Blocking the Common γ-Chain of Cytokine Receptors Induces T Cell Apoptosis and Long-Term Islet Allograft Survival

The cytoplasmic localized Janus tyrosine kinase 3 (Jak3) is activated by multiple cytokines, including IL-2, IL-4, and IL-7, through engagement of the IL-2R common γ-chain. Genetic inactivation of Jak3 is manifested as SCID in humans and mice. These findings have suggested that Jak3 represents a pharmacological target to control certain lymphoid-derived diseases. Using the rat T cell line Nb2-11c, we document that tyrphostin AG-490 blocked in vitro IL-2-induced cell proliferation (IC50 ∼20 μM), Jak3 autophosphorylation, and activation of its key substrates, Stat5a and Stat5b, as measured by tyrosine/serine phosphorylation analysis and DNA-binding experiments. To test the notion that inhibition of Jak3 provides immunosuppressive potential, a 7-day course of i.v. therapy with 5–20 mg/kg AG-490 was used to inhibit rejection of heterotopically transplanted Lewis (RT1l) heart allografts in ACI (RT1a) recipients. In this study, we report that AG-490 significantly prolonged allograft survival, but also acted synergistically when used in combination with the signal 1 inhibitor cyclosporin A, but not the signal 3 inhibitor, rapamycin. Finally, AG-490 treatment reduced graft infiltration of mononuclear cells and Stat5a/b DNA binding of ex vivo IL-2-stimulated graft infiltrating of mononuclear cells, but failed to affect IL2Rα expression, as judged by RNase protection assays. Thus, inhibition of Jak3 prolongs allograft survival and also potentiates the immunosuppressive effects of cyclosporin A, but not rapamycin.

mentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Concomitant Inhibition of Janus Kinase 3 and Calcineurin-Dependent Signaling Pathways Synergistically Prolongs the Survival of Rat Heart Allografts

Behbod

Erwin-Cohen

Wang

et al. 2001

“…Similarly, injection of sIL-15R␣ delays the development of collagen-induced arthritis and suppresses the accompanying collagen-specific T cell response (14). The recent availability of mice genetically deficient in IL-15 will further clarify the role of IL-15 in these and other immunopathologies (32) T cell growth factors play an essential role in allograft rejection, as highlighted by the recent demonstration that blockade of the common ␥-chain, a key signaling component shared by IL-2, IL-4, IL-7, IL-9, and IL-15 receptors, prevents rejection in a murine islet transplant model (33). Further studies are now needed to define more clearly the contributions of individual growth factors in the graft rejection process, and in the case of IL-15 these will be facilitated by the availability of sIL-15R␣.…”

Section: Discussionmentioning

confidence: 99%

Selective Blockade of IL-15 by Soluble IL-15 Receptor α-Chain Enhances Cardiac Allograft Survival

Smith

Bolton

Ruchatz

et al. 2000

IL-15 is a T cell growth factor that shares many functional similarities with IL-2 and has recently been shown to be present in tissue and organ allografts, leading to speculation that IL-15 may contribute to graft rejection. Here, we report on the in vivo use of an IL-15 antagonist, a soluble fragment of the murine IL-15R α-chain, to investigate the contribution of IL-15 to the rejection of fully vascularized cardiac allografts in a mouse experimental model. Administration of soluble fragment of the murine IL-15R α-chain (sIL-15Rα) to CBA/Ca (H-2k) recipients for 10 days completely prevented rejection of minor histocompatibility complex-mismatched B10.BR (H-2k) heart grafts (median survival time (MST) of >100 days vs MST of 10 days for control recipients) and led to a state of donor-specific immunologic tolerance. Treatment of CBA/Ca recipients with sIL-15Rα alone had only a modest effect on the survival of fully MHC-mismatched BALB/c (H-2d) heart grafts. However, administration of sIL-15Rα together with a single dose of a nondepleting anti-CD4 mAb (YTS 177.9) delayed mononuclear cell infiltration of the grafts and markedly prolonged graft survival (MST of 60 days vs MST of 20 days for treatment with anti-CD4 alone). Prolonged graft survival was accompanied in vitro by reduced proliferation and IFN-γ production by spleen cells, whereas CTL and alloantibody levels were similar to those in animals given anti-CD4 mAb alone. These findings demonstrate that IL-15 plays an important role in the rejection of a vascularized organ allograft and that antagonists to IL-15 may be of therapeutic value in preventing allograft rejection.

“…Hence, other effector mechanisms that are insensitive to ␥c signals can still mediate CD28/CD154 blockade-resistant rejection in diabetic NOD hosts. Blocking the ␥c alone can inhibit T cell activation and induce long term islet allograft survival in conventional mice (17), but such an effect was not observed in the diabetic NOD recipients (Fig. 3), further suggesting that the mechanisms mediating islet allograft rejection in conventional mice are different from those in diabetic NOD mice.…”

Section: Discussionmentioning

confidence: 80%

“…The hybridoma cells were grown in serum-free UltraCulture medium (BioWhittaker, Walkersville, MD), and the mAb was purified from the culture supernatant using protein G columns. Rat anti-mouse ␥c mAbs (4G3/3E12) were produced and used as previously reported (16,17). Control rat IgG and hamster IgG were purchased from Sigma-Aldrich (St. Louis, MO).…”

Section: Reagentsmentioning

confidence: 99%

Islet Allograft Rejection in Nonobese Diabetic Mice Involves the Common γ-Chain and CD28/CD154-Dependent and -Independent Mechanisms

Demirci

Strom

2003

Self Cite

Once nonobese diabetic (NOD) mice become diabetic, they are highly resistant to islet transplantation. The precise mechanism of such resistance remains largely unknown. In the present study we tested the hypothesis that islet allograft survival in the diabetic NOD mouse is determined by the interplay of diverse islet-specific T cell subsets whose activation is regulated by CD28/CD154 costimulatory signals and the common γ-chain (γc; a shared signaling element by receptors for IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21). We found that common γc blockade is remarkably effective in blocking the onset and the ongoing autoimmune diabetes, whereas CD28/CD154 blockade has no effect in suppressing the ongoing diabetes. However, CD28/CD154 blockade completely blocks the alloimmune-mediated islet rejection. Also, a subset of memory-like T cells in the NOD mice is resistant to CD28/CD154 blockade, but is sensitive to the common γc blockade. Nonetheless, neither common γc blockade nor CD28/CD154 blockade can prevent islet allograft rejection in diabetic NOD mice. Treatment of diabetic NOD recipients with CD28/CD154 blockade plus γc blockade markedly prolongs islet allograft survival compared with the controls. However, allograft tolerance is not achieved, and all CTLA-4Ig-, anti-CD154-, and anti-γc-treated diabetic NOD mice eventually rejected the islet allografts. We concluded that the effector mechanisms in diabetic NOD hosts are inherently complex, and rejection in this model involves CD28/CD154/γc-dependent and -independent mechanisms.