Fas/Apo1 mutations and autoimmune lymphoproliferative syndrome in a patient with type 2 autoimmune hepatitis

Pathogenesis of Autoimmune Hepatitis-Cellular and Molecular Mechanisms

Pediatric autoimmune liver disorders include autoimmune hepatitis (AIH), autoimmune sclerosing cholangitis (ASC), and de novo AIH after liver transplantation. AIH is an idiopathic disease characterized by immune-mediated hepatocyte injury associated with the destruction of liver cells, causing inflammation, liver failure, and fibrosis, typically associated with autoantibodies. The etiology of AIH is not entirely unraveled, but evidence supports an intricate interaction among genetic variants, environmental factors, and epigenetic modifications. The pathogenesis of AIH comprises the interaction between specific genetic traits and molecular mimicry for disease development, impaired immunoregulatory mechanisms, including CD4+ T cell population and Treg cells, alongside other contributory roles played by CD8+ cytotoxicity and autoantibody production by B cells. These findings delineate an intricate pathway that includes gene to gene and gene to environment interactions with various drugs, viral infections, and the complex microbiome. Epigenetics emphasizes gene expression through hereditary and reversible modifications of the chromatin architecture without interfering with the DNA sequence. These alterations comprise DNA methylation, histone transformations, and non-coding small (miRNA) and long (lncRNA) RNA transcriptions. The current first-line therapy comprises prednisolone plus azathioprine to induce clinical and biochemical remission. Further understanding of the cellular and molecular mechanisms encountered in AIH may depict their impact on clinical aspects, detect biomarkers, and guide toward novel, effective, and better-targeted therapies with fewer side effects.

Clinical, immunological, and genetic features in 780 patients with autoimmune lymphoproliferative syndrome (ALPS) and ALPS-like diseases: A systematic review

BACKGROUND

Autoimmune lymphoproliferative syndrome (ALPS) is a group of genetic disorders characterized by early-onset lymphoproliferation, autoimmune cytopenias, and susceptibility to lymphoma. The majority of ALPS patients carry heterozygous germline mutations in the TNFRSF6 gene. In this study, we conducted a systematic review of patients with ALPS and ALPS-like syndrome.

METHODS

The literature search was performed in Web of Science, Scopus, and PubMed databases to find eligible studies. Additionally, the reference list of all included papers was hand-searched for additional studies. Demographic, clinical, immunological, and molecular data were extracted and compared between the ALPS and ALPS-like syndrome.

RESULTS

Totally, 720 patients with ALPS (532 genetically determined and 189 genetically undetermined ALPS) and 59 cases with ALPS-like phenotype due to mutations in genes other than ALPS genes were assessed. In both ALPS and ALPS-like patients, splenomegaly was the most common clinical presentation followed by autoimmune cytopenias and lymphadenopathy. Among other clinical manifestations, respiratory tract infections were significantly higher in ALPS-like patients than ALPS. The immunological analysis showed a lower serum level of IgA, IgG, and lymphocyte count in ALPS-like patients compared to ALPS. Most (85%) of the ALPS and ALPS-like cases with determined genetic defects carry mutations in the FAS gene. About one-third of patients received immunosuppressive therapy with conventional or targeted immunotherapy agents. A small fraction of patients (3.3%) received hematopoietic stem cell transplantation with successful engraftment, and all except two patients survived after transplantation.

CONCLUSION

Our results showed that the FAS gene with 85% frequency is the main etiological cause of genetically diagnosed patients with ALPS phenotype; therefore, the genetic defect of the majority of suspected ALPS patients could be confirmed by mutation analysis of FAS gene.

Genetic aspects of adult and pediatric autoimmune hepatitis: A concise review

Autoimmune Hepatitis (AIH) is a heterogenous, mostly chronic liver disease that affects people of all age groups, women more often than men. The aim of therapy is to prevent cirrhosis, as it mainly accounts for liver-related mortality in patients with AIH. Rates of remission are high in patients with AIH, but life-long immunosuppressive therapy is required. AIH is hypothesized to originate from immunologic reactivity targeted against mostly unknown self-antigens, potentially triggered by viral infections among other factors. While AIH does not follow a Mendelian inheritance pattern, part of the risk of developing AIH or worse disease course, is attributed to specific genetic risk factors. Major associations for the risk of development of AIH were found for HLA-DRB1*03:01 and HLA-DRB1*04:01 in adult AIH in the only genome-wide association study on AIH. However, other potential risk loci in SH2B3, CARD10 and KIR genes were described. This review covers the current knowledge on genetic risk factors in adult and pediatric AIH.

Neonatal Autoimmune Lymphoproliferative Syndrome: A Case Report and A Brief Review

The authors are reporting a case of autoimmune lymphoproliferative syndrome in a newborn who presented with massive hepatosplenomegaly, thrombocytopenia, and anemia at birth. Antenatal ultrasound revealed a fetus with hepatosplenomegaly. The infant was treated with steroids and sirolimus and is doing well at 4 years of age. This is the first case report of autoimmune lymphoproliferative syndrome presenting as hepatosplenomegaly during fetal life.

Autoimmune Lymphoproliferative Syndrome: An Overview

Autoimmune lymphoproliferative syndrome (ALPS) is an inherited nonmalignant lymphoproliferative disorder characterized by heterozygous mutations within the first apoptosis signal receptor (FAS) signaling pathway. Defects in FAS-mediated apoptosis cause an expansion and accumulation of autoreactive CD4- and CD8- (double-negative) T cells, leading to cytopenias, splenomegaly, lymphadenopathy, autoimmune disorders, and a greatly increased lifetime risk of lymphoma. The differential diagnosis of ALPS includes infection, other inherited immunodeficiency disorders, primary and secondary autoimmune syndromes, and lymphoma. The most consistent pathologic feature is a florid paracortical expansion of double-negative T cells in lymph nodes. A presumptive clinical diagnosis can be made from symptoms and a constellation of laboratory test results. However, a definitive diagnosis requires ancillary testing and enables disease subclassification. Recognition of ALPS is critical, as treatment with immunosuppressive therapies can effectively reduce or ameliorate symptoms for most patients.

