T cell receptor (TCR) sequences are very diverse, with many more possible sequence combinations than T cells in any one individual1–4. Here we define the minimal requirements for TCR antigen specificity, through an analysis of TCR sequences using a panel of peptide and major histocompatibility complex (pMHC)-tetramer-sorted cells and structural data. From this analysis we developed an algorithm that we term GLIPH (grouping of lymphocyte interactions by paratope hotspots) to cluster TCRs with a high probability of sharing specificity owing to both conserved motifs and global similarity of complementarity-determining region 3 (CDR3) sequences. We show that GLIPH can reliably group TCRs of common specificity from different donors, and that conserved CDR3 motifs help to define the TCR clusters that are often contact points with the antigenic peptides. As an independent validation, we analysed 5,711 TCRβ chain sequences from reactive CD4 T cells from 22 individuals with latent Mycobacterium tuberculosis infection. We found 141 TCR specificity groups, including 16 distinct groups containing TCRs from multiple individuals. These TCR groups typically shared HLA alleles, allowing prediction of the likely HLA restriction, and a large number of M. tuberculosis T cell epitopes enabled us to identify pMHC ligands for all five of the groups tested. Mutagenesis and de novo TCR design confirmed that the GLIPH-identified motifs were critical and sufficient for shared-antigen recognition. Thus the GLIPH algorithm can analyse large numbers of TCR sequences and define TCR specificity groups shared by TCRs and individuals, which should greatly accelerate the analysis of T cell responses and expedite the identification of specific ligands.

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The role of NK cells following solid organ transplantation remains unclear. We examined NK cells in acute allograft rejection using a high responder model (DA → Lewis) of rat orthotopic liver transplantation.Recipient-derived NK cells infiltrated liver allografts early after transplantation. Since chemokines are important in the trafficking of cells to areas of inflammation, we determined the intragraft expression of chemokines known to attract NK cells. CCL3 was significantly increased in allografts at 6 h post-transplant as compared to syngeneic grafts whereas CCL2 and CXCL10 were elevated in both syngeneic and allogeneic grafts. CXCL10 and CX3CL1 were significantly upregulated in allografts by day 3 post-transplant as compared to syngeneic grafts suggesting a role for these chemokines in the recruitment of effector cells to allografts. Graft-infiltrating NK cells were shown to be a major source of IFN-c , and IFN-c levels in the serum were markedly increased, specifically in allograft recipients, by day 3 post-transplant. Accordingly, in the absence of NK cells the levels of IFN-c were significantly decreased. Furthermore, graft survival was significantly prolonged. These data suggest that IFNc -producing NK cells are an important link between the innate and adaptive immune responses early after transplantation.

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Human B cells are the primary targets of Epstein Barr virus (EBV) infection. In most cases EBV infection is asymptomatic because of a highly effective host immune response but some individuals develop self-limiting infectious mononucleosis, while others develop EBV-associated lymphoid or epithelial malignancies. The viral and immune factors that determine the outcome of infection are not understood. The EBV life cycle includes a lytic phase, culminating in the production of new viral particles, and a latent phase, during which the virus remains largely silent for the lifetime of the host in memory B cells. Thus, in healthy individuals there is a tightly orchestrated interplay between EBV and the host that allows the virus to persist. To promote viral persistence EBV has evolved a variety of strategies to modulate the host immune response including inhibition of immune cell function, blunting of apoptotic pathways, and interfering with antigen processing and presentation pathways. In this article we focus on mechanisms by which dysregulation of the host B cell, and immune modulation, by the virus can contribute to development of EBV+ B cell lymphomas.

