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Patients with recurrent or metastatic cancer commonly suffer from debilitating toxicity associated with conventional treatment modalities, as well as disease-related symptoms, often with a concomitant negative impact on health-related quality of life (HRQoL). Patient-reported outcomes (PROs) provide important insights into the patient experience in clinical trials. Nivolumab is a programmed death-1 receptor inhibitor that extends survival in patients with recurrent or metastatic disease in multiple tumor types. In this review, we summarize published PRO analyses from eight phase II-IV clinical trials with nivolumab for the treatment of melanoma, non-small cell lung cancer, renal cell carcinoma (RCC), and squamous cell carcinoma of the head and neck (SCCHN). Symptom burden, physical functioning, and HRQoL were measured using generic, cancer-specific, and tumor type-specific validated PRO instruments. Nivolumab showed sustained stabilization across all tumor types and, in some cases, clinically meaningful improvement in HRQoL, whereas standard of care therapies often led to deteriorations. Exploratory analyses found a positive correlation between baseline HRQoL scores and overall survival in RCC, and between baseline HRQoL scores and healthcare resource utilization in SCCHN, suggesting that patient-reported symptoms at treatment initiation may have clinical value. In the era of value-based oncology care, stakeholders are increasingly interested in PRO findings to guide clinical, regulatory, and reimbursement decisions. However, missing data remain a significant challenge in PRO analyses, including in nivolumab trials. Future clinical trials in immuno-oncology should incorporate PRO data collection, including beyond treatment discontinuation or trial completion to assess the long-term effects of treatment on HRQoL., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: To use econometric methods to assess comparative overall survival of patients with metastatic renal cell carcinoma (mRCC) managed with initial cytoreductive nephrectomy (CN) vs initial systemic therapy. Randomized data demonstrate improved survival for CN preceding cytokine-based therapy in mRCC. This benefit may be attenuated in the contemporary mRCC era given more effective systemic therapies., Methods: Patients over age 65 with mRCC from the Surveillance, Epidemiology, and End Results registries linked with Medicare claims from 2006 to 2011 were categorized by initial treatment. We applied sequential survival analysis methods to assess the association between initial CN and overall survival (OS) including Cox proportional hazards models, propensity scoring, and instrumental variable analysis to account for measured and unmeasured selection bias., Results: Of 537 patients analyzed, 190 had initial CN followed by targeted therapy and 347 had initial targeted therapy. Median OS in the initial CN group was 17.4 months (interquartile range 9.8-32.0), compared with 9.2 months (interquartile range 4.3-18.0) for initial targeted therapy. Cox proportional hazards analysis revealed initial CN was associated with improved OS (hazard ratio 0.50, 95% confidence interval [CI] 0.38-0.65). Propensity matching demonstrated a survival advantage for initial CN of 5.8 months (95% CI 1.9-9.7). Accounting for unmeasured confounding with instrumental variable analysis demonstrated a trend toward improved survival with initial CN (hazard ratio 0.29 [95% CI 0.08-1.00])., Conclusion: Initial CN is associated with improved survival compared with initial systemic therapy in a contemporary population-based mRCC cohort., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: The randomized, phase 3 CheckMate 025 study of nivolumab (n=410) versus everolimus (n=411) in previously treated adults (75% male; 88% white) with advanced renal cell carcinoma (aRCC) demonstrated significantly improved overall survival (OS) and objective response rate (ORR)., Objective: To investigate which baseline factors were associated with OS and ORR benefit with nivolumab versus everolimus., Design, Setting, and Participants: Subgroup OS analyses were performed using Kaplan-Meier methodology. Hazard ratios were estimated using the Cox proportional hazards model., Intervention: Nivolumab 3mg/kg every 2 wk or everolimus 10mg once daily., Results and Limitations: The minimum follow-up was 14 mo. Baseline subgroup distributions were balanced between nivolumab and everolimus arms. Nivolumab demonstrated an OS improvement versus everolimus across subgroups, including Memorial Sloan Kettering Cancer Center (MSKCC) and International Metastatic Renal Cell Carcinoma Database Consortium risk groups; age <65 and ≥65 yr; one and two or more sites of metastases; bone, liver, and lung metastases; number of prior therapies; duration of prior therapy; and prior sunitinib, pazopanib, or interleukin-2 therapy. The benefit with nivolumab versus everolimus was noteworthy for patients with poor MSKCC risk (hazard ratio 0.48, 95% confidence interval 0.32-0.70). The mortality rate at 12 mo for all subgroups was lower with nivolumab compared with everolimus. ORR also favored nivolumab. The incidence of grade 3 or 4 treatment-related adverse events across subgroups was lower with nivolumab. Limitations include the post hoc analysis and differing sample sizes between groups., Conclusion: The trend for OS and ORR benefit with nivolumab for multiple subgroups, without notable safety concerns, may help to guide treatment decisions, and further supports nivolumab as the standard of care in previously treated patients with aRCC., Patient Summary: We investigated the impact of demographic and pretreatment features on survival benefit and tumor response with nivolumab versus everolimus in advanced renal cell carcinoma (aRCC). Survival benefit and response were observed for multiple subgroups, supporting the use of nivolumab as a new standard of care across a broad range of patients with previously treated aRCC. The trial is registered on ClinicalTrials.gov as NCT01668784., (Copyright © 2017 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