Cellular and Molecular Mechanisms of Autoimmune Hepatitis

Autoimmune hepatitis is an uncommon idiopathic syndrome of immune-mediated destruction of hepatocytes, typically associated with autoantibodies. The disease etiology is incompletely understood but includes a clear association with human leukocyte antigen (HLA) variants and other non-HLA gene variants, female sex, and the environment. Pathologically, there is a CD4+ T cell-rich lymphocytic inflammatory infiltrate with variable hepatocyte necrosis and subsequent hepatic fibrosis. Attempts to understand pathogenesis are informed by several monogenetic syndromes that may include autoimmune liver injury, by several drug and environmental agents that have been identified as triggers in a minority of cases, by human studies that point toward a central role for CD4+ effector and regulatory T cells, and by animal models of the disease. Nonspecific immunosuppression is the current standard therapy. Further understanding of the disease's cellular and molecular mechanisms may assist in the design of better-targeted therapies, aid the limitation of adverse effects from therapy, and inform individualized risk assessment and prognostication.

Epigenetics, autoimmunity and hematologic malignancies: a comprehensive review

The relationships between immunological dysfunction, loss of tolerance and hematologic malignancies have been a focus of attention in attempts to understand the appearance of a higher degree of autoimmune disease and lymphoma in children with congenital immunodeficiency. Although multiple hypotheses have been offered, it is clear that stochastic processes play an important role in the immunopathology of these issues. In particular, accumulating evidence is defining a role of epigenetic mechanisms as being critical in this continuous spectrum between autoimmunity and lymphoma. In this review, we focus attention predominantly on the relationships between T helper 17 (Th17) and T regulatory populations that alter local microenvironments and ultimately the expression or transcription factors involved in cell activation and differentiation. Abnormal expression in any of the molecules involved in Th17 and/or Treg development alter immune homeostasis and in genetically susceptible hosts may lead to the appearance of autoimmunity and/or lymphoma. These observations have clinical significance in explaining the discordance of autoimmunity in identical twins. They are also particularly important in the relationships between primary immune deficiency syndromes, immune dysregulation and an increased risk of lymphoma. Indeed, defining the factors that determine epigenetic alterations and their relationships to immune homeostasis will be a challenge greater or even equal to the human genome project.

Precise mapping of the CD95 pre-ligand assembly domain

Pre-association of CD95 at the plasma membrane is mandatory for efficient death receptor signaling. This homotrimerization occurs through self-association of an extracellular domain called the pre-ligand assembly domain (PLAD). Using novel molecular and cellular tools, we confirmed that CD95-PLAD is necessary to promote CD95 multimerization and plays a pivotal role in the transmission of apoptotic signals. However, while a human CD95 mutant deleted of the previously described PLAD domain (amino acids 1 to 66) fails to interact with its wild-type counterpart and trigger autonomous cell death, deletion of amino acids 1 to 42 does not prevent homo- or hetero (human/mouse)-oligomerization of CD95, and thus does not alter transmission of the apoptotic signal. Overall, these findings indicate that the region between amino acids 43 to 66 corresponds to the minimal motif involved in CD95 homotypic interaction and is necessary to convey an efficient apoptotic signal. Interfering with this PLAD may represent a new therapeutic strategy for altering CD95-induced apoptotic and non-apoptotic signals.

CD95-mediated cell signaling in cancer: mutations and post-translational modulations

Apoptosis has emerged as a fundamental process important in tissue homeostasis, immune response, and during development. CD95 (also known as Fas), a member of the tumor necrosis factor receptor (TNF-R) superfamily, has been initially cloned as a death receptor. Its cognate ligand, CD95L, is mainly found at the plasma membrane of activated T-lymphocytes and natural killer cells where it contributes to the elimination of transformed and infected cells. According to its implication in the immune homeostasis and immune surveillance, and since several malignant cells of various histological origins exhibit loss-of-function mutations, which cause resistance towards the CD95-mediated apoptotic signal, CD95 has been classified as a tumor suppressor gene. Nevertheless, this assumption has been recently challenged, as in certain pathophysiological contexts, CD95 engagement transmits non-apoptotic signals that promote inflammation, carcinogenesis or liver/peripheral nerve regeneration. The focus of this review is to discuss these apparent contradictions of the known function(s) of CD95.

How I treat autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) represents a failure of apoptotic mechanisms to maintain lymphocyte homeostasis, permitting accumulation of lymphoid mass and persistence of autoreactive cells that often manifest in childhood with chronic nonmalignant lymphadenopathy, hepatosplenomegaly, and recurring multilineage cytopenias. Cytopenias in these patients can be the result of splenic sequestration as well as autoimmune complications manifesting as autoimmune hemolytic anemia, immune-mediated thrombocytopenia, and autoimmune neutropenia. More than 300 families with hereditary ALPS have now been described; nearly 500 patients from these families have been studied and followed worldwide over the last 20 years by our colleagues and ourselves. Some of these patients with FAS mutations affecting the intracellular portion of the FAS protein also have an increased risk of B-cell lymphoma. The best approaches to diagnosis, follow-up, and management of ALPS, its associated cytopenias, and other complications resulting from infiltrative lymphoproliferation and autoimmunity are presented.

The tumour necrosis factor/TNF receptor superfamily: therapeutic targets in autoimmune diseases

Autoimmune diseases are characterized by the body's ability to mount immune attacks on self. This results from recognition of self-proteins and leads to organ damage due to increased production of pathogenic inflammatory molecules and autoantibodies. Over the years, several new potential therapeutic targets have been identified in autoimmune diseases, notable among which are members of the tumour necrosis factor (TNF) superfamily. Here, we review the evidence that certain key members of this superfamily can augment/suppress autoimmune diseases.

Analysis of single nucleotide polymorphisms in the FAS and CTLA-4 genes of peripheral T-cell lymphomas

Angioimmunoblastic T-cell lymphoma (AILT) represents a subset of T-cell lymphomas but resembles an autoimmune disease in many of its clinical aspects. Despite the phenotype of effector T-cells and high expression of FAS and CTLA-4 receptor molecules, tumor cells fail to undergo apoptosis. We investigated single nucleotide polymorphisms (SNPs) of the FAS and CTLA-4 genes in 94 peripheral T-cell lymphomas. Although allelic frequencies of some FAS SNPs were enriched in AILT cases, none of these occurred at a different frequency compared to healthy individuals. Therefore, SNPs in these genes are not associated with the apoptotic defect and autoimmune phenomena in AILT.

