Elevation of intracellular cyclic AMP in alloreactive CD4(+) T Cells induces alloantigen-specific tolerance that can prevent GVHD lethality in vivo.
Cyclic AMP (cAMP) is an important negative regulator of T cell activation, and an increased level of cAMP is associated with T cell hyporesponsiveness in vitro. We sought to determine whether elevating intracellular cAMP levels ex vivo in alloreactive T cells during primary mixed lymphocyte reactions (MLR) is sufficient to induce alloantigen-specific tolerance and prevent graft-versus-host disease (GVHD). Primary MLRs were treated with exogenous (8)Br-cAMP and IBMX, a compound that increases intracellular cAMP levels by inhibition of phosphodiesterases. T cell proliferation and IL-2 responsiveness in the treated primary MLR cultures were greatly reduced, and viable T cells recovered on day 8 also had impaired responses to restimulation with alloantigen compared to control-treated cells, but without an impairment to nonspecific mitogens. Labeling experiments showed that cAMP/IBMX inhibited alloreactive T cell proliferation by limiting the number of cell divisions, increasing susceptibility to apoptosis, and rendering nondeleted alloreactive T cells hyporesponsive to alloantigen restimulation. cAMP/IBMX-treated CD4(+) T cells had a markedly reduced capacity for GVHD lethality in major histocompatibility complex class II disparate recipients, but maintained the capacity to mediate other CD4(+) T cell responses in vivo. Thus, our results provide the first preclinical evidence of using cAMP-elevating pharmaceutical reagents to achieve long-term alloantigen-specific T cell tolerance that is sufficient to prevent GVHD.
O'Shaughnessy
Matthew J
MJ
University of Minnesota Cancer Center, Department of Pediatrics, Division of Bone Marrow Transplantation, Minneapolis, Minnesota 55455, USA.
Chen
Zong-Ming
ZM
Gramaglia
Irene
I
Taylor
Patricia A
PA
Panoskaltsis-Mortari
Angela
A
Vogtenhuber
Christine
C
Palmer
Ed
E
Grader-Beck
Thomas
T
Boussiotis
Vassiliki A
VA
Blazar
Bruce R
BR
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000637:transplantation*; D017690:Cell Transplantation; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism*; D006086:Graft vs Host Disease / Q000276:immunology / Q000517:prevention & control*; D007108:Immune Tolerance; D007518:Isoantibodies / Q000032:analysis / Q000276:immunology; D007959:Lymphocyte Culture Test, Mixed / Q000379:methods; D051379:Mice; D008822:Mice, Transgenic; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D016019:Survival Analysis
D007518:Isoantibodies; D010726:Phosphodiesterase Inhibitors; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine