Immune complexes and the pathogenesis of neutropenia in Felty's syndrome

T-cell Large Granular Lymphocytic Leukemia and Felty Syndrome in Rheumatoid Arthritis: A Case Report

T-cell large granular lymphocytic (LGL) leukemia is characterized by a clonal proliferation of CD3+ T-cells and has been associated with rheumatoid arthritis (RA). Splenomegaly is a common finding and a majority of cases present with cytopenia. Felty syndrome (FS) is characterized by neutropenia and splenomegaly and is also classically described in the literature for its association with RA. Similarities in clinical features, pathogenesis, management, genetics, and immunologic basis of FS and T-cell LGL leukemia have led to the suggestion that they exist on the same spectrum of disease. We present a case of T-cell LGL leukemia in an RA patient with clinical features not distinguishable from features of FS.

Pathogenesis of Extraarticular Manifestations in Rheumatoid Arthritis-A Comprehensive Review

Rheumatoid arthritis (RA) is among the most prevalent and debilitating autoimmune inflammatory chronic diseases. Although it is primarily characterized by destructive peripheral arthritis, it is a systemic disease, and RA-related extraarticular manifestations (EAMs) can affect almost every organ, exhibit a multitude of clinical presentations, and can even be asymptomatic. Importantly, EAMs largely contribute to the quality of life and mortality of RA patients, particularly substantially increased risk of cardiovascular disease (CVD) which is the leading cause of death in RA patients. In spite of known risk factors related to EAM development, a more in-depth understanding of its pathophysiology is lacking. Improved knowledge of EAMs and their comparison to the pathogenesis of arthritis in RA could lead to a better understanding of RA inflammation overall and its initial phases. Taking into account that RA is a disorder that has many faces and that each person experiences it and responds to treatments differently, gaining a better understanding of the connections between the joint and extra-joint manifestations could help to create new treatments and improve the overall approach to the patient.

Persistent Large Granular Lymphocyte Clonal Expansions: “The Root of Many Evils”—And of Some Goodness

Simple Summary

Large granular lymphocyte leukemia (LGLL) is a chronic disorder of either mature T or NK lymphocytes. As clonal expansions of the immune system cells, difficulties in the distinction between a true neoplasia and a physiological reactive process have been common since its description. We review here the different conditions associated with persistent clonal LGL expansions and discuss their potential origin and whether they can modulate the clinical features.

Abstract

Large granular lymphocyte leukemia (LGLL) is a chronic disease of either mature phenotype cytotoxic CD3+ T lymphocytes or CD3- NK cells. LGLL diagnosis is hampered by the fact that reactive persistent clonal LGL expansions may fulfill the current criteria for LGLL diagnoses. In addition to the presence of characteristic clinical and hematological signs such as anemia or neutropenia, LGLL/LGL clonal expansions have been associated with an array of conditions/disorders. We review here the presence of these persistent clonal expansions in autoimmune, hematological disorders and solid neoplasms and after hematopoietic stem cell transplantation. These associations are a unique translational research framework to discern whether these persistently expanded LGL clones are causes or consequences of the concomitant clinical settings and, more importantly, when they should be targeted.

Chronic neutropenia in LGL leukemia and rheumatoid arthritis

This section reviews the diagnostic criteria and pathogenesis of large granular lymphocyte (LGL) leukemia. There is a particular focus on the overlap of LGL leukemia and rheumatoid arthritis (Felty's syndrome). Current understanding of the mechanisms of neutropenia in these disorders is discussed. Finally, treatment indications and therapeutic recommendations are outlined.