Modulation of apoptosis as a target for liver disease

Apoptosis mediated via extrinsic or intrinsic pathways is essential for maintaining cellular homeostasis in the liver. The extrinsic pathway is triggered from the cell surface by engagement of death receptors as CD95, TRAIL (TNF-related apoptosis inducing ligand) and TNF (tumour necrosis factor) or TGF-beta (transforming growth factor beta) receptors. The intrinsic pathway is initiated from the mitochondria and can be influenced by Bcl-2 family members. Both pathways are intertwined and play a physiological role in the liver. Dysregulation of apoptosis pathways contributes to diseases as hepatocellular carcinoma, viral hepatitis, autoimmune hepatitis, ischaemia-reperfusion injury, iron or copper deposition disorders, toxic liver damage and acute liver failure. The apoptosis defects are often central pathogenetic events; hence molecular mechanisms of apoptosis give not only insight into disease mechanisms but also provide potential corresponding therapeutic candidates in liver disease. The focus of this review is the identification of apoptotic signalling components in the liver as therapeutic targets.

Autoimmune lymphoproliferative syndrome: molecular basis of disease and clinical phenotype

Autoimmune lymphoproliferative syndrome (ALPS) is a variable clinical condition manifest by lymphoproliferative disease, autoimmune cytopenias and susceptibility to malignancy. Central to the cellular pathogenesis is defective FAS-induced apoptosis, which in turn leads to dysregulation of lymphocyte homeostasis. The majority of patients have heterozygous mutations in the FAS (TNFRSF6) gene, but the condition is genetically heterogeneous and mutations in FAS ligand and caspase-8 and caspase-10, all of which are involved in Fas mediated signalling, have also been identified. This review provides a detailed insight into the pathophysiology of lymphocyte apoptosis and how this relates to the variable and complex clinical manifestations of ALPS.

Single nucleotide polymorphisms in the apoptosis receptor gene TNFRSF6

The homotrimeric Fas receptor, an inducer of lymphocyte apoptosis, plays a critical role in cellular pathways of immune homeostasis and immunologic tolerance. Inherited and acquired defects in the Fas gene, TNFRSF6 (tumor necrosis factor receptor superfamily member 6) have been associated with human autoimmune lymphoproliferative syndrome (ALPS) and a spectrum of other complex autoimmune diseases and malignancies. In addition to over 60 deleterious mutations associated with dominant inhibitory defects or null mutations of TNFRSF6, several sequence variants have been noted. To facilitate interpretation of genotypes of this important locus, we sequenced DNA from unrelated, healthy Caucasians and African Americans. Two new and 12 previously recorded SNPs were confirmed, and their allele frequencies were determined. We also investigated haplotype frequencies and linkage disequilibrium (LD) coefficients for these SNPs in Caucasians. Four TNFRSF6 SNP pairs were found to be in strong LD. The TNRFSF6 SNPs are useful for linkage and loss of heterozygosity studies probing the role of Fas-mediated apoptosis in autoimmune diseases and malignancies.

Detection of autoimmune regulator gene mutations in children with type 2 autoimmune hepatitis and extrahepatic immune-mediated diseases

Autoimmune regulator gene mutations were identified in 3 children with type 2 autoimmune hepatitis and extrahepatic immune diseases, including 1 child with immune hepatitis recurrence after liver transplantation. These findings suggest that autoimmune regulator gene variants might predispose children to systemic autoimmune disease, a recurrence of immune disease, or both.

Autoimmune lymphoproliferative syndrome

PURPOSE OF REVIEW

The autoimmune lymphoproliferative syndrome is a recently identified human disorder of lymphocyte apoptosis that has provided important information about Fas-mediated lymphocyte apoptosis. In this review we summarize current information regarding the diagnosis, management and underlying molecular basis of the syndrome.

RECENT FINDINGS

The genetic basis of autoimmune lymphoproliferative syndrome has continued to expand with the recently identified defects in caspase-8 and caspase-10 along with the more frequent defect in Fas and unusual Fas ligand deficiency. Genotype-phenotype links and differences continue to be assessed while the variation in penetrance remains to be fully defined. An increased risk for lymphoreticular malignancy has clearly been established in those autoimmune lymphoproliferative syndrome patients with defects in the gene encoding for the death domain of Fas. Therapy remains directed at managing acute problems although a preliminary report suggests sulphadoxine-pyrimethamine treatment may be successful in patients with the syndrome or autoimmune lymphoproliferative syndrome-like disease and this approach is presently being studied in a controlled trial.

SUMMARY

Defects in multiple molecules within the Fas apoptotic pathway may result in autoimmune lymphoproliferative syndrome and, despite recent advances, a number of patients remain with unidentified genetic defects. There is also clear need for improved understanding of mechanisms underlying the development of autoimmunity in this disorder and to provide early evidence for development of malignancy. This syndrome is the first human disorder linked to a germline defect in lymphocyte apoptosis and it continues to be an area of productive research and new information regarding this process of lymphocyte homeostasis and its role in human disease.

Function and regulation of the CD95 (APO-1/Fas) ligand in the immune system

CD95/CD95L mediated apoptosis is an important mechanism of immune homeostasis. It is instrumental for termination of an immune response and mainly be involved in peripheral tolerance. Dysregulation of the CD95/CD95L system leads to severe diseases. In this review, we present a survey of the role of the CD95/CD95L system in the immune system and, particularly, focus on the signals and transcription factors (NF-AT, Egr, NF-kappaB, AP-1, c-Myc, Nur77, IRFs, SP-1, ALG-4, ROR(gamma)t, and CIITA) involved in CD95L expression. It should also be evident from this review that a profound insight into the molecular mechanisms of CD95L activation should allow to explore potential therapeutic means to treat CD95/CD95L-dependent diseases.

Autoimmune lymphoproliferative syndrome: etiology, diagnosis, and management

Autoimmune lymphoproliferative syndrome (ALPS) is a childhood disorder characterized by chronic, nonmalignant lymphoproliferation and autoimmunity, most commonly involving cells of hematopoietic origin. Mutations of the tumor necrosis factor receptor super family member 6 (TNFRSF6) gene, coding for the apoptosis-inducing protein Fas (Apo-1, CD95) are involved in the physiopathology of the syndrome, although the complete mechanism by which the syndrome is caused has not yet been unraveled. Although the syndrome has a benign nature, life-threatening complications can demand treatment. Treatment schedules, including corticosteroids, low doses of chemotherapy, granulocyte colony stimulating factor, or splenectomy, have varying results. Treatment with the antimalarial drug pyrimethamine/sulfadoxine (25/500mg per tablet) seems to be a new, well tolerated, and efficient approach, although larger studies will have to demonstrate the true value of this drug in patients with ALPS.

