.affiliation: Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kerstan
authors.forename: Thomas
authors.initials: T
authors.lastname: Hünig
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000276:immunology*; D018106:CD28 Antigens / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D002470:Cell Survival / Q000276:immunology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000276:immunology; D053222:Fas Ligand Protein; D008024:Ligands; D008213:Lymphocyte Activation / Q000276:immunology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology*; D014157:Transcription Factors / Q000378:metabolism; D015854:Up-Regulation / Q000276:immunology; D051020:bcl-X Protein; D019014:fas Receptor / Q000378:metabolism / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; C494813:Bcl2l1 protein, rat; D018106:CD28 Antigens; D004268:DNA-Binding Proteins; D053222:Fas Ligand Protein; C505662:Faslg protein, rat; D008024:Ligands; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011948:Receptors, Antigen, T-Cell; D014157:Transcription Factors; D051020:bcl-X Protein; D019014:fas Receptor