Deletion of DOCK2, a regulator of the actin cytoskeleton in lymphocytes, suppresses cardiac allograft rejection

Allograft rejection is induced by graft tissue infiltration of alloreactive T cells that are activated mainly in secondary lymphoid organs of the host. DOCK2 plays a critical role in lymphocyte homing and immunological synapse formation by regulating the actin cytoskeleton, yet its role in the in vivo immune response remains unknown. We show here that DOCK2 deficiency enables long-term survival of cardiac allografts across a complete mismatch of the major histocompatibility complex molecules. In DOCK2-deficient mice, alloreactivity and allocytotoxicity were suppressed significantly even after in vivo priming with alloantigens, which resulted in reduced intragraft expression of effector molecules, such as interferon-γ, granzyme B, and perforin. This is mediated, at least in part, by preventing potentially alloreactive T cells from recruiting into secondary lymphoid organs. In addition, we found that DOCK2 is critical for CD28-mediated Rac activation and is required for the full activation of alloreactive T cells. Although DOCK2-deficient, alloreactive T cells were activated in vitro in the presence of exogenous interleukin-2, these T cells, when transferred adoptively, failed to infiltrate into the allografts that were transplanted into RAG1-deficient mice. Thus, DOCK2 deficiency attenuates allograft rejection by simultaneously suppressing multiple and key processes. We propose that DOCK2 could be a novel molecular target for controlling transplant rejection

Clofazimine Inhibits Human Kv1.3 Potassium Channel by Perturbing Calcium Oscillation in T Lymphocytes

The Kv1.3 potassium channel plays an essential role in effector memory T cells and has been implicated in several important autoimmune diseases including multiple sclerosis, psoriasis and type 1 diabetes. A number of potent small molecule inhibitors of Kv1.3 channel have been reported, some of which were found to be effective in various animal models of autoimmune diseases. We report herein the identification of clofazimine, a known anti-mycobacterial drug, as a novel inhibitor of human Kv1.3. Clofazimine was initially identified as an inhibitor of intracellular T cell receptor-mediated signaling leading to the transcriptional activation of human interleukin-2 gene in T cells from a screen of the Johns Hopkins Drug Library. A systematic mechanistic deconvolution revealed that clofazimine selectively blocked the Kv1.3 channel activity, perturbing the oscillation frequency of the calcium-release activated calcium channel, which in turn led to the inhibition of the calcineurin-NFAT signaling pathway. These effects of clofazimine provide the first line of experimental evidence in support of a causal relationship between Kv1.3 and calcium oscillation in human T cells. Furthermore, clofazimine was found to be effective in blocking human T cell-mediated skin graft rejection in an animal model in vivo. Together, these results suggest that clofazimine is a promising immunomodulatory drug candidate for treating a variety of autoimmune disorders

Safety and Efficacy of Reduced Prolonged-release Tacrolimus Exposure in De Novo Kidney Transplantation: A Randomized, Open-label, Pilot Study in Asia—OPTIMIZE Study

Background. A multicenter, randomized, open-label, parallel group, pilot, 52-week study in Asian countries that assessed the renal function, efficacy, and safety of reduced-exposure versus standard-exposure prolonged-release tacrolimus (PR-T) in adult kidney transplant recipients (KTRs). Methods. Posttransplantation, KTRs received PR-T from weeks 0 to 4 (initial dose, 0.2–0.3 mg/kg; target trough level, 6–10 ng/mL). At week 4, KTRs were randomized (1:1) to receive reduced-exposure PR-T (target 4–6 ng/mL, weeks 4–12; 3–5 ng/mL, weeks 12–52) or standard-exposure PR-T (target: 6–10 ng/mL, weeks 4–52). Primary end point: estimated glomerular filtration rate (eGFR) over 52 weeks. Secondary end points (week 52) included creatinine clearance, serum creatinine, graft/patient survival, biopsy-confirmed acute rejection (AR), composite of graft loss/patient death/biopsy-confirmed AR, and steroid-resistant AR. Treatment-emergent adverse events were recorded. Results. Sixty-six KTRs received PR-T (reduced-exposure, n = 32; standard-exposure, n = 34) and were analyzed. After per-protocol dose adjustment, mean ± standard deviation tacrolimus trough level was lower with reduced- versus standard-exposure PR-T (week 52, 4.5 ± 1.1 ng/mL vs 8.0 ± 2.2 ng/mL). In the reduced- versus standard-exposure group, eGFR was similar at weeks 8 to 52 (overall least-square mean difference, –2.82; 95% confidence interval, −7.91 to 2.27; P = 0.272). At week 52, there was no significant difference in creatinine clearance (P = 0.375) or serum creatinine (P = 0.547) between groups. All grafts/patients survived, no steroid-resistant AR was reported, and 4 and 3 patients had AR in reduced- and standard-exposure groups, respectively. Drug-related treatment-emergent adverse events were reported in 34.4% and 38.2% of patients, respectively. Conclusions. Reducing exposure to PR-T resulted in a clinically acceptable short-term safety profile and was generally as effective as standard tacrolimus exposure for Asian patients