Importance: Response patterns with immunotherapy may differ from those of other treatments. This warrants further investigation because some patients may benefit from continued immunotherapy beyond Response Evaluation Criteria in Solid Tumors (RECIST)-defined first progression., Objective: To evaluate the safety and potential benefit of treatment with nivolumab, a programmed cell death 1 immune checkpoint inhibitor, beyond investigator-assessed first progression in patients with metastatic renal cell carcinoma (mRCC)., Design, Setting, and Participants: Subgroup analysis of a blinded, randomized, multicenter, phase 2 dose-ranging trial initiated May 31, 2011, including patients with clear-cell mRCC previously treated with antiangiogenic therapy. Data cutoffs for this subgroup analysis were May 15, 2013, for progression-free survival and objective response rate and March 5, 2014, for overall survival and duration of response. In this analysis, patients treated beyond first progression received their last dose of nivolumab more than 6 weeks after RECIST-defined progression, and patients not treated beyond first progression discontinued nivolumab before or at RECIST-defined progression., Interventions: Nivolumab 0.3, 2, or 10 mg/kg intravenously every 3 weeks., Main Outcomes and Measures: Safety and efficacy of nivolumab treatment., Results: Of 168 patients (median [range] age, 61 [37-81] years; 72% male) randomized to nivolumab, 154 experienced progression (36 were treated beyond first progression, 26 were treated beyond first progression for ≤6 weeks, and 92 were not treated beyond first progression), 13 were treated and did not experience progression, and 1 was not treated. Prior to first progression, the RECIST-defined objective response rate was 14% (5 patients) and 16% (15 patients), and median progression-free survival was 4.2 (95% CI, 2.8-5.5) and 2.6 (95% CI, 1.5-3.9) months in patients treated and not treated beyond progression, respectively. Following initial progression, 25 (69%) patients treated beyond progression experienced subsequent tumor reduction or stabilization in target lesion size. The incidence of treatment-related adverse events was higher in patients treated beyond progression (n = 29 [81%]) vs those not treated beyond progression (n = 61 [66%]); however, after adjusting for length of treatment exposure, incidence was lower in patients treated beyond progression (322.9 vs 518.7 incidence rate/100 patient-years for patients treated vs not treated beyond progression)., Conclusions and Relevance: In this subgroup analysis, a proportion of patients who continued treatment beyond RECIST-defined first progression demonstrated sustained reductions in tumor burden or stabilization in the size of target lesions, with an acceptable safety profile. Further analysis will help define the clinical benefit for patients with mRCC treated with nivolumab beyond progression., Trial Registration: clinicaltrials.gov Identifier: NCT01354431.