Cell-death signaling and human disease

The autoimmune lymphoproliferative syndrome (ALPS) in humans and the lpr mouse strain are the first examples of primary apoptosis defects caused by inherited death-receptor mutations. They illustrate the role of Fas and Fas ligand in the control of autoimmune T-cell and B-cell proliferation. Subsequent analyses of ALPS in humans have highlighted the role of caspase 10 in the induction of apoptosis. The recent identification of a human caspase 8 defect has revealed a potential connection between apoptosis pathways and immune-receptor signaling. The genetic basis of ALPS is extremely complex, as multiple factors are potentially involved in the pathogenesis of this disease, thus offering an interesting model with which to unravel the mechanisms involved in T-cell homeostasis and self-tolerance.

Autoimmune lymphoproliferative syndromes: genetic defects of apoptosis pathways

Human and mouse natural mutants presenting with lymphoproliferative syndrome and autoimmunity (ALPS) have enlightened the role of the Fas and FasL in lymphocyte cell death and peripheral tolerance. Further study of the genetic basis of the human pathology led to the identification of apoptosis signaling defect, and pointed out to the crucial role of caspase-10 in the process of apoptosis induction. In contrast, the absence of lymproliferation in engineered mutants of 'death pathways' suggests that additional events are necessary to recapitulate the overt phenotype of ALPS patients or MRL/lpr mice. Moreover, these models highlight the roles of Fas and associated molecules, such as FADD and caspase-8, in lymphocyte development or activation. This review will discuss the main findings provided by the study of mouse models and human conditions.

The conformational alteration of the mutated extracellular domain of Fas in an adult T cell leukemia cell line

Fas (APO-1/CD95) is a cell surface receptor involved in apoptosis. Almost all adult T cell leukemia (ATL) cells express abundant Fas antigen and show apoptosis induced by IgM anti-Fas monoclonal antibody (mAb). We established the ATL cell line, RSO4, which was obtained from Fas-sensitive ATL cell line SO4 and showed resistance to apoptosis induced by the mAb. By sequencing analysis of Fas gene, we found the mutation with the transition of A-G at nucleotide 373 at exon 2 among the extracellular domain (ECD), resulting in substitution of arginine for histidine. The molecular modeling suggested the definitive conformational alteration around residues 52-58 among the cysteine-rich domain (CRD) 1. It was suggested that the polymerization of Fas antigen, which was the essential process for the efficient induction of apoptosis, was interfered by the alteration of CRD1, and that this portion, named the "histidine-rich region," played a critical role in Fas assembly.

Inhibition of intracellular peroxides and apoptosis of lymphocytes in lupus-prone B/W mice by dietary n-6 and n-3 lipids with calorie restriction

Our earlier studies have shown that calorie restriction and n-3 fatty acids inhibit autoimmune disease and prolong life span. Experiments were designed to study the alteration of apoptosis and its mediators in B/W mice fed either n-6 fatty acids [5% corn oil (CO)] or n-3 fatty acids [5% fish oil (FO)] and either allowed access to the diet ad libitum (AL) or restricted in caloric intake by 40% (CR), from 4 weeks of age. At 4 months (young) and 9 months (old) mice were killed, splenic lymphocytes were isolated, and apoptosis was measured with Annexin V and PI staining. Apoptosis was decreased in splenic lymphocytes from both young and old CR mice compared to their respective AL-fed control groups regardless of fat source. Increasing apoptosis with age was observed in CO/AL, CO/CR, and FO/AL mice which correlated closely with significantly higher cellular peroxides measured by flow cytometry using dichlorofluourescein diacetate (DCFH-DA), whereas in both CO/CR and FO/CR peroxide levels remained low in old mice. Furthermore, CR increased the proliferative response of splenic lymphocytes and decreased the Fas (CD95) and Fas-L protein expression in CD4+ lymphocytes from old mice. Higher levels of Fas and Fas-L expression were observed in old mice compared to young mice. Bcl-2 levels were elevated in both young and old CR groups compared to the respective AL groups. Calorie restriction prevented the loss of CD8 cells in old mice fed both the CO and the FO diet. In summary, CR resulted in decreased apoptosis accompanied by alterations in Fas, Fas-L, and Bcl-2 expression in old mice, increased life span, and delayed onset of kidney disease.

Soluble Fas gene therapy protects against Fas-mediated apoptosis of hepatocytes but not the lethal effects of Fas-induced TNF-alpha production by Kupffer cells

The elevation of soluble Fas (sFas) in the sera of patients with liver disease suggests a role for sFas in the disease process; whether it is protective or not is controversial. To determine the effects of sFas on Fas-induced liver apoptosis, we manipulated mice to produce sFas by transfecting them in vivo with different amounts of an adenovirus that produces mouse sFas driven by the CMV promoter (AdsFas). Fas-mediated apoptosis was induced by administration of anti-mouse Fas (Jo2; 10 microg/mouse) one week later. The administration of AdsFas (10(3), 10(7), or 10(9) pfu/mouse), which was associated with only minimal side-effects, resulted in a significant reduction in the liver transaminase levels and mortality of the mice on challenge with Jo2, as compared to control mice treated with AdLacZ. However, the protective effect of AdsFas was not complete. The possibility that Jo2-induction of TNF-alpha in the Kupffer cells of the liver contributes to the pathology was therefore tested. Although administration of soluble TNF receptor (sTNFRI) alone did not protect the mice from the lethal effects of Jo2, administration of sTNFRI (200 microg/mouse) after infection with AdsFas (10(9) pfu/mouse) resulted in 100% survival of the mice on challenge with Jo2. To confirm that the production of TNF-alpha by Kupffer cells produce the lethal effects of Jo2 that remained after treatment with AdsFas, these cells were selectively ablated by treatment of the mice with gadolinium chloride prior to challenge with Jo2. This treatment greatly reduced early mortality and hepatocellular damage as well as TNF-alpha production 6 h after injection of Jo2. These results indicate that: (1) AdsFas prevents Jo2-induced apoptosis of hepatocytes; (2) In addition to mediating Fas-mediated apoptosis of hepatocytes, Jo2 can separately induce TNF-alpha production by Kupffer cells resulting in early mortality, and (3) Optimal protection from Jo2-induced mortality can be achieved by protection of liver cells by pretreatment with both AdsFas and sTNFRI.

