A major challenge in transplantation medicine is controlling the very strong immune responses to foreign antigens that are responsible for graft rejection. Although immunosuppressive drugs efficiently inhibit acute graft rejection, a substantial proportion of patients suffer chronic rejection that ultimately leads to functional loss of the graft. Induction of immunological tolerance to transplants would avoid rejection and the need for lifelong treatment with immunosuppressive drugs. Tolerance to self-antigens is ensured naturally by several mechanisms; one major mechanism depends on the activity of regulatory T lymphocytes. Here we show that in mice treated with clinically acceptable levels of irradiation, regulatory CD4+CD25+Foxp3+ T cells stimulated in vitro with alloantigens induced long-term tolerance to bone marrow and subsequent skin and cardiac allografts. Regulatory T cells specific for directly presented donor antigens prevented only acute rejection, despite hematopoietic chimerism. By contrast, regulatory T cells specific for both directly and indirectly presented alloantigens prevented both acute and chronic rejection. Our findings demonstrate the potential of appropriately stimulated regulatory T cells for future cell-based therapeutic approaches to induce lifelong immunological tolerance to allogeneic transplants.

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The AST/ALT ratio is both reproducible and transportable in patients with HCV-related CLD. The AST/ALT ratio is correlated with both histologic stage and clinical evaluation. Progressive liver functional impairment is reflected by an increase in the AST/ALT ratio. Noninvasive evaluation by means of the combined AST/ALT ratio and PLT assessment misclassifies only a few cirrhotic patients. In cirrhotic patients, the AST/ALT ratio provides medium-term prognostic information that is no different from that provided by established prognostic scores.

Background: Indices for predicting survival are essential for assessing prognosis and assigning priority for liver transplantation in patients with liver cirrhosis. The model for end stage liver disease (MELD) has been proposed as a tool to predict mortality risk in cirrhotic patients. However, this model has not been validated beyond its original setting. Aim: To evaluate the short and medium term survival prognosis of a European series of cirrhotic patients by means of MELD compared with the Child-Pugh score. We also assessed correlations between the MELD scoring system and the degree of impairment of liver function, as evaluated by the monoethylglycinexylidide (MEGX) test. Patients and methods: We retrospectively evaluated survival of a cohort of 129 cirrhotic patients with a follow up period of at least one year. The Child-Pugh score was calculated and the MELD score was computed according to the original formula for each patient. All patients had undergone a MEGX test. Multivariate analysis was performed on all variables to identify the parameters independently associated with one year and six month survival. MELD values were correlated with both Child-Pugh scores and MEGX test results. Results: Thirty one patients died within the first year of follow up. Child-Pugh and MELD scores, and MEGX serum levels were significantly different among patients who survived and those who died. Serum creatinine, international normalised ratio, and MEGX 60 were independently associated with six month mortality while the same variables and the presence of ascites were associated with one year mortality. MELD scores showed significant correlations with both MEGX values and Child-Pugh scores.

Most T lymphocytes, including regulatory T cells (Treg cells), differentiate in the thymus. The age-dependent involution of this organ leads to decreasing production of T cells. Here we found that the output of new Treg cells from the thymus decreased substantially more than that of conventional T cells. Peripheral mouse and human Treg cells recirculated back to the thymus, where they constituted a large proportion of the pool of Treg cells and displayed an activated and differentiated phenotype. In the thymus, the recirculating cells exerted their regulatory function by inhibiting interleukin 2 (IL-2)-dependent de novo differentiation of Treg cells. Thus, Treg cell development is controlled by a negative feedback loop in which mature progeny cells return to the thymus and restrain development of precursors of Treg cells.

SummaryInvariant chain (Ii) contributes in a number of distinct ways to the proper functioning of major histocompatibility complex (MHC) class II molecules. These include promoting effective association and folding of newly synthesized MHC class II c~ and B subunits, increasing transit of assembled heterodimers out of the endoplasmic reticulum (ER), inhibiting class II peptide binding, and facilitating class II movement to or accumulation in endosomes/lysosomes. Although the cytoplasmic tail of Ii makes a key contribution to the endocytic localization of class II, the relationship between the structure of Ii and its other diverse functions remains unknown. We show here that two thirds of the lumenal segment of Ii can be eliminated without affecting its contributions to the secretory pathway events of class II folding, ElK to Golgi transport, or inhibition of peptide binding. These same experiments reveal that a short (25 residue) contiguous internal segment of Ii (the CLIP region), frequently found associated with purified MHC class II molecules, is critical for all three functions. Together with other recent findings, these results raise the possibility that the contributions of Ii to the early postsynthetic behavior of class II may depend on its interaction with the class II binding site. This would be consistent with the intracellular behavior of unoccupied MHC class I and class II molecules as incompletely folded proteins and imply a related structural basis for the similar contributions of Ii to class II and of short peptides to class I assembly and transport.U 'pon synthesis and translocation into the endoplasmic reticulum (ER) 1, the component chains of class I and class II MHC molecules need to acquire a transport-competent conformation for effective post-ER transport. To achieve proper folding and a stable heavy chain-B2 microglobulin interaction suitable for secretory pathway transit, MHC class I molecules require binding site occupancy with short peptides primarily generated in the cytosol and imported into the ER via TAP (1-3). In contrast, MHC class II molecules assemble as a stoichiometric complex with trimers of the type II integral membrane glycoprotein invariant chain (Ii) (4). In the secretory pathway, this association with Ii has effects on the properties of class II analogous to those resulting from peptide interaction with class I (3). Thus, interaction with intact Ii contributes to efficient, stable association of the class II c~ and j8 subunits in the ER (5, 6), promotes the transport of class II oe/~8 heterodimers from the ER through the Golgi complex (5, 7-10), and inhibits the binding of other ligands (peptides) to the class II molecules (11-13). Whether these multiple effects of Ii require the entire molecule or are medi1Abbreviations used in this paper: endo H, endoglycosidase H; ER, endoplasmic reticulum; Ii, invariant chain. ated by one or more structurally independent subregions of the protein is presently unknown. A particularly intriguing question is whether the effects of Ii on ...