Background: Nivolumab, a programmed death 1 (PD-1) checkpoint inhibitor, was associated with encouraging overall survival in uncontrolled studies involving previously treated patients with advanced renal-cell carcinoma. This randomized, open-label, phase 3 study compared nivolumab with everolimus in patients with renal-cell carcinoma who had received previous treatment., Methods: A total of 821 patients with advanced clear-cell renal-cell carcinoma for which they had received previous treatment with one or two regimens of antiangiogenic therapy were randomly assigned (in a 1:1 ratio) to receive 3 mg of nivolumab per kilogram of body weight intravenously every 2 weeks or a 10-mg everolimus tablet orally once daily. The primary end point was overall survival. The secondary end points included the objective response rate and safety., Results: The median overall survival was 25.0 months (95% confidence interval [CI], 21.8 to not estimable) with nivolumab and 19.6 months (95% CI, 17.6 to 23.1) with everolimus. The hazard ratio for death with nivolumab versus everolimus was 0.73 (98.5% CI, 0.57 to 0.93; P=0.002), which met the prespecified criterion for superiority (P≤0.0148). The objective response rate was greater with nivolumab than with everolimus (25% vs. 5%; odds ratio, 5.98 [95% CI, 3.68 to 9.72]; P<0.001). The median progression-free survival was 4.6 months (95% CI, 3.7 to 5.4) with nivolumab and 4.4 months (95% CI, 3.7 to 5.5) with everolimus (hazard ratio, 0.88; 95% CI, 0.75 to 1.03; P=0.11). Grade 3 or 4 treatment-related adverse events occurred in 19% of the patients receiving nivolumab and in 37% of the patients receiving everolimus; the most common event with nivolumab was fatigue (in 2% of the patients), and the most common event with everolimus was anemia (in 8%)., Conclusions: Among patients with previously treated advanced renal-cell carcinoma, overall survival was longer and fewer grade 3 or 4 adverse events occurred with nivolumab than with everolimus. (Funded by Bristol-Myers Squibb; CheckMate 025 ClinicalTrials.gov number, NCT01668784.).

Objective: To evaluate population-based survival trends, compared to optimistic trial benchmarks, in metastatic renal cell carcinoma (mRCC). Advances in medical therapy for mRCC may be associated with survival improvements. Yet, targeted therapy trial results focus on patients with favorable-risk mRCC and may not be well disseminated at the population level., Methods: Surveillance, Epidemiology, and End Results identified adult mRCC patients diagnosed between 1990 and 2009. Survival was analyzed by treatment era (cytokine, 1990-2005; targeted therapy, 2006-2009) and stratified by histology. Multivariate Cox regression identified factors independently associated with overall survival., Results: We identified 14,521 eligible patients. For clear cell mRCC (N = 4149), median survival improved from 11 to 14 months before and after targeted therapy (P <.001). For RCC with sarcomatoid features (N = 608) and RCC not otherwise specified (N = 8860), survival did not change (median survival 4 months for both). For non-clear cell subtypes (N = 904), median survival improved from 7 to 9 months (P = .008). On multivariate analysis, factors associated with increased overall survival were as follows: treatment in the targeted era (hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.84-0.91), clear cell histology (HR, 0.76; 95% CI, 0.73-0.80), and receipt of surgery (HR, 0.43; 95% CI, 0.41-0.46)., Conclusion: Population-based mRCC median survival improved but to a lesser degree than that reported in clinical trials. This represents opportunity for quality improvement in histologically guided care, use of cytoreductive nephrectomy, and development of strategies for trial-ineligible, poor-risk patients., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The 10-year survival rate for patients with metastatic melanoma has historically been less than 10%. However, recent successes with immunotherapy and BRAF-targeted therapy have ushered in a new era in systemic therapy of this disease. These therapies have been associated with significant improvements in patient outcomes in several randomized phase III trials. Not only have these breakthroughs increased the likelihood of long-term survival in patients with melanoma, but they have also spurred the investigation of a new generation of agents for treatment of melanoma. This article reviews both current options for systemic treatment of metastatic melanoma and promising investigational approaches. We also discuss important considerations in choosing among systemic therapy options, to match the unique goals of therapy for individual patients.

Innovative therapies are needed for advanced Non-Small Cell Lung Cancer (NSCLC). We have undertaken a genomics based, hypothesis driving, approach to query an emerging potential that epigenetic therapy may sensitize to immune checkpoint therapy targeting PD-L1/PD-1 interaction. NSCLC cell lines were treated with the DNA hypomethylating agent azacytidine (AZA - Vidaza) and genes and pathways altered were mapped by genome-wide expression and DNA methylation analyses. AZA-induced pathways were analyzed in The Cancer Genome Atlas (TCGA) project by mapping the derived gene signatures in hundreds of lung adeno (LUAD) and squamous cell carcinoma (LUSC) samples. AZA up-regulates genes and pathways related to both innate and adaptive immunity and genes related to immune evasion in a several NSCLC lines. DNA hypermethylation and low expression of IRF7, an interferon transcription factor, tracks with this signature particularly in LUSC. In concert with these events, AZA up-regulates PD-L1 transcripts and protein, a key ligand-mediator of immune tolerance. Analysis of TCGA samples demonstrates that a significant proportion of primary NSCLC have low expression of AZA-induced immune genes, including PD-L1. We hypothesize that epigenetic therapy combined with blockade of immune checkpoints - in particular the PD-1/PD-L1 pathway - may augment response of NSCLC by shifting the balance between immune activation and immune inhibition, particularly in a subset of NSCLC with low expression of these pathways. Our studies define a biomarker strategy for response in a recently initiated trial to examine the potential of epigenetic therapy to sensitize patients with NSCLC to PD-1 immune checkpoint blockade.

