Jennifer M. Puck

Dominant interfering fas gene mutations impair apoptosis in a human autoimmune lymphoproliferative syndrome

Five unrelated children are described with a rare autoimmune lymphoproliferative syndrome (ALPS) characterized by massive nonmalignant lymphadenopathy, autoimmune phenomena, and expanded populations of TCR-CD3+CD4-CD8- lymphocytes. These findings, suggesting a genetic defect in the ability of T lymphocytes to respond to normal immunoregulatory mechanisms, prompted an evaluation of lymphocyte apoptosis. Each child had defective Fas-mediated T lymphocyte apoptosis associated with a unique, deleterious Fas gene mutation. One mutation appeared to cause a simple loss of function; however, four others had a dominant negative phenotype when coexpressed with normal Fas. Family studies demonstrated the inheritance of the mutant Fas alleles. The occurrence of Fas mutations together with abnormal T cell apoptosis in ALPS patients suggests an involvement of Fas in this recently recognized disorder of lymphocyte homeostasis and peripheral self-tolerance.

Primary immunodeficiency diseases: an update on the classification from the International Union of Immunological Societies Expert Committee for Primary Immunodeficiency

We report the updated classification of primary immunodeficiencies (PIDs) compiled by the Expert Committee of the International Union of Immunological Societies. In comparison to the previous version, more than 30 new gene defects are reported in this updated version. In addition, we have added a table of acquired defects that are phenocopies of PIDs. For each disorder, the key clinical and laboratory features are provided. This classification is the most up-to-date catalog of all known PIDs and acts as a current reference of the knowledge of these conditions and is an important aid for the molecular diagnosis of patients with these rare diseases.

Primary Immunodeficiency Diseases: an Update on the Classification from the International Union of Immunological Societies Expert Committee for Primary Immunodeficiency 2015

We report the updated classification of primary immunodeficiencies compiled by the Primary Immunodeficiency Expert Committee (PID EC) of the International Union of Immunological Societies (IUIS). In the two years since the previous version, 34 new gene defects are reported in this updated version. For each disorder, the key clinical and laboratory features are provided. In this new version we continue to see the increasing overlap between immunodeficiency, as manifested by infection and/or malignancy, and immune dysregulation, as manifested by auto-inflammation, auto-immunity, and/or allergy. There is also an increased number of genetic defects that lead to susceptibility to specific organisms which reflects the finely tuned nature of immune defense systems. This classification is the most up to date catalogue of all known and published primary immunodeficiencies and acts as a current reference of the knowledge of these conditions and is an important aid for the genetic and molecular diagnosis of patients with these rare diseases.

Inherited Human Caspase 10 Mutations Underlie Defective Lymphocyte and Dendritic Cell Apoptosis in Autoimmune Lymphoproliferative Syndrome Type II

Caspases are cysteine proteases that mediate programmed cell death in phylogenetically diverse multicellular organisms. We report here two kindreds with autoimmune lymphoproliferative syndrome (ALPS) type II, characterized by abnormal lymphocyte and dendritic cell homeostasis and immune regulatory defects, that harbor independent missense mutations in Caspase 10. These encode amino acid substitutions that decrease caspase activity and interfere with death receptor-induced apoptosis, particularly that stimulated by Fas ligand and TRAIL. These results provide evidence that inherited nonlethal caspase abnormalities cause pleiotropic apoptosis defects underlying autoimmunity in ALPS type II.

Hyper-IgE Syndrome with Recurrent Infections — An Autosomal Dominant Multisystem Disorder

BACKGROUND The hyper-IgE syndrome with recurrent infections is a rare immunodeficiency characterized by recurrent skin and pulmonary abscesses and extremely elevated levels of IgE in serum. Associated facial and skeletal features have been recognized, but their frequency is unknown, and the genetic basis of the hyper-IgE syndrome is poorly understood. METHODS We studied 30 patients with the hyper-IgE syndrome and 70 of their relatives. We took histories, reviewed records, performed physical and dental examinations, took anthropometric measurements, and conducted laboratory studies. RESULTS Nonimmunologic features of the hyper-IgE syndrome were present in all patients older than eight years. Seventy-two percent had the previously unrecognized feature of failure or delay of shedding of the primary teeth owing to lack of root resorption. Common findings among patients were recurrent fractures (in 57 percent of patients), hyperextensible joints (in 68 percent), and scoliosis (in 76 percent of patients 16 years of age or older). The classic triad of abscesses, pneumonia, and an elevated IgE level was identified in 77 percent of all patients and in 85 percent of those older than eight. In 6 of 23 adults (26 percent), IgE levels declined over time and came closer to or fell within the normal range. Autosomal dominant transmission of the hyper-IgE syndrome was found, but with variable expressivity. Of the 27 relatives at risk for inheriting the hyper-IgE syndrome, 10 were fully affected, 11 were unaffected, and 6 had combinations of mild immunologic, dental, and skeletal features of the hyper-IgE syndrome. CONCLUSIONS The hyper-IgE syndrome is a multisystem disorder that affects the dentition, the skeleton, connective tissue, and the immune system. It is inherited as a single-locus autosomal dominant trait with variable expressivity.

