Increased IgA antibodies to cytokeratins in the spondyloarthropathies

The adaptive immune response to porous regenerated keratin as a bone graft substitute in an ovine model

Reconstituted keratin is a novel bone graft material when prepared as a rigid scaffold. Understanding the immunogenicity of this material is important to determine whether this substance is a viable surgical option. Previous studies have shown no innate immune system activation in response to reconstituted keratin implants. To examine antibody-mediated immune responses to reconstituted keratin implants, bone and blood samples were taken from twelve sheep with surgically created tibial defects containing such implants. RT-PCR was used to detect mRNA of the inflammatory marker SOCS 3 in local bony tissue, and a novel immunohistochemistry assay developed to detect antikeratin antibodies in serum. Two animals were sacrificed per time-point at weeks 1, 2, 4, 6, 8 and 12. Time points for serum analysis included baseline (pre-surgery) and all other time points; mRNA analysis examined samples from all time points. No upregulation in antikeratin antibodies or SOCS 3 mRNA was observed at any time point, indicating that reconstituted keratin implants do not trigger an adaptive immune response in vivo in an ovine model. These findings provide the platform for further development of keratin implants in other mammalian models to define its immunogenic profile and safety.

Reactive arthritis

Reactive arthritis (ReA) is an immune-mediated seronegative arthritis that belongs to the group of spondyloarthropathies and develops after a gastrointestinal or genitourinary system infection. The condition is considered to be characterized by a triad of symptoms (conjunctivitis, arthritis and urethritis) although a constellation of other manifestations may also be present. ReA is characterized by psoriasiform dermatological manifestations that may resemble those of pustular psoriasis and, similar to guttate psoriasis, is a post-infectious entity. Also, the articular manifestations of the disorder are similar to those of psoriatic arthritis and both conditions show a correlation with HLA-B27. These facts have led several authors to suggest that there is a connection between ReA and psoriasis, listing ReA among the disorders related to psoriasis. However, the pathogenetic mechanism behind the condition is complex and poorly understood. Bacterial antigenicity, the type of host response (i.e. Th1/Th2 imbalance) and various genetic factors (i.e. HLA-B27 etc.) play an important role in the development of the disorder. It is unknown whether all the aforementioned factors are part of a mechanism that could be similar to, or share basic aspects with known psoriasis pathogenesis mechanisms.

Detection of multiple autoantibodies in patients with ankylosing spondylitis using nucleic acid programmable protein arrays

Ankylosing spondylitis (AS) is a common, inflammatory rheumatic disease that primarily affects the axial skeleton and is associated with sacroiliitis, uveitis, and enthesitis. Unlike other autoimmune rheumatic diseases, such as rheumatoid arthritis or systemic lupus erythematosus, autoantibodies have not yet been reported to be a feature of AS. We therefore wished to determine whether plasma from patients with AS contained autoantibodies and, if so, characterize and quantify this response in comparison to patients with rheumatoid arthritis (RA) and healthy controls. Two high density nucleic acid programmable protein arrays expressing a total of 3498 proteins were screened with plasma from 25 patients with AS, 17 with RA, and 25 healthy controls. Autoantigens identified were subjected to Ingenuity Pathway Analysis to determine the patterns of signaling cascades or tissue origin. 44% of patients with ankylosing spondylitis demonstrated a broad autoantibody response, as compared with 33% of patients with RA and only 8% of healthy controls. Individuals with AS demonstrated autoantibody responses to shared autoantigens, and 60% of autoantigens identified in the AS cohort were restricted to that group. The autoantibody responses in the AS patients were targeted toward connective, skeletal, and muscular tissue, unlike those of RA patients or healthy controls. Thus, patients with AS show evidence of systemic humoral autoimmunity and multispecific autoantibody production. Nucleic acid programmable protein arrays constitute a powerful tool to study autoimmune diseases.