Long-term engraftment of allogeneic cells necessitates eluding immune-mediated rejection, which is currently achieved by matching for human leukocyte antigen (HLA) expression, immunosuppression, and/or delivery of donor-derived cells to sanctuary sites. Genetic engineering provides an alternative approach to avoid clearance of cells that are recognized as "non-self" by the recipient. To this end, we developed designer zinc finger nucleases and employed a "hit-and-run" approach to genetic editing for selective elimination of HLA expression. Electro-transfer of mRNA species coding for these engineered nucleases completely disrupted expression of HLA-A on human T cells, including CD19-specific T cells. The HLA-A(neg) T-cell pools can be enriched and evade lysis by HLA-restricted cytotoxic T-cell clones. Recognition by natural killer cells of cells that had lost HLA expression was circumvented by enforced expression of nonclassical HLA molecules. Furthermore, we demonstrate that zinc finger nucleases can eliminate HLA-A expression from embryonic stem cells, which broadens the applicability of this strategy beyond infusing HLA-disparate immune cells. These findings establish that clinically appealing cell types derived from donors with disparate HLA expression can be genetically edited to evade an immune response and provide a foundation whereby cells from a single donor can be administered to multiple recipients.

Peptides that are presented by MHC class I (MHC-I) are processed from two potential sources, as follows: newly synthesized endogenous proteins for direct presentation on the surface of most nucleated cells and exogenous proteins for cross-presentation typically by professional APCs. In this study, we present data that implicate the nonclassical HLA-F and open conformers of MHC-I expressed on activated cells in a pathway for the presentation of exogenous proteins by MHC-I. This pathway is distinguished from the conventional endogenous pathway by its independence from TAP and tapasin and its sensitivity to inhibitors of lysosomal enzymes, and further distinguished by its dependence on MHC-I allotype-specific epitope recognition for Ag uptake. Thus, our data from in vitro experiments collectively support a previously unrecognized model of Ag cross-presentation mediated by HLA-F and MHC-I open conformers on activated lymphocytes and monocytes, which may significantly contribute to the regulation of immune system functions and the immune defense.

Adaptive immune responses appear to influence the natural history of cancer progression, as well as therapeutic outcomes, in cancer patients. However, accumulating evidence suggests resistance mechanisms exploited by tumors may play a dominant role in limiting the effectiveness of T cell-mediated cancer therapies. Inhibitory coreceptors expressed by T lymphocytes, or so-called immune checkpoints, are now recognized to play critical roles in regulating the termination of adaptive immune responses. An overview of early-phase trial results distinguish blocking antibodies targeting inhibitory coreceptors as a highly promising approach to cancer immunotherapy for patients with advanced clear cell renal cell carcinoma. Prospects for advanced-phase clinical testing and novel therapy combinations with immune checkpoint blocking agents are discussed.

The tumor antigen 5T4 is frequently expressed at high levels on renal cell carcinoma (RCC) and other epithelial carcinomas. Surveys of normal tissues demonstrate abundant 5T4 expression on placental trophoblast cells with limited expression elsewhere. 5T4 is the target for a therapeutic cancer vaccine (MVA-5T4) that elicits 5T4-specific serological, proliferative, and cytotoxic T lymphocyte (CTL) responses. However, the antitumor activity of 5T4-specific CTL has not been extensively characterized. CD8 T cells from HLA-A2 healthy donors (n=4) or RCC patients (n=2) were stimulated in vitro with the HLA-A2-binding nonamer peptides 5T417-25 or 5T497-105 and screened by flow cytometry with specific tetramers (TET). CD8/TET T-cell clones specific for 5T417-25 or 5T497-105 peptide were isolated from 4/6 and 1/4 donors, respectively. A subset of clones specific for 5T417-25 was cytolytic for MVA-5T4-infected HLA-A2 EBV-transformed lymphoblastoid cell line target cells and for constitutively HLA-A2-expressing and 5T4-expressing RCC tumor cell lines (including A498 RCC). In a xenoengraftment assay, the coinoculation of a representative 5T417-25-specific CTL clone with A498 RCC tumors cells into immune-deficient mice completely prevented growth of A498 tumors. Taken together, these data demonstrate high-avidity CD8 CTL able to recognize the naturally processed 5T417-25 epitope on RCC tumor cells including putative tumor-initiating cells are present in peripheral blood of both healthy donors and RCC patients. CD8T-cell immunity targeting 5T417-25 is therefore of substantial interest both as a potential target for further development of vaccination or adoptive cellular immunotherapy and for immune monitoring studies in association with nonspecific immunotherapies.