Immune-mediated pore-forming pathways induce cellular hypercitrullination and generate citrullinated autoantigens in rheumatoid arthritis

Autoantibodies to citrullinated protein antigens are specific markers of rheumatoid arthritis (RA). Although protein citrullination can be activated by numerous stimuli in cells, it remains unclear which of these produce the prominent citrullinated autoantigens targeted in RA. In these studies, we show that RA synovial fluid cells have an unusual pattern of citrullination with marked citrullination of proteins across the broad range of molecular weights, which we term cellular hypercitrullination. Although histone citrullination is a common event during neutrophil activation and death induced by different pathways including apoptosis, NETosis, and necroptosis/autophagy, hypercitrullination is not induced by these stimuli. However, marked hypercitrullination is induced by two immune-mediated membranolytic pathways, mediated by perforin and the membrane attack complex (MAC), which are active in the RA joint and of importance in RA pathogenesis. We further demonstrate that perforin and MAC activity on neutrophils generate the profile of citrullinated autoantigens characteristic of RA. These data suggest that activation of peptidylarginine deiminases during complement and perforin activity may be at the core of citrullinated autoantigen production in RA. These pathways may be amenable to monitoring and therapeutic modulation.

Diagnosis of Felty's syndrome, distinguished from hematological neoplasm: A case report

Felty’s syndrome (FS) is characterized by the three conditions of rheumatoid arthritis (RA), neutropenia and splenomegaly, and occurs in few cases of longstanding erosive RA. Discriminating between rare occurrences of autoimmune diseases and malignancies is crucial. The present study describes the case of a 17-year-old female with a two-year history of RA, presenting with an irregular fever, hepatosplenomegaly and enlarged lymph nodes. The antinuclear antibody titer was 1:320, while antibody results for anti-dsDNA, anti-Sm and rheumatoid factor were negative. The clinical presentation was similar to that of lymphoma. However, the fluorodeoxyglucose-positron emission tomography and biopsy examinations of the liver and cervical lymph node did not support the diagnosis of lymphoma. According to the laboratory results and clinical symptoms, the differential diagnosis indicated FS, and immunosuppressive agents were administered. Two weeks later, the patient no longer had a fever, and the transaminase levels were normal, associated with shrinkage of the liver and spleen.

Citrullination of autoantigens implicates NETosis in the induction of autoimmunity

Tolerance blocks the expression of autoantibodies, whereas autoimmunity promotes it. How tolerance breaks and autoantibody production begins thus are crucial questions for understanding and treatment of autoimmune diseases. Evidence implicates cell death and autoantigen modifications in the initiation of autoimmune reactions. One form of neutrophil cell death called NETosis deserves attention because it requires the post-translational modification of histones and results in the extracellular release of chromatin. NETosis received its name from NET, the acronym given to Neutrophil Extracellular Trap. The extracellular chromatin incorporates histones in which arginines have been converted to citrullines by peptidylarginine deiminase IV (PAD4). The deiminated chromatin may function to capture or 'trap' bacterial pathogens, thus generating an extracellular complex of deiminated histones and bacterial cell adjuvants. The complex of bacterial antigens and deiminated chromatin may be internalised by host phagocytes during acute inflammatory conditions, as arise during bacterial infections or chronic autoinflammatory disorders. The uptake and processing of deiminated chromatin together with bacterial adjuvants by phagocytes may induce the presentation of modified histone epitopes and co-stimulation, thus yielding a powerful stimulus to break tolerance. Autoantibodies to deiminated histones are prevalent in Felty's syndrome patients and are present in systemic lupus erythematosus (SLE) and patients with rheumatoid arthritis (RA). These observations clearly implicate histone deimination as an epigenetic mark that can act as an autoantibody stimulant.

The spectrum of large granular lymphocyte leukemia and Felty's syndrome

PURPOSE OF REVIEW

Patients with chronic large granular lymphocyte (LGL) leukemia often have rheumatoid arthritis (RA), neutropenia and splenomegaly, thereby resembling the manifestations observed in patients with Felty's syndrome, which is a rare complication of RA characterized by neutropenia and splenomegaly. Both entities have similar clinical and laboratory presentation, as well as a common genetic determinant, HLA-DR4, indicating they may be part of the same disease spectrum. This review paper seeks to discuss the underlying pathogenesis and therapeutic algorithm of RA, neutropenia and splenomegaly in the spectrum of LGL leukemia and Felty's syndrome.