T lymphocytes and immunoregulatory cytokines may be important in the host response to hepatitis C virus (HCV) infection. T-helper type 1 (Th1) cytokines (interleukin [IL]-2, interferon gamma [IFN-gamma]) are required for host antiviral immune responses, including cytotoxic T-cell generation and natural killer cell activation, while T-helper type 2 (Th2) cytokines (IL-4,IL-10) can inhibit the development of these effector mechanisms. In this study, the serum levels of Th1 and Th2 cytokines in patients (n = 23) infected with HCV were measured and compared with biochemical (alanine transaminase [ALT]) and viral (HCV RNA) indicators of infection. Serial cytokine levels were measured in a subset of 11 patients at 1 and 12 weeks during and at 1 week after interferon alfa (IFN-alpha) therapy (n = 33 samples). Levels of circulating IL-2, IL-4, IL-10, and IFN-gamma were significantly elevated in HCV patients versus normal controls (128 vs. 25 pg/mL, 3,045 vs. 29 pg/mL, 2,949 vs. 18 pg/mL, and 307 vs. 24 pg/mL respectively; P < .01). Treatment with IFN-alpha decreased the levels of IL-4 (321 +/- 224 pg/mL), and IL-10 (1,011 +/- 344 pg/mL), which paralleled a decrease in HCV RNA (114 +/- 27 vs. 25 +/- 20 Eq/ml X 10(5), pre- vs. post-IFN-alpha [12 weeks];P <.05). These findings indicate that an activated T-cell response, as manifest by increased circulating immunoregulatory cytokines, is present in patients with HCV liver disease. Furthermore, treatment with HCV liver disease. Furthermore, treatment with IFN-alpha diminishes the Th2 cytokine response. Thus, modulation of T-cell function and cytokine production may be one mechanism whereby IFN-alpha therapy results in reduced viral burden.

Keratin 8 and 18 (K8͞K18) mutations are found in patients with cryptogenic cirrhosis, but the role of keratin mutations in noncryptogenic cirrhosis and the incidence of keratin mutations in the general population are not known. We screened for K8͞K18 mutations in genomic DNA isolated from 314 liver explants of patients who primarily had noncryptogenic cirrhosis, and from 349 blood bank volunteers. Seven unique K8͞K18 mutations were found in 11 independent patients with biliary atresia, hepatitis B͞C, alcohol, primary biliary cirrhosis, and fulminant hepatitis. Seven of the 11 patients had mutations previously described in patients with cryptogenic cirrhosis: K8 Tyr-53 3 His, K8 Gly-61 3 Cys, and K18 His-127 3 Leu. The four remaining patients had mutations at one K8 and three other K18 new sites. Of the 349 blood bank control samples, only one contained the Tyr-53 3 His and one the Gly-61 3 Cys K8 mutations (P < 0.004 when comparing cirrhosis versus control groups). Two additional mutations were found in both the liver disease and blood bank groups and, hence, likely represent polymorphisms. Livers with keratin mutations had cytoplasmic filamentous deposits that were less frequent in livers without the mutations (P ‫؍‬ 0.03). Therefore, K8͞K18 are likely susceptibility genes for developing cryptogenic and noncryptogenic forms of liver disease.

Severe combined immunodeficient (SCID)' mice have an autosomal recessive defect that impairs the rearrangement of antigen receptor genes in lymphoid progenitors (1). Consequently, functional lymphocytes do not develop and these animals are severely lymphopenic (2, 3). Recent results have demonstrated that human fetal lymphoid tissue or peripheral blood lymphocytes from adults can survive in SLID mice, and this has raised the possibility that this model system would be valuable for the study ofthe human immune response and lymphohernatopoietic abnormalities (4, 5). A recent report suggests that acute infection of lymphoid cells in these so called SLID-hu mice with human immunodeficiency virus is possible, but the actual transfer of a lymphoid associated abnormality with human cells has not been reported (6).To further study this model we injected PBL obtained from both normal volunteers and patients with primary biliary cirrhosis (PBC) into SCID mice. PBC is a chronic autoimmune disease serologically characterized by the presence of autoantibodies to the mitochondrial oxo-dehydrogenase enzymes and histologically by the inflammation, specific obstruction, and eventual obliteration ofthe intrahepatic bile ducts (7-9).We report herein the transfer of PBC-like characteristics to the immunodeficient mice with PBLs from patients with PBC. Mitochondrial autoantibodies of human origin were present in the serum of the mice and biliary lesions that were apparently due to human lymphoid cells that had infiltrated around the intrahepatic bile ducts were present. A hepatic inflammatory reaction was also observed in mice that were recipients ofPBLs from normal donors, suggesting that human lymphoid cells react against murine tissues and cause a graft-vs .-host (GVH)-like disease in the animals. Materials and MethodsMice. Homozygous C.B-17 scid mice, designated SCID mice, were bred and maintained in a barrier