Introduction: The first series of patients with metastatic renal cell carcinoma (RCC) treated by non-myeloablative allogeneic hematopoietic cell transplantation (HCT) was reported in 2000 and demonstrated an allogeneic graft-versus-tumor (GVT) effect that encouraged further investigation of this approach. However, the past 10 years have also witnessed profound changes in the medical management of metastatic RCC with the introduction of targeted therapies directed against VEGF or mammalian target of rapamycin (mTOR) signaling pathways creating uncertainty about a continued role for allogeneic HCT in the treatment of RCC., Areas Covered: A total of 21 published reports describing clinical outcomes for 398 patients with metastatic RCC treated by allogeneic HCT compiled herein provide a composite overview of the world wide experience for key efficacy and toxicity outcomes. Review of correlative studies that identify donor-derived T cells as mediators of RCC-specific GVT effects offers insight into both the potential as well as the technical barriers to the delivery of antigen-specific post-transplant cellular therapy or vaccination designed to augment the allogeneic GVT effect., Expert Opinion: The future development of non-myeloablative allogeneic HCT for metastatic RCC will require novel treatment protocols designed to augment and sustain post-transplant GVT effects against RCC to generate renewed enthusiasm for this approach.

Background: The tumor-associated antigen 5T4 is expressed on a high percentage of human carcinomas and has limited expression in normal tissues. A recombinant pox virus vector expressing this antigen, modified vaccinia Ankara (MVA)-5T4, has been tested as a cancer vaccine., Objective: Treatment with MVA-5T4 has been studied both as a single agent and in combination with standard chemo-, biologic- or targeted-therapies in patients with advanced colorectal cancer, renal cell carcinoma (RCC) or hormone-refractory prostate cancer., Methods: This review summarizes data from clinical studies with MVA-5T4 reported in published manuscripts, meeting abstracts or posted on websites relevant to clinical trials or MVA-5T4., Results/conclusion: Vaccination with MVA-5T4 is well tolerated and elicits 5T4-specific humoral and/or cellular responses in most of the treated patients. Retrospective analyses of Phase II studies have suggested a positive association between immune responses to 5T4 and favorable clinical outcomes. A continuing Phase III, double-blind, placebo-controlled trial seeks to confirm a positive association between vaccination with MVA-5T4 and survival in patients with advanced RCC.

Purpose: Tumor regression has been observed in some patients with metastatic renal cell carcinoma (RCC) after nonmyeloablative allogeneic hematopoietic cell transplantation (HCT). Cellular and molecular characterization of antigens recognized by tumor-reactive T cells isolated from responding patients could potentially provide insight into the mechanisms of tumor regression., Experimental Design: CD8+ CTL clones that recognized a novel RCC-associated minor histocompatibility (H) antigen presented by HLA-A*0201 were isolated from two patients with metastatic RCC who experienced tumor regression or stable disease following nonmyeloablative allogeneic HCT. These clones were used to screen a cDNA library and isolate the unique cDNA encoding the antigen., Results: An alternative open reading frame in the C19orf48 gene located on chromosome 19q13 encodes the HLA-A*0201-restricted minor H antigen recognized by the RCC-reactive T cells. The differential T-cell recognition of donor- and recipient-derived target cells is attributable to a nonsynonymous single-nucleotide polymorphism within the nucleotide interval that encodes the antigenic peptide. Assays for gene expression and CTL recognition showed that the C19orf48-encoded peptide is widely expressed in renal tumors and solid tumors of other histologies. The antigenic peptide can be processed for CTL recognition via both TAP-dependent and TAP-independent pathways., Conclusions: Donor T-cell responses against the HLA-A*0201-restricted minor H antigen encoded by C19orf48 may contribute to RCC regression after MHC-matched allogeneic HCT.