RECENT FINDINGS

We hypothesize that there may be a common pathogenic mechanism between LGL leukemia and typical Felty's syndrome. Phenotypic and functional data have strongly suggested that CD3 LGL leukemia is antigen-activated. Aberrations in the T-cell repertoire with the emergence of oligoclonal/clonal lymphoid populations have been found to play a pivotal role in pathogenesis of RA. The biologic properties of the pivotal T cell involved in RA pathogenesis are remarkably similar to those in leukemic LGL.

SUMMARY

RA-associated T-cell LGL leukemia and articular manifestations of typical Felty's syndrome are not distinguishable. A common pathogenetic link between LGL leukemia and RA is proposed.

Pathogenesis of neutropenia in large granular lymphocyte leukemia and Felty syndrome

T-cell large granular lymphocyte leukemia (TLGL) is an atypical chronic lymphoproliferative disorder derived from cytotoxic T-cells (CTL). Unlike most forms of leukemia, the pattern of bone marrow infiltration in TLGL may be subtle and the cytopenias are often lineage specific, with neutropenia dominating. Both granulocytic survival and proliferation defects are observed and are mediated by humoral and cell-mediated mechanisms respectively. Splenic production of immune complexes induces a neutrophil survival defect, where as Fas expression by leukemic CTL results in a marrow based proliferation defect. These humoral and cell-mediated pathways induce granulocytic apoptosis through independent intracellular mechanisms which are not mutually exclusive and may be observed concurrently in individual patients with either TLGL or FS. A variety of therapeutic interventions have been utilized in the management of TLGL and Felty syndrome, including methotrexate, cyclosporine A, cyclophosphamide, glucocorticoids, myeloid colony stimulating factors and splenectomy. Their efficacy and mechanisms of action are reviewed.

Congenital and Acquired Neutropenia

Our understanding of the pathogenesis of congenital and acquired neutropenia is rapidly evolving. New ground-breaking observations have identified the genes responsible for many of the congenital neutropenia syndromes and are also providing new insights into normal neutrophil commitment and differentiation. Acquired neutropenia remains a poorly understood syndrome, although new insights into its pathogenesis are also emerging, especially with regard to subsets of immune neutropenia.

In Section I, Dr. Marshall Horwitz reviews the current understanding of the genetic basis, molecular pathology, and approaches to treatment of congenital neutropenia and cyclic hematopoiesis. Mutations in the ELA2 gene, which encodes for neutrophil elastase, cause cyclic hematopoiesis. ELA2 mutations are also the most common cause of congenital neutropenia, where their presence may equate with a more severe clinical course and higher frequency of leukemic progression. Emerging evidence indicates interrelatedness with Hermansky Pudlak syndrome and other disorders of neutrophil and platelet granules.

In Section II, Dr. Nancy Berliner presents an overview of the clinical approach to the evaluation and treatment of acquired neutropenia. This includes a review of the pathogenesis of primary and secondary immune neutropenia, drug-induced neutropenia, and non-immune chronic idiopathic neutropenia of adults. Studies used to evaluate patients for potential immune neutropenia are reviewed. Management issues, especially the use of granulocyte colony-stimulating factor (G-CSF), are discussed.

In Section III, Dr. Thomas Loughran, Jr., reviews the pathogenesis and clinical manifestations of large granular lymphocyte (LGL) leukemia. Possible mechanisms of neutropenia are discussed. In particular, discussion focuses on the relationship between LGL leukemia, rheumatoid disease, and Felty’s syndrome, and the complex interplay of defects in neutrophil production, distribution, destruction, and apoptosis that underly the development of neutropenia in those syndromes.