Pleiotropic defects in lymphocyte activation caused by caspase-8 mutations lead to human immunodeficiency

Apoptosis is a form of programmed cell death that is controlled by aspartate-specific cysteine proteases called caspases. In the immune system, apoptosis counters the proliferation of lymphocytes to achieve a homeostatic balance, which allows potent responses to pathogens but avoids autoimmunity. The CD95 (Fas, Apo-1) receptor triggers lymphocyte apoptosis by recruiting Fas-associated death domain (FADD), caspase-8 and caspase-10 proteins into a death-inducing signalling complex. Heterozygous mutations in CD95, CD95 ligand or caspase-10 underlie most cases of autoimmune lymphoproliferative syndrome (ALPS), a human disorder that is characterized by defective lymphocyte apoptosis, lymphadenopathy, splenomegaly and autoimmunity. Mutations in caspase-8 have not been described in ALPS, and homozygous caspase-8 deficiency causes embryonic lethality in mice. Here we describe a human kindred with an inherited genetic deficiency of caspase-8. Homozygous individuals manifest defective lymphocyte apoptosis and homeostasis but, unlike individuals affected with ALPS, also have defects in their activation of T lymphocytes, B lymphocytes and natural killer cells, which leads to immunodeficiency. Thus, caspase-8 deficiency in humans is compatible with normal development and shows that caspase-8 has a postnatal role in immune activation of naive lymphocytes.

Human severe combined immunodeficiency: Genetic, phenotypic, and functional diversity in one hundred eight infants

OBJECTIVE To determine the relative frequencies of the different genetic forms of severe combined immunodeficiency (SCID) and whether there are distinctive characteristics of the particular genotypes. STUDY DESIGN The demographic, genetic, and immunologic features of 108 infants with SCID who were treated consecutively at Duke University Medical Center were analyzed. RESULTS Eighty-nine subjects were boys and 19 were girls; there were 84 white infants, 16 black infants, and 8 Hispanic infants. Forty-nine had X-linked SCID with mutations of common cytokine receptor gamma chain (gamma c), 16 had adenosine deaminase (ADA) deficiency, 8 had Janus kinase 3 (Jak3) deficiency, 21 had unknown autosomal recessive mutations, 1 had reticular dysgenesis, 1 had cartilage hair hypoplasia, and 12 (all boys) had SCID of undetermined type. Deficiency of ADA caused the most profound lymphopenia; gamma c or Jak3 deficiency resulted in the most B cells and fewest natural killer (NK) cells; NK cells and function were highest in autosomal recessive and unknown types of SCID. CONCLUSIONS Different SCID genotypes are associated with distinctive lymphocyte characteristics. The presence of NK function in ADA-deficient, autosomal recessive, and unknown type SCIDs, and low NK function in a majority of gamma c and Jak3 SCIDs indicates that some molecular lesions affect T, B, and NK cells (gamma c and Jak3), others primarily T cells (ADA deficiency), and others just T and B cells.

Primary immunodeficiencies: 2009 update

More than 50 years after Ogdeon Brutons discovery of congenital agammaglobulinemia, human primary immunodeficiencies (PIDs) continue to unravel novel molecular and cellular mechanisms that govern development and function of the human immune system. This report provides the updated classification of PIDs that has been compiled by the International Union of Immunological Societies Expert Committee on Primary Immunodeficiencies after its biannual meeting in Dublin, Ireland, in June 2009. Since the appearance of the last classification in 2007, novel forms of PID have been discovered, and additional pathophysiology mechanisms that account for PID in human beings have been unraveled. Careful analysis and prompt recognition of these disorders is essential to prompt effective forms of treatment and thus to improve survival and quality of life in patients affected with PIDs.

Genetic Linkage of Hyper-IgE Syndrome to Chromosome 4

The hyper-IgE syndrome (HIES) is a rare primary immunodeficiency characterized by recurrent skin abscesses, pneumonia, and highly elevated levels of serum IgE. HIES is now recognized as a multisystem disorder, with nonimmunologic abnormalities of the dentition, bones, and connective tissue. HIES can be transmitted as an autosomal dominant trait with variable expressivity. Nineteen kindreds with multiple cases of HIES were scored for clinical and laboratory findings and were genotyped with polymorphic markers in a candidate region on human chromosome 4. Linkage analysis showed a maximum two-point LOD score of 3.61 at recombination fraction of 0 with marker D4S428. Multipoint analysis and simulation testing confirmed that the proximal 4q region contains a disease locus for HIES.