Purified proteins from Leishmania amastigotes-induced delayed type hypersensitivity reactions and remission of collagen-induced arthritis in animal models

A treatment preparation composed of purified Leishmania (L) antigenic fractions (AS210) induced linear delayed type hypersensitivity (DTH) reactions over a 1-40 microg dose range, in guinea pigs. When a DBA-1 mouse collagen induced arthritis (CIA) model was used to compare AS210 treatment against: a polyvalent vaccine (AS110-1), a monovalent vaccine (AS110-2) and placebo, the AS210 treated mice had the least amount of forepaw inflammation and the lowest mean arthritis scores (MAS). When MAS for day(s) 1-40 were analyzed using one way ANOVA, statistically significant (P < 0.05) differences were seen for the following study groups: PBS versus Dexamethasone and PBS versus AS210. Subsequently, the ANOVA analysis results were corroborated by the Mann-Whitney test: analysis of the first group (P < 0.001) and analysis of the second group (P < 0.001). Comparison between dexamethasone and AS210 at different time intervals by Mann-Whitney test were as follows: day 0-day 5 both treatments had equal values (P = 1.00), from day-7 to 20 AS210 treatment had lower MAS values than dexamethasone (P = 0.037), and from day-21 to 30, AS210 MAS were similar to dexamethasone values (P = 0.319). No statistical difference was observed between AS110-1, AS110-2, and placebo groups.

Diagnosis and treatment of psoriatic arthritis

Psoriatic arthritis is a chronic, heterogeneous disease whose pathogenesis is unknown, although genetic, environmental, and immunologic factors play major roles. Psoriatic arthritis can follow an aggressive clinical course, and differentiating it from other arthropathies is sometimes difficult. Diagnosis of psoriatic arthritis is based on history, physical examination, the usual absence of rheumatoid factor, and characteristic radiographic features. At least 40% of patients with psoriatic arthritis develop radiographically detectable joint destruction; therefore, proper diagnosis and early treatment can have a significant impact on disease course and outcome. Understanding the pathogenesis of psoriatic disease has led to the use of several biologic agents that work by modulating T-cell signaling or by inhibiting key cytokines involved in inflammation, such as tumor necrosis factor (TNF). TNF inhibitors have demonstrated excellent efficacy in resolving skin and joint disease in patients with psoriatic arthritis and have been shown to be safe agents in various inflammatory disorders. This article reviews the diagnostic and treatment challenges of psoriatic arthritis as they relate to pathogenesis and burden of disease.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should have acquired a more comprehensive knowledge of our current understanding of the classification, clinical presentation, etiology, pathophysiology, differential diagnosis, and treatment of psoriatic arthritis.

Increased levels of antibodies to cytokeratin 18 in patients with rheumatoid arthritis and ischaemic heart disease

OBJECTIVE

To determine whether raised levels of antibodies to CK18 in patients with RA are associated with ischaemic heart disease (IHD).

METHODS

IgA, IgG, and IgM antibodies to CK18 were measured by enzyme linked immunosorbent assay (ELISA) in patients with RA with (n = 34) or without (n = 28) IHD. The relationship between CK18 antibody levels and markers of inflammatory and/or cardiovascular disease was examined.

RESULTS

Initial analysis showed that IgG antibody levels to CK18 were higher in patients with RA with IHD than in those without (50.1 v 34.5 AU, p = 0.047), although significance was lost after correction for multiple comparisons. Further analysis showed a significant difference (p = 0.015) between patients with IHD and a positive family history, and patients without IHD and a negative family history (53.7 v 29.0 AU, Kruskal-Wallis multiple comparison Z value test). There was also a significant trend of increasing 10 year cardiovascular risk with increasing CK18 IgG antibody levels (p = 0.01). No association was found between CK18 antibody levels and conventional markers of inflammation or cardiovascular disease, but an association was found between levels of CK18 IgG and IgG antibodies to cytomegalovirus (CMV) (Spearman's r(s) = 0.379, p(corr) = 0.04). No evidence for cross reactivity of CK18 antibodies with CMV antigens was found.

CONCLUSION

Levels of IgG antibodies to CK18 are raised in patients with RA with IHD, particularly if they also have a positive family history. This may reflect damage to CK18 containing cells in the cardiac vasculature and/or in atherosclerotic plaques, and may be a useful additional marker for the identification of patients with, or likely to develop, IHD.

The spectrum of cutaneous lesions in rheumatoid arthritis: a clinical and pathological study of 43 patients

INTRODUCTION

Rheumatoid arthritis (RA) is an idiopathic arthropathy syndrome that has a propensity to affect the small joints of the hands and feet with extra-articular manifestations comprising skin lesions, neuropathy, pericarditis, pleuritis, interstitial pulmonary fibrosis and a systemic polyarteritis nodosa (PAN)-like vasculitic syndrome. The most widely recognized skin lesion is the rheumatoid nodule. Other skin manifestations are poorly defined.