Autoimmune lymphoproliferative syndrome type III, an indefinite disorder

Autoimmune Lymphoproliferative Syndrome (ALPS) is a childhood disorder characterized by chronic nonmalignant lymphoproliferation and autoimmunity. Although the pathogenesis is not fully understood, deficient Fas mediated apoptosis appears to be an important factor. This deficiency can be caused by a mutation of the APTI gene (ALPS type Ia), of the FasL gene (ALPS type Ib), or of the Caspase-10 gene (ALPS type II). In one sub population of patients, no mutations have been identified as yet (ALPS type III). According to published data, the latter group is much smaller than the group of patients with ALPS type Ia. However, because of the variability of the clinical presentation and the absence of a known genetic defect, this disease is difficult to diagnose, the more so as few data have been reported on these patients. Thus, ALPS type III could be more common than believed until now. In this review we provide evidence for this hypothesis.

Autoimmune lymphoproliferative syndrome type III: an indefinite disorder

Autoimmune Lymphoproliferative Syndrome (ALPS) is a childhood disorder characterized by chronic nonmalignant lymphoproliferation and autoimmunity. Although the pathogenesis is not fully understood, deficient Fas mediated apoptosis appears to be an important factor. This deficiency can be caused by a mutation of the APT1 gene (ALPS type Ia), of the FasL gene (ALPS type Ib), or of the Caspase-10 gene (ALPS type II). In one sub population of patients, no mutations have been identified as yet (ALPS type III). According to published data, the latter group is much smaller than the group of patients with ALPS type Ia. However, because of the variability of the clinical presentation and the absence of a known genetic defect, this disease is difficult to diagnose, the more so as few data have been reported on these patients. Thus, ALPS type III could be more common than believed until now. In this review we provide evidence for this hypothesis.

Autoimmune lymphoproliferative syndrome. A human disorder of abnormal lymphocyte survival

The importance of Fas in the homeostatic balance between lymphocyte survival and death is underscored by the three main consequences of defective Fas-mediated apoptosis, as experienced by patients with ALPS: (1) abnormal accumulation of lymphocytes results in lymphadenopathy, hepatosplenomegaly, and hypersplenism; (2) failure of removal of potentially autoreactive lymphocytes, a process normally used to eliminate lymphocytes that have escaped negative selection in the thymus and bone marrow (see article by Fleisher and Blessing, p. 1197), is associated with the appearance of autoimmune manifestations; and (3) inappropriate survival of lymphocytes may lead to the development of malignancies. As with other "experiments of nature," the many aspects of ALPS have provided valuable new insights into the immune system and the importance of a proper balance between life and death of lymphocytes. ALPS is an example of how a mouse disease model was applied directly to the identification of the molecular basis and the understanding of a remarkable disease in humans. It is also an example of clinical observations being linked to basic scientific data to unlock the underlying defect(s) causing a disease. Despite the difficulty in fully understanding the complex nature of the clinical course, the immunologic abnormalities, and the genetic aspects of ALPS, the accumulated experience in diagnosis, treatment, and follow-up of patients and relatives has generated a "road map" that can be used as a guide for their care. As examples, the appreciation that manifestations of lymphoproliferation usually subside over time has allowed a "wait-and-see" approach in many patients who might previously have been treated aggressively. The appreciation that these patients are at increased risk for malignancies has mandated the adoption of careful and lifelong follow-up. Future efforts directed at careful clinical follow-up and scientific investigation are required to learn more about the incidence and natural history of ALPS, therapeutic interventions directed at altering the consequences of TNFRSF6 mutations, and the identification of other genetic and environmental factors that may have a role in the pathogenesis of ALPS.

Clustering of distinct autoimmune diseases associated with functional abnormalities of T cell survival in children

To ascertain whether alterations of lymphocyte switching off may be associated with clustering of autoimmune diseases in children, Fas- and C2-ceramide-induced cell death was evaluated on T cell lines derived from three patients affected by clustering of autoimmune disorders. Three patterns were found: patient 3 was resistant to Fas- and C2-ceramide, patient 1 was resistant to Fas, but sensitive to C2-ceramide, patient 2 was resistant to C2-ceramide, but sensitive to Fas. By contrast, Fas- and C2-ceramide-induced cell death was normal in five children with systemic juvenile rheumatoid arthritis, five children with insulin-dependent diabetes and 10 age-matched healthy controls. Surface expression of Fas was low in patient 1, but normal in patients 2 and 3. Together with normal Fas transcripts, patients 2 and 3 displayed a transcript 152 bp longer than the normal one retaining intron 5. Our data indicate that polyreactive autoimmune syndromes may be associated with heterogeneous alteration of the immune response switching-off system.

Deficiency of the Fas apoptosis pathway without Fas gene mutations is a familial trait predisposing to development of autoimmune diseases and cancer

Fas/Apo-1 (CD95) triggers programmed cell death (PCD) and is involved in immune response control and cell-mediated cytotoxicity. In the autoimmune/lymphoproliferative syndrome (ALPS), inherited loss-of-function mutations of the Fas gene cause nonmalignant lymphoproliferation and autoimmunity. We have recently identified an ALPS-like clinical pattern (named autoimmune lymphoproliferative disease [ALD]) in patients with decreased Fas function, but noFas gene mutation. They also displayed decreased PCD response to ceramide, triggering a death pathway partially overlapping that used by Fas, which suggests that ALD is caused by downstream alterations of the Fas signaling pathway. Decreased Fas function is also involved in tumor development, because somatic mutations hitting the Fas system may protect neoplastic cells from immune surveillance. This work assessed the inherited component of the ALD defect by evaluating Fas- and ceramide-induced T-cell death in both parents and 4 close relatives of 10 unrelated patients with ALD. Most of them (22 of 24) displayed defective Fas- or ceramide-induced (or both) cell death. Moreover, analysis of the family histories showed that frequencies of autoimmunity and cancer were significantly increased in the paternal and maternal line, respectively. Defective Fas- or ceramide-induced T-cell death was also detected in 9 of 17 autoimmune patients from 7 families displaying more than a single case of autoimmunity within first- or second-degree relatives (multiple autoimmune syndrome [MAS] patients). Autoimmune diseases displayed by ALD and MAS families included several organ-specific and systemic forms. These data suggest that ALD is due to accumulation of several defects in the same subject and that these defects predispose to development of cancer or autoimmune diseases other than ALPS/ALD.