CD8-positive T lymphocytes recognize peptides that are usually derived from the degradation of cellular proteins and are presented by class I molecules of the major histocompatibility complex. Here we describe a human minor histocompatibility antigen created by a polymorphism in the SP110 nuclear phosphoprotein gene. The antigenic peptide comprises two noncontiguous SP110 peptide segments spliced together in reverse order to that in which they occur in the predicted SP110 protein. The antigenic peptide could be produced in vitro by incubation of precursor peptides with highly purified 20S proteasomes. Cutting and splicing probably occur within the proteasome by transpeptidation.

Purpose: This phase I trial assessed the safety, efficacy, and immunologic responses to minor histocompatibility antigens following nonmyeloablative allogeneic hematopoietic cell transplantation as treatment for metastatic renal cell carcinoma., Experimental Design: Eight patients received conditioning with fludarabine and low-dose total body irradiation followed by hematopoietic cell transplantation from an HLA-matched sibling donor. Cyclosporine and mycophenolate mofetil were administered as posttransplant immunosuppression. Patients were monitored for donor engraftment of myeloid and lymphoid cells, for clinical response by serial imaging, and for immunologic response by in vitro isolation of donor-derived CD8(+) CTLs recognizing recipient minor histocompatibility (H) antigens., Results: All patients achieved initial mixed hematopoietic chimerism with two patients rejecting their graft and recovering host hematopoiesis. Four patients developed acute, grade 2 to 3, graft-versus-host disease and four patients developed extensive chronic graft-versus-host disease. Five patients had progressive disease, two patients had stable disease, and one patient experienced a partial response after receiving donor lymphocyte infusions and IFN-alpha. CD8(+) CTL clones recognizing minor H antigens were isolated from five patients studied. Clones from three patients with a partial response or stable disease recognized antigens expressed on renal cell carcinoma tumor cells., Conclusions: Treatment of metastatic renal cell carcinoma with allogeneic hematopoietic cell transplantation after nonmyeloablative conditioning with fludarabine/total body irradiation is feasible and may induce tumor regression or stabilization in some patients. CD8(+) CTL-recognizing minor H antigens on tumor cells can be isolated posttransplant and could contribute to the graft-versus-tumor effect. Such antigens may represent therapeutic targets for posttransplant vaccination or adoptive T-cell therapy to augment the antitumor effects of allogeneic hematopoietic cell transplantation.

The Ag receptors on CD8+ CTL recognize foreign antigenic peptides associated with cell surface MHC class I molecules. Peptides derived from self proteins are also normally presented by MHC class I molecules. Here we report that an H-2Kd-restricted murine CD8+ CTL clone directed to an influenza hemagglutinin epitope can recognize a peptide derived from the murine mitochondrial aconitase enzyme in association with H-2Kd molecules. Surprisingly, this self peptide is not normally displayed on the cell surface associated with the restricting MHC class I molecule. Several lines of evidence suggest that this self peptide, although requiring association with the Kd molecule for CTL recognition, is not associated with this or other MHC class I allele under physiologic conditions in intact cells. Rather, it is sequestered in the cytoplasm associated with a carrier protein and is released only upon cell disruption. These results suggest a means of restricting the entry of self peptide into the class I pathway. In addition, this finding raises the possibility that self peptides sequestered within the cell can, after release from damaged cells, interact with MHC class I molecules on bystander cells and trigger autoimmune injury by virus-specific CTLs during viral infection.

T cells are normally activated when the peptide for which they are specific is presented to them in the context of the appropriate major histocompatibility complex (MHC) (class I and Class II for CD8+ and CD4+ T cells, respectively). An increasing body of evidence indicates that structural homologues of the immunogenic peptide can partially activate or antagonize CD4+ T cells. CD8+ T cells may also be partially antagonized by such peptides, and self-derived peptides of this type may play a role in CD8+ T cell selection in the thymus. Activated CD8+ T cells lyse their targets by perforin-dependent granule exocytosis and by inducing apoptosis mediated by CD95 (also known as Fas or APO1) with its ligand (CD95L). Here we show that a clone of Kd-restricted CD8+ T cells specific for influenza haemagglutinin, which can also be activated in a crossreactive manner by a peptide derived from a myeloma tumour immunoglobulin heavy-chain variable region (IgVH) to kill by both routes, kills only by the CD95-CD95L pathway when stimulated by the corresponding germline IgVH peptide. As this germline IgVH peptide differs from the tumour peptide only at a single position buried in the MHC-binding groove, this indicates that CD95-CD95L-mediated killing can be triggered independently of the perforin-mediated pathway, and can be selectively affected by changes in MHC conformation.