Owing to difficulties in measuring ventilation symmetry, good evidence of different right/left respiratory movements has not yet been provided. We investigated VT differences between paretic and healthy sides during quiet breathing, voluntary hyperventilation, and hypercapnic stimulation in patients with hemiparesis. We studied eight patients with hemiparesis and nine normal sex- and age-matched subjects. Right- and left-sided VT was reconstructed using optoelectronic plethysmography. In control subjects, no asymmetry was found in the study conditions. VTs of paretic and healthy sides were similar during quiet breathing, but paretic VT was lower during voluntary hyperventilation in six patients and higher during hypercapnic stimulation in eight patients (p = 0.02). The ventilatory response to hypercapnic stimulation was higher on the paretic than on the healthy side (p = 0.012). In conclusion, hemiparetic stroke produces asymmetric ventilation with an increase in carbon dioxide sensitivity and a decrease in voluntary ventilation on the paretic side.

Thymus-derived regulatory T lymphocytes of CD4 ؉ CD25 ؉ phenotype regulate a large variety of beneficial and deleterious immune responses and can inhibit lethal graft-versus-host disease in rodents. In vitro, CD4 ؉ CD25 ؉ T cells require specific major histocompatibility complex (MHC)/peptide ligands for their activation, but once activated they act in an antigen-nonspecific manner. In vivo, regulatory T cells are also activated in an antigen-specific fashion, but nothing is known about antigen specificity of their suppressor-effector function. Here we show that CD4 ؉ CD25 ؉ regulatory T lymphocytes isolated from naive mice and activated in vitro with allogeneic antigenpresenting cells (APCs) induced specific long-term tolerance to bone marrow grafts disparate for major and minor histocompatibility antigens; whereas "target" bone marrow was protected, third-party bone marrow was rejected. Importantly, in mice injected with a mix of target and thirdparty bone marrows, protection and rejection processes took place simultaneously. These results indicate that CD4 ؉ CD25 ؉ regulatory T cells can act in an antigenspecific manner in vivo. Our results suggest that CD4 ؉ CD25 ؉ regulatory T cells could in the future be used in clinical settings to induce specific immunosuppression. ( IntroductionDue to the random rearrangements of genes encoding T-and B-lymphocyte antigen receptors, a significant number of autospecific and potentially autoreactive lymphocytes develop in primary lymphoid organs. [1][2][3] Central tolerance (ie, induced in primary lymphoid organs) eliminates (by deletion) or functionally inactivates (by induction of anergy) such dangerous lymphocytes. In absence of central tolerance induction, a strongly self-reactive T-cell repertoire develops. 4,5 However, when central tolerance is partially defective, self-tolerance can be maintained by peripheral mechanisms. [6][7][8] Several types of peripheral tolerance mechanisms control lymphocytes having escaped central tolerance and are known to play a crucial role in preventing autoimmunity (for reviews see Sprent et al 6 and Stockinger 9 ).One of these peripheral tolerance mechanisms was discovered using the day-3 thymectomy model of multiorgan autoimmunity in mice. 10 The pathology can be prevented by injection of CD4 ϩ CD25 ϩ lymphocytes, which appear after day 3 of life in the peripheral lymphoid organs of normal mice. CD4 ϩ CD25 ϩ regulatory T cells do not only inhibit autoimmunity, they can also inhibit experimental inflammatory bowel disease induced by injection of CD4 ϩ CD45RB high cells into severe combined immunodeficiency (SCID) mice or recombination-activating gene (RAG)-deficient animals. 11 Moreover, they contribute to the fine control of immunity to infectious agents such as parasites and viruses. 12,13 An undesired side effect of the activity of CD4 ϩ CD25 ϩ regulatory T lymphocytes is the occasional incapacity of the immune system to eliminate tumor cells. 14,15 Therefore, regulatory T lymphocytes play a crucial role in the pathophysiologic mai...