De Mello's Single Incision for Combined Liver-kidney Transplantation, Keeping the Kidney Retroperitoneal: A Case Report.

The combined liver-kidney transplantation (cLKT) is the procedure of choice for patients with end-stage liver and kidney disease. In cLKT we can usually accommodate the grafts in two different ways, varying the kidney placement. The retroperitoneal kidney implant has some advantages, such as the easy access or avoiding vascular complications. We propose a new single incision, not yet reported, maintaining an extraperitoneal kidney, with excellent surgical field for cLKT and possible reduction of the impact of wound complications.

Renal transplantation in human immunodeficiency virus-infected recipients: a case-control study from the Brazilian experience.

BACKGROUND: Highly active antiretroviral therapy has turned human immunodeficiency virus (HIV)-infected patients with end-stage renal disease into suitable candidates for renal transplantation. We present the Brazilian experience with kidney transplantation in HIV-infected recipients observed in a multicenter study. METHODS: HIV-infected kidney transplant recipients and matched controls were evaluated for the incidence of delayed graft function (DGF), acute rejection (AR), infections, graft function, and survival of patients and renal grafts. RESULTS: Fifty-three HIV-infected recipients and 106 controls were enrolled. Baseline characteristics were similar, but a higher frequency of pre-transplant positivity for hepatitis C virus and cytomegalovirus infections was found in the HIV group. Immunosuppressive regimens did not differ, but a trend was observed toward lower use of anti-thymocyte globulin in the group of HIV-infected recipients (P = 0.079). The HIV-positive recipient group presented a higher incidence of treated AR (P = 0.036) and DGF (P = 0.044). Chronic Kidney Disease Epidemiology Collaboration estimated that glomerular filtration rate was similar at 6 months (P = 0.374) and at 12 months (P = 0.957). The median number of infections per patient was higher in the HIV-infected group (P = 0.018). The 1-year patient survival (P < 0.001) and graft survival (P = 0.004) were lower, but acceptable, in the group of HIV-infected patients. CONCLUSIONS: In the Brazilian experience, despite somewhat inferior outcomes, kidney transplantation is an adequate therapy for selected HIV-infected recipients.

Long-term T cell memory requires the surface expression of self-peptide/major histocompatibility complex molecules.

How memory T cells are maintained in vivo is poorly understood. To address this problem, a male-specific peptide (H-Y) was identified and used to activate female anti-H-Y T cells in vitro. Anti-H-Y T cells survived in vivo for at least 70 days in the absence of antigen. This persistence was not because of the intrinsic ability of memory T cells to survive in vivo. Instead, the survival and function of adoptively transferred memory cells was found to require transporter of antigen protein 1-dependent expression of self-peptide/major histocompatibility complex class I molecules in recipient animals. Therefore, it appears that the level of T cell receptor engagement provided by transporter of antigen protein 1-dependent, self-peptide/major histocompatibility complexes is sufficient to maintain the long-term survival and functional phenotype of memory cells in the absence of persistent antigen. These data suggest that positive selection plays a role not only in T cell development but also in the maintenance of T cell memory.

Limits to the differential avidity model of T cell selection in the thymus.

It has been postulated that the critical feature that determines the developmental fate of an immature thymocyte is the avidity of interaction between thymocyte TCR and peptide/MHC molecules on thymic stromal cells. However, it is possible that certain innate properties of peptides predispose them to triggering only positive or negative selection irrespective of their density on thymic stromal cells. To distinguish between these hypotheses, we examined the ability of several different peptides to induce the positive and negative selection of TCR transgenic (P14) antilymphocytic choriomeningitis virus (LCMV) CTLs in fetal thymus organ cultures (FTOC) from TAP1+ and TAP1- mice. We found that only relatively weak agonist peptides could induce the positive selection of anti-LCMV CTLs. A nonagonist peptide could induce positive selection but not negative selection; however, a weak agonist peptide could induce the positive selection of anti-LCMV CTLs in P14 TAP1- FTOC and negative selection in P14 TAP1+ FTOC. These data imply that there are upper and lower limits for the affinity of a peptide in triggering positive or negative selection, but that for peptides of intermediate affinity the overall avidity of interaction with the P14 TCR is the critical parameter in determining the developmental fate of thymocytes. Our observations also suggest a prominent role for low affinity self peptides in selecting a function repertoire of CD8+ T cells.

Specific recognition of thymic self-peptides induces the positive selection of cytotoxic T lymphocytes.

To understand how thymic selection gives rise to T cells that are capable of major histocompatibility complex (MHC)-restricted recognition of antigen but are tolerant of self, we directly examined how peptide/MHC ligands expressed on thymic epithelial cells trigger the positive selection of immature thymocytes. We demonstrate that abundant self-peptides, purified from the H-2D(b) molecules of thymic epithelial cells, are specifically recognized during the positive selection of CD8+ T cells, implying that positive selection generates a repertoire of T cells that is weakly self-reactive. We also found that this recognition is somewhat cross-reactive, thereby providing an explanation for how the specific recognition of a limited repertoire of thymic self-peptides can select a diverse repertoire of T cells.