An Inherited Disorder of Lymphocyte Apoptosis: The Autoimmune Lymphoproliferative Syndrome

Dr. Stephen Straus (Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases [NIAID], National Institutes of Health [NIH], Bethesda, Maryland): The autoimmune lymphoproliferative syndrome (ALPS) is a recently defined illness that arises in early childhood and can have fatal complications (1-8). It is associated with prominent nonmalignant lymphadenopathy, hepatosplenomegaly, and autoimmune manifestations. Underlying ALPS are heritable mutations in genes that regulate lymphocyte survival by triggering programmed death of lymphocytes, or apoptosis. More important than the mere description of ALPS, however, are the novel insights that this description affords into the mechanisms that regulate lymphocyte homeostasis and contribute to autoimmunity. Historical Perspective Selected features of ALPS have been recognized for decades, but the full-blown syndrome is rare and has only recently been appreciated. Several authors have described families with significant adenopathy and splenomegaly (9-13) and other families with hemolytic anemia, thrombocytopenia, or neutropenia in association with circulating autoantibodies (14-20). Splenomegaly is a feature of autoimmune diseases (such as the Felty syndrome), and moderate lymphadenopathy is seen in up to 70% of patients with lupus (21). The constellation of lymphadenopathy, splenomegaly, and autoimmune cytopenia, however, was described by Canale and Smith in 1967 (22). Weisdorf and Krivit (23) and others (24, 25) noted that similar patients had decreased proportions or function of lymphocyte subsets. Contemporary evaluation of some of these older cases, including a family followed at the NIH, has shown them to be cases of ALPS (4, 13; Straus SE. Unpublished data). Clues to the nature of some of these familial diseases emerged in the early 1990s, when we realized that affected patients resembled mice with the MRL/lpr phenotype; these mice exhibit progressive lymphoproliferation and autoantibody-mediated renal and vascular disease (1, 26, 27). Moreover, the usually rare subset of T cells that show neither the CD4 nor the CD8 co-receptors (CD3+ CD4 CD8 ), or double-negative cells, circulates in increased numbers both in these mice and in our patients. In 1989, Trauth and coworkers (28) reported that a protein called Apo-1 triggered apoptosis of lymphocytes. In 1992, Watanabe-Fukunaga and colleagues (29) found that lpr mice failed to express that same antigen, which they called Fas and, later, CD95. In 1994, the APT1 gene encoding the human homologue of murine Fas was cloned (30). Shortly thereafter, Rieux-Laucat and associates in France (2) and Fisher and colleagues at the NIH (3) demonstrated defective apoptosis and specific Fas mutations in eight children with ALPS. In the ensuing years, more than 40 similar patients have been described (4-8). The autoimmune lymphoproliferative syndrome (sometimes called the Canale-Smith syndrome [4]] represents a failure of apoptotic mechanisms that help maintain normal lymphocyte homeostasis, with a consequent accumulation of lymphoid mass and persistence of autoreactive cells. It is operationally defined as chronic, nonmalignant lymphoproliferation in patients with 1) an elevated percentage [>1%] of double-negative T cells and 2) defective lymphocyte apoptosis that produces a characteristic, if not pathognomic, pathologic picture on microscopic section of the lymph node or spleen (31). Autoimmunity is evident at some point in almost all affected patients. Most cases of ALPS are associated with specific Fas mutations, and yet-undefined mutations in other apoptosis genes are thought to underlie cases in patients with normal Fas. One remarkable case from our clinic shows many features of ALPS (Figure 1). Figure 1. Clinical, radiologic, and histologic features of patients with the autoimmune lymphoproliferative syndrome. A. B. C. D. E. F. G. Case History At age 18 months, NIH ALPS patient 2 was noted to have adenopathy, splenomegaly, and anemia (1, 3, 6). She underwent splenectomy at age 2 years for refractory anemia. Biopsies of splenic tissue, liver, lymph node, and bone marrow were nondiagnostic. Clinical photographs (Figure 1 A) and computed tomographic scans (Figures 1F and 1G) confirmed the presence of persistent, massive enlargement of all lymph node chains and organomegaly. Laboratory studies showed continuing anemia, polyclonal gammopathy, and positive results on a direct Coombs test. Autoimmune manifestations have included glomerulonephritis at age 2 years, idiopathic thrombocytopenic purpura (ITP) at age 9 years, and autoimmune biliary disease since age 10 years. Lymphocyte phenotyping showed absolute increases in B-cell and T-cell counts with a polyclonal expansion of T cells, 25% of which were double negative. The lymph nodes showed lymphoid hyperplasia and plasmacytosis (Figure 1 B), and more than 50% of T cells were double negative (Figures 1C, 1D, and 1E). In