MATERIALS AND METHODS

Using a natural language search of the authors' outpatient dermatopathology databases, skin biopsies from 43 patients with RA were selected for retrospective analysis in an attempt to define the dermatopathological spectrum of RA and its clinical correlates.

RESULTS

The biopsies were categorized by the dominant histologic pattern, recognizing that in most cases there were additional minor reaction patterns. Palisading and/or diffuse interstitial granulomatous inflammation was the dominant pattern seen in 21 patients; the lesions included nodules, plaques and papules with a predilection to involve skin over joints. Besides interstitial histiocytic infiltrates and variable collagen necrobiosis, these cases also showed interstitial neutrophilia, vasculitis and pauci-inflammatory vascular thrombosis. The dominant morphology in 11 other patients was vasculopathic in nature: pauci-inflammatory vascular thrombosis, glomeruloid neovascularization, a neutrophilic vasculitis of pustular, folliculocentric, leukocytoclastic or benign cutaneous PAN types, granulomatous vasculitis, and lymphocytic vasculitis and finally occlusive intravascular histiocytic foci for which the designation of "RA-associated intravascular histiocytopathy" is proposed. Rheumatoid factor (RF) positivity and active arthritis were common in this group, with anti-Ro and anticardiolipin antibodies being co-factors contributing to vascular injury in some cases. Immunofluorescent testing in three patients revealed dominant vascular IgA deposition. In nine patients, the main pattern was one of neutrophilic dermal and/or subcuticular infiltrates manifested clinically as urticarial plaques, pyoderma gangrenosum and panniculitis.

CONCLUSIONS

The cutaneous manifestations of RA are varied and encompass a number of entities, some of which define the dominant clinical features, such as the rheumatoid papule or subcutaneous cords, while others allude to the histopathology, i.e. rheumatoid neutrophilic dermatosis. We propose a more simplified classification scheme using the adjectival modifiers of "rheumatoid-associated" and then further categorizing the lesion according to the dominant reaction pattern. Three principal reaction patterns are recognized, namely extravascular palisading granulomatous inflammation, interstitial and/or subcuticular neutrophilia and active vasculopathy encompassing lymphocyte-dominant, neutrophil-rich and granulomatous vasculitis. In most cases, an overlap of the three reaction patterns is seen. Co-factors for the vascular injury that we believe are integral to the skin lesions of RA include RF, anti-endothelial antibodies of IgA class, anti-Ro and anticardiolipin antibodies.

Immunoglobulin A-associated lymphocytic vasculopathy: a clinicopathologic study of eight patients

INTRODUCTION

Cutaneous IgA-associated vasculitis can be a clue to Henoch-Schönlein purpura (HSP), which typically comprises renal and gastrointestinal tract disease and arthritis, whereby prominent and predominant IgA deposits within the cutaneous vasculature provoke a pustular leukocytoclastic vasculitis.

DESIGN

We describe eight patients with a novel expression of a cutaneous IgA vascular injury syndrome, namely a lymphoid vasculopathy which clinically and light microscopically resembled a pigmentary purpura (PP) in six, and correlate direct immunofluorescence (DIF) and clinical features to light microscopy.

RESULTS

Among associated diseases were prior viral infection, an HSP symptom complex, an undifferentiated connective tissue disease syndrome, lupus erythematosus profundus (LEP), Degos' disease and Berger's disease. Skin lesions comprised non-palpable petechial lesions involving lower extremities in all cases and also the upper extremities in two. A superficial perivascular lymphocytic infiltrate unaccompanied by vascular fibrin deposits was associated with prominent erythrocyte extravasation including into the epidermis. Mural and extravascular fibrin deposition was seen in one biopsy from a PP-like lesion and mural fibrinoid necrosis was seen in the cases of LEP and Degos' disease; in biopsies from these three cases, the presence of fibrin deposition warranted use of the appellation 'lymphocytic vasculitis'. In all patients, DIF showed prominent and predominant IgA deposits.

CONCLUSIONS

A non-necrotizing lymphocytic purpuric vascular reaction is one manifestation of vascular IgA deposition in the skin. A subpopulation of human lymphocytes bear surface Fc receptor and/or C3 receptors ('complement receptor lymphocytes') which can bind circulating immune complexes (ICs) or C3 generated via activation of the alternative complement cascade. Thus, circulating ICs are a potential pathogenic basis of this eruption, the histologic differential diagnosis of which is idiopathic PP and PP of drug or viral etiology.

HLA-B27 associated spondyloarthropathy, an autoimmune disease based on crossreactivity between bacteria and HLA-B27?

