Altered T-cell receptor+CD28-mediated signaling and blocked cell cycle progression in interleukin 10 and transforming growth factor-beta-treated alloreactive T cells that do not induce graft-versus-host disease

The induction of anergy in T cells, although widely accepted as critical fo r the maintenance of tolerance, is still poorly understood at the molecular level, Recent evidence demonstrates that in addition to blockade of costim ulation using monoclonal antibodies (mAbs) directed against cell surface de terminants, treatment of mixed lymphocyte reaction (MLR) cultures with inte rleukin 10 (IL-10) and transforming growth factor-beta (TGF-beta) results i n induction of tolerance, rendering alloreactive murine CD4(+) T cells inca pable of inducing graft-versus-host disease (GVHD) after in vivo transfer t o histoincompatible recipients. The present study, using these cells prior to adoptive transfer, determined that IL-10 + TGF-beta -tolerant CD4(+) T c ells exhibit an altered pattern of T-cell receptor (TCR) + CD28-mediated si gnaling and are incapable of progressing out of the G1 phase of the cell cy cle during stimulation with HLA class II disparate antigen-presenting cells . TGF beta + IL-10-tolerant cells were incapable of phosphorylating TCR-xi, or activating ZAP-70, Ras, and MAPK, similarly to T-cell tolerized by bloc kade of B7/CD28 and CD40/CD40L pathways. Moreover, these cells were incapab le of clonal expansion due to defective synthesis of cyclin D3 and cyclin A , and defective activation of cyclin-dependent kinase (cdk)4, cdk6, and cdk 2. These cells also exhibited defective down-regulation of p27(kip1) cdk in hibitor and lack of cyclin D2-cdk4 activation, Rb hyperphosphorylation, and progression to the S phase of the cell cycle, These data link anergy-speci fic proximal biochemical alterations and the downstream nuclear pathways th at control T-cell expansion and provide a biochemical profile of IL-10 + TG F-beta -tolerant alloreactive T cells that do not induce GVHD when transfer red into MHC class II disparate recipients in vivo. (C) 2001 by The America n Society of Hematology.