Long-Term Challenges of Immunosuppression in Pediatric Patients

Clinical value of a single determination of intracellular ATP levels in stimulated CD4+ T lymphocytes in pediatric patients with stable liver transplantation

In the follow-up of transplanted patients under immunosupression, the functional assessment of CD4+ T cells activation by measuring intracellular ATP levels in vitro, using the Immuknow test give information on how immune system is functioning. Therefore, it has been reported that low levels of ATP correlate with the risk of opportunistic infection. Although limited, comprehensive results in adult recipients as well as in pediatric transplanted patients have been reported. Forty stable liver pediatric transplanted patients (mean age: 11.0 years [SD 5.65]), within at least 1 year of transplant were selected for a scheduled review, and an unique determination of Immuknow was performed. Average ATP levels were 317 ng/mL (200-400 ng/mL) which were similar to the values observed in adult population. ATP values among patients with monotherapy Cyclosporin A (CSA) or tacrolimus (TAC) were significantly higher (P = .005) than in patients with double immunosupressive therapy using either CSA/TAC + Mycophenolate Mofetil (MMF). In CSA treatment, there are significant differences (P = .0003) between monotherapy and double therapy, but in the case of TAC we did not find differences (P > .1). A single determination of levels of ATP on CD4+ lymphocytes, can provide additional information that could be used as a complementary test to guide immunosuppressive therapy in paediatric liver transplant recipients.

Selective deletion of antigen-specific CD8+ T cells by MHC class I tetramers coupled to the type I ribosome-inactivating protein saporin

CD8+ cytotoxic T lymphocytes (CTLs) are important effector cells responsible for tissue destruction in several autoimmune and allograft-related diseases. To discover if pathogenic T cells could be selectively deleted, we investigated the ability of a toxin coupled to major histocompatibility complex (MHC) class I tetramers to kill antigen-specific CD8+ T cells. H2-D(b) tetramers were assembled using streptavidin conjugated to the ribosome-inactivating protein (RIP) saporin (SAP). These tetramers inhibited ribosome activity in vitro, retained the T-cell receptor (TCR)-binding specificity of their nontoxic counterparts, and were internalized by 100% of target cells, leading to cell death in 72 hours. Cytotoxicity was dependent on the tetramer dose and avidity for the T cell. A single injection of the SAP-coupled tetramer eliminated more than 75% of cognate, but not control, T cells. This work demonstrates the therapeutic potential of cytotoxic tetramers to selectively eradicate pathogenic clonotypes while leaving overall T-cell immunity intact.