Most autoimmune diseases are associated with certain HLA types. Therefore, spondyloarthropathies (SpA) strongly associated with HLA-B27, are also often classified as autoimmune diseases. This study questions whether SpA indeed fulfils the criteria of an autoimmune disease. The Medline database was searched for all reports between 1966 and April 1998 on the presence of autoimmune reactivity in SpA patients. This search yielded 45 articles on this subject. Only eight articles study T cell reactivity. Twelve reports were found on the assessment of antibodies crossreacting between bacteria and HLA-B27. In the 45 studies demonstrating autoimmune reactions in SpA patients proper controls matched for HLA-B27, sex and age were nearly always lacking. Therefore, it is concluded that the frequency of increased autoreactivity in sera from patients and controls is not significantly different, and that this lack of autoreactivity does not justify classification of SpA as an autoimmune disease. As crossreactive antibodies against bacteria and HLA-B27 were equally present in sera from patients and controls, the pathogenetic significance of molecular mimicry between various bacteria and HLA-B27 is questionable. Furthermore, the regions of the B27 molecule that are supposed to be crossreactive with bacteria, differ in one or more amino acids among the distinct B27 subtypes. Although these differences strongly influence the binding of antibodies to the B27 molecule, there was no relation between the degree of crossreactivity of certain subtypes and the association of these subtypes with SpA. In conclusion, there is no evident proof that SpA is an autoimmune disease attributable to crossreactivity between bacteria and HLA-B27.

A clinical and histologic study of 37 cases of immunoglobulin A-associated vasculitis

Immunoglobulin (Ig) A-associated vasculitis is commonly equated with the multiorgan systemic vasculitic syndrome Henoch-Schonlein purpura (HSP), which occurs predominantly in the pediatric age group. By natural language search of the databases of two outpatient dermatopathology practices, the authors selected for review 37 cases of IgA-associated vasculitis, 23 of which were associated with antecedent infection, most commonly of the upper respiratory tract. Criteria for a diagnosis of HSP were met in 15 cases, 13 of which were in the setting of prior infection. Lower extremity skin involvement was ubiquitous. A more widespread form of vasculitis was also seen, particularly in the setting of previous infection. Several of the patients with previous infection had underlying medical illnesses including rheumatoid arthritis, atopy, renal failure, lupus erythematosus, insulin dependent diabetes mellitus, autoimmune thyroid disease, and Wegener's granulomatosis. In those patients lacking an apparent microbial trigger, Sjogren's disease with anti-Ro antibodies and hypergammaglobulinemia, lupus erythematosus, inflammatory bowel disease, IgA paraproteinemia, bronchogenic and prostatic carcinoma, cryoglobulinemia, and lymphoma were uncovered. Regardless of whether an infectious stimulus was implicated, certain cofactors with the potential to enhance vascular injury were uncovered; these included anti-Ro antibodies, antineutrophil cytoplasmic antibody, diabetic microangiopathy, and a hyperviscosity state. In the infective group, a pustular vasculitis, defined as a neutrophilic vascular reaction in concert with epithelial pustulation, was seen in 81% of cases versus 33% in the noninfectious group (p = 0.02). The prototypic histomorphology in the noninfective group was one of a mild cell poor leukocytoclastic vasculitis; Vasculitis was of greater severity in patients with antecedent infection (p = 0.026). An infectious trigger, typically of mucosal origin, can frequently be identified in patients with cutaneous IgA-associated vasculitis, especially those with the symptom complex of HSP. The light microscopy appears to distinguish patients who have an infectious trigger from those who do not. IgA-associated vasculitis may be a clue to the presence of certain underlying disorders where there is immune dysregulation or enhanced susceptibility to immune complex entrapment.

Sterile neutrophilic folliculitis with perifollicular vasculopathy: a distinctive cutaneous reaction pattern reflecting systemic disease