Deficiency of the Fas apoptosis pathway without Fas gene mutations is a familial trait predisposing to development of autoimmune diseases and cancer

Fas/Apo-1 (CD95) triggers programmed cell death (PCD) and is involved in immune response control and cell-mediated cytotoxicity. In the autoimmune/lymphoproliferative syndrome (ALPS), inherited loss-of-function mutations of the Fas gene cause nonmalignant lymphoproliferation and autoimmunity. We have recently identified an ALPS-like clinical pattern (named autoimmune lymphoproliferative disease [ALD]) in patients with decreased Fas function, but noFas gene mutation. They also displayed decreased PCD response to ceramide, triggering a death pathway partially overlapping that used by Fas, which suggests that ALD is caused by downstream alterations of the Fas signaling pathway. Decreased Fas function is also involved in tumor development, because somatic mutations hitting the Fas system may protect neoplastic cells from immune surveillance. This work assessed the inherited component of the ALD defect by evaluating Fas- and ceramide-induced T-cell death in both parents and 4 close relatives of 10 unrelated patients with ALD. Most of them (22 of 24) displayed defective Fas- or ceramide-induced (or both) cell death. Moreover, analysis of the family histories showed that frequencies of autoimmunity and cancer were significantly increased in the paternal and maternal line, respectively. Defective Fas- or ceramide-induced T-cell death was also detected in 9 of 17 autoimmune patients from 7 families displaying more than a single case of autoimmunity within first- or second-degree relatives (multiple autoimmune syndrome [MAS] patients). Autoimmune diseases displayed by ALD and MAS families included several organ-specific and systemic forms. These data suggest that ALD is due to accumulation of several defects in the same subject and that these defects predispose to development of cancer or autoimmune diseases other than ALPS/ALD.

Autoimmune lymphoproliferative syndrome, a disorder of apoptosis

Autoimmune Lymphoproliferative Syndrome (ALPS) is a recently recognized disease in which a genetic defect in programmed cell death, or apoptosis, leads to breakdown of lymphocyte homeostasis and normal immunologic tolerance. Some authors have referred to ALPS as Canale-Smith syndrome or lymphoproliferative syndrome with autoimmunity. Patients with ALPS have chronic enlargement of the spleen and lymph nodes, various manifestations of autoimmunity, and elevation of a normally rare population of "double negative T cells" (DNTs), T lymphocytes bearing alpha beta T cell receptors and expressing neither cluster differentiation (CD)4 nor CD8 surface antigens. When lymphocytes from patients with ALPS are cultured in vitro, they are resistant to apoptosis as compared to cells from healthy controls. Most patients with ALPS have mutations in a gene now named TNFRSF6 (tumor necrosis factor receptor gene superfamily member 6). This gene, previously known as apoptosis antigen 1 (APT1), encodes the cell surface receptor for the major apoptosis pathway in mature lymphocytes; this receptor has also had many names, including Fas (to be used here), CD95, and APO-1. ALPS is subdivided into: 1) Type Ia, ALPS with mutant Fas; 2) Type Ib, lymphadenopathy and mutation in the ligand for Fas in one patient with systemic lupus erythematosus; 3) Type II, ALPS with mutant caspase 10; and 4) Type III, ALPS as yet without any defined genetic cause.

In Vivo Evidence That Caspase-3 Is Required for Fas-Mediated Apoptosis of Hepatocytes

Caspase-3 is essential for Fas-mediated apoptosis in vitro. We investigated the role of caspase-3 in Fas-mediated cell death in vivo by injecting caspase-3-deficient mice with agonistic anti-Fas Ab. Wild-type controls died rapidly of fulminant hepatitis, whereas the survival of caspase-3−/− mice was increased due to a delay in hepatocyte cell death. Bcl-2 expression in the liver was dramatically decreased in wild-type mice following anti-Fas injection, but was unchanged in caspase-3−/− mice. Hepatocytes from anti-Fas-injected wild-type, but not caspase-3−/−, mice released cytochrome c into the cytoplasm. Western blotting confirmed the lack of caspase-3-mediated cleavage of Bcl-2. Presumably the presence of intact Bcl-2 in caspase-3−/− hepatocytes prevents the release of cytochrome c from the mitochondria, a required step for the mitochondrial death pathway. We also show by Western blot that Bcl-xL, caspase-9, caspase-8, and Bid are processed by caspase-3 in injected wild-type mice but that this processing does not occur in caspase-3−/− mice. This study thus provides novel in vivo evidence that caspase-3, conventionally known for its downstream effector function in apoptosis, also modifies Bcl-2 and other upstream proteins involved in the regulation of Fas-mediated apoptosis.

Expression in transgenic mice of dominant interfering Fas mutations: a model for human autoimmune lymphoproliferative syndrome

Most humans with autoimmune lymphoproliferative syndrome (ALPS) carry heterozygous dominant mutations in one allele of the gene encoding Fas/APO-1/CD95. ALPS patients, like Fas-deficient MRL lpr/lpr mice, have lymphoproliferation, autoimmunity, increased CD4(-)/CD8(-) T lymphocytes, and apoptosis defects. Consistent with the phenotypic variability of lpr/lpr mice of different background strains, human genetic studies indicate that a Fas mutation is insufficient to induce ALPS in all mutation carriers. To investigate the dominant function of human Fas mutations and the additional genetic factor(s) involved in the development of ALPS, we generated transgenic mice expressing, in addition to endogenous Fas, mouse Fas molecules bearing mutations in the intracellular death domain corresponding to mutations identified in ALPS patients. Transgenic mice developed mild features of ALPS, including hepatosplenomegaly, elevated proportions of lymphocytes in spleen and lymph nodes, apoptotic defects, and hepatic lymphocytic infiltrates. Therefore defective murine Fas proteins act in a dominant manner to impair apoptosis of activated lymphocytes and disrupt lymphocyte homeostasis. The influence of genetic background on phenotype was studied by comparing transgenic mice on FVB/N and (FVB/N x MRL) backgrounds with syngenetic control mice and with MRL and MRL lpr/lpr mice. While expression of transgenic mutant Fas contributed mainly to hepatosplenomegaly and accumulation of lymphocytes, MRL background genes played a major role in the production of autoantibodies and elevated serum immunoglobulin levels. Moreover, compared to FVB/N (+/+) mice, a substantial Fas-specific apoptotic defect was found in MRL (+/+) mice, suggesting a mechanism for the known tendency of this strain to develop autoimmunity.