Chronic neutropenia associated with autoimmune disease

Chronic neutropenia with autoimmune diseases is associated mainly with rheumatoid arthritis (RA), as Felty's syndrome or large granular lymphocyte (LGL) leukemia, and with systemic lupus erythematosus (SLE). Recent advances have allowed better understanding regarding the mechanism of neutropenia and improved options for treatment. Target antigens for antineutrophil antibodies have been identified for both Felty's syndrome and for SLE. The role of soluble Fas-ligand (FasL) in inducing apoptosis of neutrophils has been clarified for LGL leukemia and increased neutrophil apoptosis has been described in neutropenic patients with SLE. The role of immune complexes in affecting neutrophil traffic and function continues to be studied. Treatments of neutropenia have included methotrexate, cyclosporine A, and granulocyte colony-stimulating factor (G-CSF) as well as granulocyte-macrophage colony-stimulating factor (GM-CSF). The efficacy of both GM- and G-CSF in reversing neutropenia and decreasing the risk of infections in Felty's syndrome and SLE has been well documented. Of concern, however, have been flares of symptoms or development of leukocytoclastic vasculitis in some patients following the use of these cytokines. Recent results suggest that in these patients G-CSF should be administered at the lowest dose effective at elevating the neutrophil count above 1,000/microL.

Complement activation in patients with rheumatoid arthritis mediated in part by C-reactive protein

OBJECTIVE

Complement activation in patients with rheumatoid arthritis (RA) is considered to be triggered by immune complexes. Recently, it was shown that C-reactive protein (CRP) can activate the complement system in vivo. We therefore hypothesized that part of the complement activation in RA is due to CRP. The aim of this study was to investigate CRP-mediated complement activation in RA, and to assess its correlation with disease activity.

METHODS

Complexes between CRP and the activated complement components C3d (C3d-CRP) and C4d (C4d-CRP), which reflect CRP-mediated complement activation, as well as the overall levels of activated C3 and C4 were measured in the plasma of 107 patients with active RA and 177 patients with inactive RA. Inactive RA was defined according to the American College of Rheumatology criteria for clinical remission. Disease activity was assessed by the modified Disease Activity Score (DAS28).

RESULTS

Plasma levels of C3d-CRP and C4d-CRP were increased in the majority of the patients, and were significantly higher in patients with active disease versus those with inactive RA (P < 0.001). In patients with active RA, the plasma concentrations of C3d-CRP and C4d-CRP correlated significantly with the DAS28 (Spearman's rho 0.61 and 0.55, respectively; P < 0.001), whereas these correlations were less pronounced in patients with inactive RA (Spearman's rho 0.28 [P < 0.001] and 0.25 [P = 0.001], respectively). Levels of activated C3 and C4 were also increased in the majority of the patients, particularly in patients with active RA.

CONCLUSION

Part of the activation of complement in RA is mediated by CRP and is correlated with disease activity. We suggest that this activation is involved in the pathogenesis of RA.

Cloning and expression of a novel human antibody-antigen pair associated with Felty's syndrome

An increasing number of studies suggest the importance of antibodies in the pathogenesis of most systemic and organ-specific autoimmune diseases, although there is considerable controversy over the precise role of the autoantibodies involved. In humans, a major obstacle to progress is the identification and cloning of the relevant autoantibodies and autoantigens. Here, an approach based on the sequential use of antibody phage display and antigen expression libraries is developed and applied to a donor suffering from rheumatoid arthritis (RA), splenomegaly, and peripheral destruction of neutrophils leading to neutropenia (Felty's syndrome). An antibody phage display library was constructed from bone marrow from the donor and a high-affinity human mAb, ANA15, selected by panning against fresh neutrophils and independently by panning against a fixed cell line. The antibody showed strong staining of neutrophils and a number of cell lines. Probing of a lambdagt11 expression library from an induced myelomonocytic cell line with the mAb ANA15 identified the eukaryotic elongation factor 1A-1 (eEF1A-1) as a novel autoantigen. The specificity of ANA15 was confirmed by reactivity with both purified and recombinant eEF1A-1. Screening of a large panel of sera revealed that 66% of patients with Felty's syndrome had elevated levels of anti-eEF1A-1 antibodies. The cloning of this antibody-antigen pair should permit rational evaluation of any pathogenicity resulting from the interaction and its significance in neutropenia.