The authors prospectively encountered skin biopsies from 20 patients which demonstrated a neutrophilic or suppurative and granulomatous folliculitis accompanied by a folliculocentric neutrophilic vascular reaction of Sweet's-like or leukocytoclastic vasculitis subtypes. While in each case the histomorphology raised diagnostic consideration of bacterial folliculitis, patients frequently expressed systemic complaints such as arthritis, fever, and malaise, and special stains for micro-organisms were negative. Among the clinical presentations were folliculitis, vasculitis, acneiform eruptions, vesiculopustular lesions, and erythema nodosum-like lesions, with the legs, arms, and upper back being the most commonly involved sites. Nineteen patients were found to have specific underlying systemic diseases, namely, inflammatory bowel disease, Reiter's disease, Behçet's disease, hepatitis B, connective tissue disease including mixed connective tissue disease and rheumatoid arthritis, scrofuloderma, and hematologic dyscrasias. The other patient had antecedent bacterial sinusitis in the setting of atopy. The folliculocentric nature of these lesions may reflect preferential processing of antigens through the hair follicle and/or homology between bacterial and follicular heat shock proteins in the susceptible host, namely, one who responds excessively to exogenous antigenic triggers. Folliculitis with folliculocentric vasculopathy may be a clue to underlying systemic disease and/or an extracutaneous infection. Certain light microscopic features in concert with the clinical presentation may distinguish such cases from conventional infectious folliculitis.

Anticytokeratins are a potential source of false-positive indirect immunofluorescence assays for C-ANCA

Antibodies to neutrophil cytoplasmic antigens (ANCA) targeted toward granule enzymes have been recognized as a valuable diagnostic tool in the detection of Wegener's granulomatosis and systemic vasculitides. However, the most commonly used method of detection, the indirect immunofluorescence assay, is prone to false-positive results due to antibodies of different pathological significance either targeted to, or cross-reacting with, similarly distributed epitopes. Using double immunofluorescence, the present study demonstrates that anticytokeratin antibodies are able to produce false-positive C-ANCA immunofluorescence assays. In addition, a case of natural appearance of cytokeratin-reactive antibodies causing a false-positive "pseudo-ANCA" staining pattern in a patient presenting with sepsis is reported. Since the expression of cytokeratins is almost exclusively confined to epithelial cells, the most plausible explanation for both phenomena is a crossreaction of anticytokeratin antibodies with granule associated epitopes. Due to the natural appearance of anticytokeratin antibodies in association with a variety of other pathologic entities, it is of crucial importance for the diagnostic significance of the C-ANCA immunofluorescence assay to exclude anticytokeratin caused false-positive results. It is shown that supplementary indirect immunofluorescence tests performed on cultured human epithelial cells readily distinguish anticytokeratin caused "pseudo-ANCA" from true C-ANCA.

Antibodies to cytokeratins in inflammatory arthropathies

OBJECTIVES

Cytokeratins are a major constituent of the cytoskeleton in eukaryotic cells and are vital for the maintenance of cell structure and function. Identification of increased levels of IgA antibodies to these intracellular structures has prompted increasing interest in the potential role between the gut and the immune system in the pathogenesis of inflammatory arthritis. This review examines the salient features of cytokeratin (CK) antibodies that are relevant to inflammatory arthropathies and discusses the meaning and potential applications of these findings in the context of the different arthropathies.

METHODS

Review of the literature on antibodies to cytokeratins in inflammatory arthropathies, using MEDLINE and the key words (cyto)keratin and arthritis. The studies were interpreted and critiqued.

RESULTS

Increased levels of IgA antibodies to CK-18 and epidermal keratins have been shown by enzyme-linked immunosorbent assay (ELISA) in rheumatoid arthritis and psoriatic arthritis. Levels were not increased in osteoarthritis or reactive arthritis.

CONCLUSIONS

CK-18 is present within endothelial cells lining synovial blood vessels in patients with various rheumatic conditions, including rheumatoid arthritis, as well as in normal controls. Damage to synovial endothelial cells may lead to increased production of antibodies to CK-18. The CK antibody response is independent of the polyclonal immunoglobulin expansion typical of RA and is not specific for RA because an increased IgA response to CK-18 also has been shown in psoriasis and in psoriatic arthritis. Damage to synovial endothelial cells does not explain the increased autoantibody production in other conditions such as psoriasis. In this condition, damage to epithelial tissues in other regions of the body (e.g, skin, gut, kidney) may lead to production of keratin antibodies that recognize epitopes common to all CK, including CK-18. The reason for an elevated IgA anti-CK response rather than an IgG or IgM response is not clear. It cannot be explained by a general increase in serum IgA levels. Most of the conditions in which raised levels of these antibodies were found have been associated to different degrees with abnormalities of the gut mucosa or mucosal immune system. It appears that the nature of autoantibodies to CK-18 is probably natural rather than pathogenic. Currently there are no data on the source of the IgA antibodies to cytokeratins (i.e., mucosal or central immune system). Indeed, it may depend on the disease.