Correlation of increased susceptibility to apoptosis of CD4+ T cells with lymphocyte activation and activity of disease in patients with primary Sjögren's syndrome

OBJECTIVE

To investigate whether a change in the CD95-related apoptosis of T lymphocytes might have a share in the development of the disease in patients with primary Sjögren's syndrome (SS).

METHODS

Two-color cytometric analysis was used to study the phenotype of freshly separated mononuclear cells, while Western blotting was used to detect CD95 ligand (CD95L) expression in total homogenates of isolated CD4+ T lymphocytes. The ability of various subpopulations of T cells to undergo apoptosis was investigated in 1-day cultures in medium alone or following various (anti-CD3, anti-CD95 monoclonal antibody, calcium ionophore) treatments. Apoptosis was detected using 7-aminoactinomycin D dye.

RESULTS

Compared with the findings in healthy controls, the number of CD4+ T lymphocytes was decreased, while their expression of CD95, HLA-DR, and CD45RO was significantly increased in patients with primary SS. A positive correlation was found between the activity of disease, the decrease in the CD4+ T cell number, and the increase in the expression of CD95, CD95L, HLA-DR, and CD45RO molecules within the CD4+ T cell subset. An increased rate of spontaneous, anti-CD3-, or anti-CD95-induced apoptosis was found in the T cells of SS patients, and this was more pronounced in the CD4+ T cell population, correlated with the decreased CD4+ T cell number, increased CD45RO expression, and activity of disease, and concerned mainly the CD95+ cells.

CONCLUSION

These observations indicate that the increased susceptibility to apoptosis of peripheral CD4+ T cells from SS patients correlates with disease activity. These findings support the hypothesis that the chronic activation of the immune system that occurs in this autoimmune disease is the primary mechanism responsible for this cell-deletion process.

Mature T lymphocyte apoptosis--immune regulation in a dynamic and unpredictable antigenic environment

Apoptosis of mature T lymphocytes preserves peripheral homeostasis and tolerance by countering the profound changes in the number and types of T cells stimulated by diverse antigens. T cell apoptosis occurs in at least two major forms: antigen-driven and lymphokine withdrawal. These forms of death are controlled in response to local levels of IL-2 and antigen in a feedback mechanism termed propriocidal regulation. Active antigen-driven death is mediated by the expression of death cytokines such as FasL and TNF. These death cytokines engage specific receptors that assemble caspase-activating protein complexes. These signaling complexes tightly regulate cell death but are vulnerable to inherited defects. Passive lymphokine withdrawal death may result from the cytoplasmic activation of caspases that is regulated by mitochondria and the Bcl-2 protein. The human disease, Autoimmune Lymphoproliferative Syndrome (ALPS) is due to dominant-interfering mutations in the Fas/APO-1/CD95 receptor and other components of the death pathway. The study of ALPS patients reveals the necessity of apoptosis for preventing autoimmunity and allows the genetic investigation of apoptosis in humans. Immunological, cellular, and molecular evidence indicates that throughout the life of a T cell, apoptosis may be evoked in excessive, harmful, or useless clonotypes to preserve a healthy and balanced immune system.

Irradiation-induced up-regulation of Fas in esophageal squamous cell carcinoma is not accompanied by Fas ligand-mediated apoptosis

BACKGROUND AND OBJECTIVES

Fas (APO-1) induces apoptosis after binding Fas ligand (FasL). Evidence suggests that tumors may use this interaction to evade the host immune response. Fas/FasL expression has not been reported in esophageal cancer. We hypothesized that Fas expression would render esophageal cancer cells susceptible to Fas ligation and that irradiation of the cells would increase Fas expression.

METHODS

Two human esophageal squamous cell carcinoma lines, KYSE 150, which has a wild-type (wt) p53 gene, and 410 (mutated p53), were irradiated. Reverse-transcriptase polymerase chain reaction was used to detect Fas and FasL expression. Fas protein was quantitated by enzyme-linked immunosorbent assay and its presence further confirmed by Western analysis. FasL was detected by Western analysis. Cells were treated with Fas monoclonal antibody (maximum 0.05 microg/ml)+/-cycloheximide, and viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cells were also transduced with FasL cDNA and then quantified.

RESULTS

Both lines expressed Fas and FasL, but only the KYSE 150 cell line displayed an increase in Fas following irradiation. No alteration in cell growth was detected for Fas antibody- or FasL-transduced groups versus controls.

CONCLUSIONS

We have demonstrated Fas and FasL expression in esophageal tumor lines. We have also shown that Fas levels are significantly increased in response to irradiation in a wt p53 line. However, cells were resistant to treatment with Fas antibody or following transduction with FasL, suggesting that these tumor cells may use Fas/FasL expression to evade the host immune response.

Perforin-independent CD8(+) T-cell-mediated cytotoxicity of alveolar epithelial cells is preferentially mediated by tumor necrosis factor-alpha: relative insensitivity to Fas ligand

CD8(+) T cells appear to play an important pathophysiologic role in many inflammatory lung diseases. The primary effector function of this T-cell subset is cytolysis of virus-infected cells, and it is widely believed that there are two primary molecular mechanisms by which this occurs: the perforin/granzyme-mediated pathway of cytolysis, and the Fas ligand (FasL)-Fas (CD95/APO-1) pathway of induction of target-cell apoptosis. This conclusion is based primarily on data obtained with hematopoetic cell lines as target cells. There is also a growing body of evidence that Fas is involved in the transduction of apoptotic signals in a variety of inflammatory disease states, particularly involving the liver and the lung. In the study reported here we took advantage of a novel in vitro assay to directly assess the effector mechanisms employed in CD8(+) T-cell-mediated cytolysis of alveolar epithelial cells. We present evidence that FasL-induced, Fas-mediated apoptosis does not directly contribute to T-cell-mediated cytolysis of alveolar epithelial-derived cells, even though Fas is expressed and functional on these cells. We also demonstrated that the perforin-independent cytolytic activity of CD8(+) T cells against alveolar epithelial-derived cells is explained entirely by tumor necrosis factor-alpha (TNF-alpha), which is expressed on CD8(+) T cells. Furthermore, we show that bystander cytolysis of alveolar epithelial-derived cells by antiviral CD8(+) T cells is entirely perforin-independent. This activity is mediated exclusively by TNF-alpha. Both alveolar epithelial-derived cells and primary murine type II cells show susceptibility to apoptosis triggered by soluble TNF-alpha, without the need for transcriptional or translational inhibition. We also confirmed the resistance of alveolar type II cells to FasL in vivo by performing adoptive transfer of perforin-deficient antiviral CD8(+) T cells into transgenic mice expressing a target antigen in type II epithelial cells. Significant lung injury developed in the transgenic CD8(+) T-cell recipients, whether or not Fas was expressed in these animals. Furthermore, preincubation of the T cells with antibody to TNF-alpha completely abolished the injury. These results suggest that alveolar epithelial cells are relatively sensitive to T cell-triggered, TNF-alpha-mediated apoptosis, and resistant to apoptosis triggered by FasL. These observations may have important ramifications for understanding of the pathophysiology of interstitial and inflammatory lung diseases.