Splenic involvement in rheumatic diseases

OBJECTIVES

To assess the major reports of splenic involvement in the rheumatic diseases and to highlight several conditions in which potentially life-threatening splenic complications may occur.

METHODS

A search of the Medline database ('SilverPlatter': 1966 to 1997) was conducted for all English-language entries related to the spleen and the major rheumatic diseases. Original articles were reviewed from the bibliographies of these Medline-sourced articles. The major rheumatological textbooks were also reviewed for original references.

RESULTS

Patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and polyarteritis nodosa (PAN) are at risk of experiencing spontaneous splenic rupture. Splenomegaly is common in both uncomplicated RA and as a feature of Felty's syndrome, in which the patient may be at risk of splenic abscess formation, again a possible complication of SLE and also PAN. Massive splenomegaly appears to be specific to SLE and may be confused with a malignant process. Abnormal splenic function has been documented in RA, SLE, and Wegener's granulomatosis. The spleen may show areas of infarction in several conditions, notably SLE and Wegener's granulomatosis. Splenic atrophy is not uncommon in SLE and may be associated with functional asplenia and a co-incident risk of potentially fatal infection with capsulated organisms.

CONCLUSIONS

Serious and occasionally fatal complications within the spleen occur in many rheumatic diseases. Prompt recognition of these complications is important.

Successful reversal of neutropenia in Felty's syndrome with recombinant granulocyte colony stimulating factor

We report two patients with Felty's syndrome and chronic skin ulcers treated successfully with recombinant granulocyte colony stimulating factor (GCSF). In both cases granulocytes returned to the normal range within days of starting treatment, and their cutaneous ulcers improved. In one patient granulocytes were maintained at normal levels with a regimen of GCSF 3 micrograms/kg twice weekly for 14 months.

Felty's and pseudo-Felty's syndromes

Felty's syndrome, consisting of rheumatoid arthritis, leukopenia, and splenomegaly, has been recognized as a distinct clinical entity for more than 60 years. Clinical and laboratory manifestations of the condition are reviewed. The major sources of morbidity and mortality remain recurrent local and systemic infections. Immunogenetic analysis shows a strong association with HLA-DR4, in addition to DQ beta 3b and C4B null allele. Potential mechanisms of neutropenia are contrasted, including impaired granulopoiesis and neutrophil-immune complex interactions. Lithium carbonate and splenectomy may have a role in the treatment of fulminant disease. Maintenance therapy should be directed at control of the underlying inflammatory arthropathy. A syndrome of proliferation of large granular lymphocytes and neutropenia, associated with rheumatoid arthritis in 23% to 39% of cases, has been described recently. Cases of "pseudo-Felty's" syndrome are often confused with traditional Felty's syndrome, which has twice the prevalence. The clinical and laboratory distinctions between these two conditions are elaborated.

Cyclosporine for the treatment of granulocytopenia in Felty's syndrome

A patient with Felty's syndrome was treated with cyclosporine, initially 10 mg/kg/day and then 4 mg/kg/day. The neutrophil count increased by 6 weeks and was normal at 3 months. Over the subsequent 27 months the neutrophil count was closely related to the cyclosporine dosage and there was no evidence of cyclosporine toxicity. This case indicates that cyclosporine may have a role in the treatment of Felty's syndrome.

IgG and IgA antibodies to the collagen-like region of C1q in rheumatoid vasculitis

We investigated the presence of IgG and IgA antibodies to C1q in serum samples from 80 patients with rheumatoid arthritis (RA), 31 patients with rheumatoid vasculitis, and 80 healthy controls. IgG and IgA antibodies to C1q, as measured by enzyme-linked immunosorbent assay, were found in less than 5% of the sera from RA patients and from healthy controls. In contrast, IgG and IgA antibodies to C1q were found in 29% and 61%, respectively, of the sera from patients with rheumatoid vasculitis. The occurrence of IgA antibodies to C1q has not been previously demonstrated. These results also demonstrate that IgG antibodies to C1q do not occur exclusively in systemic lupus erythematosus patients: Sera of patients with rheumatoid vasculitis frequently contain IgG or IgA antibodies to C1q, which contribute to immune complex formation.