vitro studies of peripheral blood mononuclear cells showed defective Fas-mediated apoptosis, and genomic sequencing identified a point mutation in the APT1 gene encoding Fas. Clinical Features and Management Dr. Michael C. Sneller (Laboratory of Immunoregulation, NIAID, NIH): Between 1990 and 1997, the NIH evaluated 45 patients under approved protocols for unexplained chronic lymphadenopathy, splenomegaly, or both. Among these patients, ALPS was subsequently diagnosed in 26 (12 male and 14 female). The remaining patients had some features of ALPS or had entirely different conditions. The Table shows the clinical and salient laboratory features of these 26 patients, of whom 23 had documented Fas mutations. The clinical and laboratory features of ALPS did not differ between patients who had mutations and those who did not. Clinical data on 9 of these patients are reported elsewhere (1, 6). Table. Clinical and Immunologic Features in 26 Patients with the Autoimmune Lymphoproliferative Syndrome Lymphoproliferative Disease All 26 patients initially presented because of lymphadenopathy or splenomegaly at a median age of 11.5 months (range, 1 month to 9 years). Most had both splenomegaly and lymphadenopathy. Splenomegaly was frequently of massive proportions, and hepatomegaly was also common (Figure 1 G). Sixteen patients underwent splenectomy, most often for severe hypersplenism. Lymphadenopathy was massive and distorted normal anatomic landmarks in some patients (Figure 1 A). Enlargement of abdominal and thoracic lymph nodes was frequently seen on computed tomography (Figure 1 F). Regardless of its extent, lymphadenopathy persisted for 2 or more years in almost all patients. Histopathologic analyses of lymph nodes from patients with ALPS show architectural preservation, florid reactive follicular hyperplasia, and marked paracortical expansion with immunoblasts and plasma cells (1, 6, 31) (Figure 1 B). The paracortical expansion may be extensive enough to suggest a diagnosis of immunoblastic lymphoma, with many cells expressing the Ki-67 antigen indicative of active proliferation (32). However, the tissues show no chromosomal abnormalities or evidence of clonality (31). Increased numbers of double-negative T cells are also seen in the paracortical region of lymph node tissue (Figures 1C, 1D, and 1E). This combination of follicular hyperplasia and paracortical expansion by a mixed polyclonal infiltrate containing double-negative T cells differentiates ALPS from other benign and malignant lymphoproliferative lesions. Autoimmunity Circulating autoantibodies, overt autoimmune disease, or both were found in 23 of the 26 patients. Potentially pathogenic autoantibodies were detected in 22 patients (Table) but were not always associated with disease. For example, the direct Coombs test detected antibodies to erythrocytes in 19 patients, but 6 of these patients had no evidence of hemolysis. At least one autoimmune disease was documented in 17 patients (Table) and was evident in 4 of the 17 at the time of initial presentation with lymphoid hyperplasia. In the remaining 13 patients, autoimmune disease developed 6 months to 17 years later, suggesting that the proportion of patients with autoimmune disease increases over time. The most common autoimmune diseases were hemolytic anemia and ITP (Table). Nine patients had at least one episode of hemolysis during which hemoglobin levels decreased to less than 4.4 mmol/L (7 mg/dL). In seven of eight patients with ITP, platelet counts decreased to less than 20 109 cells/L. Five patients also had hemolytic anemia, either concomitantly with active ITP or as isolated episodes with normal platelet counts. Neutropenia (absolute neutrophil count<1.0 106 cells/L) in six patients seemed to result from autoimmune mechanisms because it developed after splenectomy and in the setting of normal myeloid cellularity on bone marrow examination. Several nonhematologic autoimmune diseases also occurred in this group of patients. One patient developed the Guillain-Barr syndrome. Of two patients with glomerulonephritis, one later developed ITP and autoimmune biliary disease (Figure 1 A). Thus, in ALPS, multiple autoimmune diseases involving different organ systems may occur over time in a single patient. No patient developed opportunistic infections or other clinical evidence of immunodeficiency. However, five patients who had splenectomy developed Streptococcus pneumoniae septicemia, usually despite appropriate antibiotic and vaccine prophylaxis. Immunologic Studies The most prominent abnormalities seen with routine immunologic testing of these patients were T-cell and B-cell lymphocytosis, increased numbers of circulating double-negative T lymphocytes, and polyclonal hypergammaglobulinemia. The magnitude of these abnormalities varied (Table). Patients with the most severe lymphoid hyperplasia also had the most pronounced lymphocytosis, the largest numbers of double-negative T lymphocytes, and the highest serum immunoglobulin leve