Autoimmune lymphoproliferative syndrome with defective Fas: genotype influences penetrance

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of lymphocyte homeostasis and immunological tolerance. Most patients have a heterozygous mutation in the APT1 gene, which encodes Fas (CD95, APO-1), mediator of an apoptotic pathway crucial to lymphocyte homeostasis. Of 17 unique APT1 mutations in unrelated ALPS probands, 12 (71%) occurred in exons 7-9, which encode the intracellular portion of Fas. In vitro, activated lymphocytes from all 17 patients showed apoptotic defects when exposed to an anti-Fas agonist monoclonal antibody. Similar defects were found in a Fas-negative cell line transfected with cDNAs bearing each of the mutations. In cotransfection experiments, Fas constructs with either intra- or extracellular mutations caused dominant inhibition of apoptosis mediated by wild-type Fas. Two missense Fas variants, not restricted to patients with ALPS, were identified. Variant A(-1)T at the Fas signal-sequence cleavage site, which mediates apoptosis less well than wild-type Fas and is partially inhibitory, was present in 13% of African American alleles. Among the ALPS-associated Fas mutants, dominant inhibition of apoptosis was much more pronounced in mutants affecting the intracellular, versus extracellular, portion of the Fas receptor. Mutations causing disruption of the intracellular Fas death domain also showed a higher penetrance of ALPS phenotype features in mutation-bearing relatives. Significant ALPS-related morbidity occurred in 44% of relatives with intracellular mutations, versus 0% of relatives with extracellular mutations. Thus, the location of mutations within APT1 strongly influences the development and the severity of ALPS.

The molecular basis for apoptotic defects in patients with CD95 (Fas/Apo-1) mutations

Heterozygous mutations of the receptor CD95 (Fas/Apo-1) are associated with defective lymphocyte apoptosis and a clinical disease characterized by lymphadenopathy, splenomegaly, and systemic autoimmunity. From our cohort of 11 families, we studied eight patients to define the mechanisms responsible for defective CD95-mediated apoptosis. Mutations in and around the death domain of CD95 had a dominant-negative effect that was explained by interference with the recruitment of the signal adapter protein, FADD, to the death domain. The intracellular domain (ICD) mutations were associated with a highly penetrant Canale-Smith syndrome (CSS) phenotype and an autosomal dominant inheritance pattern. In contrast, mutations affecting the CD95 extracellular domain (ECD) resulted in failure of extracellular expression of the mutant protein or impaired binding to CD95 ligand. They did not have a dominant-negative effect. In each of the families with an ECD mutation, only a single individual was affected. These observations were consistent with differing mechanisms of action and modes of inheritance of ICD and ECD mutations, suggesting that individuals with an ECD mutation may require additional defect(s) for expression of CSS.

Somatic Fas Mutations in Non-Hodgkin’s Lymphoma: Association With Extranodal Disease and Autoimmunity

Fas (APO-1/CD95) is a cell-surface receptor involved in cell death signaling. Germline mutations in the Fas gene have been associated with autoimmune lymphoproliferative syndrome, and somaticFas mutations have been found in multiple myeloma. We have examined the entire coding region and all splice sites of theFas gene in 150 cases of non-Hodgkin’s lymphoma. Overall, mutations were identified in 16 of the tumors (11%). Missense mutations within the death domain of the receptor were associated with retention of the wild-type allele, indicating a dominant-negative mechanism, whereas missense mutations outside the death domain were associated with allelic loss. Fas mutations were identified in 3 (60%) MALT-type lymphomas, 9 (21%) diffuse large B-cell lymphomas, 2 (6%) follicle center cell lymphomas, 1 (50%) anaplastic large cell lymphoma, and 1 unusual case of B-cell chronic lymphocytic leukemia with a marked tropism for skin. Among the 16 patients with somaticFas mutations, 15 showed extranodal disease at presentation, and 6 relapsed in extranodal areas. Ten of 13 evaluable patients showed features suggestive of autoreactive disease. Our data indicate that somatic disruption of Fas may play a role in the pathogenesis of some lymphomas, and suggest a link between Fas mutation, cancer and autoimmunity.

© 1998 by The American Society of Hematology.

Somatic Fas Mutations in Non-Hodgkin’s Lymphoma: Association With Extranodal Disease and Autoimmunity

Fas (APO-1/CD95) is a cell-surface receptor involved in cell death signaling. Germline mutations in the Fas gene have been associated with autoimmune lymphoproliferative syndrome, and somaticFas mutations have been found in multiple myeloma. We have examined the entire coding region and all splice sites of theFas gene in 150 cases of non-Hodgkin’s lymphoma. Overall, mutations were identified in 16 of the tumors (11%). Missense mutations within the death domain of the receptor were associated with retention of the wild-type allele, indicating a dominant-negative mechanism, whereas missense mutations outside the death domain were associated with allelic loss. Fas mutations were identified in 3 (60%) MALT-type lymphomas, 9 (21%) diffuse large B-cell lymphomas, 2 (6%) follicle center cell lymphomas, 1 (50%) anaplastic large cell lymphoma, and 1 unusual case of B-cell chronic lymphocytic leukemia with a marked tropism for skin. Among the 16 patients with somaticFas mutations, 15 showed extranodal disease at presentation, and 6 relapsed in extranodal areas. Ten of 13 evaluable patients showed features suggestive of autoreactive disease. Our data indicate that somatic disruption of Fas may play a role in the pathogenesis of some lymphomas, and suggest a link between Fas mutation, cancer and autoimmunity.

© 1998 by The American Society of Hematology.