[Agranulocytosis and connectivitis different from Felty's syndrome: 4 cases. Success of cyclosporin in a case]

Four cases of chronic agranulocytosis in patients with systemic diseases different from Felty's syndrome are reported. Two patients had primary Sjögren's syndrome (confirmed in one, suspected in the other), one had systemic lupus erythematosus and the last patient had an unclassifiable connective tissue disease. Only one severe infection was recorded. The pathophysiological mechanisms involved are discussed. There is a strong suspicion that the cytopenia is of immune origin. Corticosteroid therapy was effective in all four patients. One patient who could not tolerate corticosteroids was successfully treated with cyclosporin A.

Reversal of neutropenia with methotrexate treatment in patients with Felty's syndrome. Correlation of response with neutrophil-reactive IgG

We evaluated the clinical and hematologic response to methotrexate (MTX) in 4 women with Felty's syndrome (FS) who had had neutropenia for 1-3 years. Since immune complexes or antineutrophil antibodies are implicated in the pathogenesis of the neutropenia of FS, we also measured both direct and indirect levels of neutrophil-reactive IgG. All 4 patients showed a prompt and dramatic increase in neutrophil counts within 1-2 months of starting MTX therapy. In 3 patients, the symptoms of arthritis also improved; in the fourth patient, arthritis worsened. Recurring infections ceased in 3 patients. Neutrophil-reactive IgG levels, which were elevated in all patients prior to treatment, decreased toward normal while the patients were receiving MTX therapy. We conclude that MTX is effective in treating the neutropenia of FS, in part by lowering neutrophil-reactive IgG.

Lack of evidence for the presence of neutrophil autoantibodies in the serum of patients with Felty's syndrome

Sera of 22 patients with Felty's syndrome and 14 patients with rheumatoid arthritis were tested in assays routinely used for the detection of neutrophil antibodies (i.e. immunofluorescence, agglutination and cytotoxicity tests) as well as in the antibody-dependent lymphocyte-mediated granulocytotoxicity test. One or more of the routinely used assays were positive in a high percentage of the sera (77% and 64%, respectively). The antibody-dependent lymphocyte-mediated granulocytotoxicity test was only positive with sera of three patients with Felty's syndrome. Positive results in the immunofluorescence and agglutination tests could be attributed to the presence of immune complexes in the sera, whereas positive antibody-dependent lymphocyte-mediated granulocytotoxicity tests were probably due to the presence of HLA alloantibodies. It is concluded that serological tests routinely used for the detection of neutrophil autoantibodies should be interpreted with caution in patients with Felty's syndrome. Our results also indicate that the neutropenia in Felty's syndrome is rarely, if ever, due to neutrophil-specific autoantibodies.

The spleen in Felty's syndrome: a histological, morphometrical, and immunohistochemical study

A histological study employing morphometrical and immunohistochemical methods was performed in 3 spleens removed because of Felty's syndrome (FS). A comparison was made with control spleens and with spleens removed from patients with idiopathic thrombocytopenic purpura (ITP) or autoimmune hemolytic anemia (AIHA). In FS, the spleen is enlarged, mainly due to expansion of the red pulp. The sinuses are enlarged, too, and contain many macrophages. 2 of our specimens showed many hyperplastic germinal centers; the 3rd contained no germinal centers. Only in the former cases did splenectomy lead to an increase in the number of circulating granulocytes. Immunohistologically, FS spleens differed from the control, the ITP, and the AIHA spleens. The results have provided further evidence indicating that the pathogenesis of granulocytopenia in FS differs from that of autoimmune hematocytopenias, and have given rise to the hypothesis that, in FS, the spleen is the site of interaction between immune complexes and granulocytes.