Histologic and electron microscopic characterization of the antiperinuclear factor antigen

Anti-perinuclear Factor as Diagnostic Marker in Rheumatoid Arthritis

INTRODUCTION

Rheumatoid Arthritis (RA) is a systemic autoimmune disease. It is associated with several auto antibodies which can serve as diagnostic and prognostic markers.

AIM

In this study, Anti perinuclear Factor (APF) was evaluated as a biomarker in comparison with Rheumatoid Factor (RF) in Rheumatoid Arthritis.

MATERIALS AND METHODS

Fifty two sera of patients with RA (mean age 48±15.8), 23 sera of Patient control group (mean age 32.5 ± 16.9) and 30 sera of Healthy control group (mean age 32.1± 16.9) were analysed. The method is based on the binding of APF to perinuclear keratohyalin granules of buccal mucosal cell and its detection using a fluorescently labeled anti human total antiserum.

RESULTS

APF were found in 71.2 %(37/52) of patients with RA. The sensitivity and specificity for APF from 1/5 serum dilution was 71.2% and 94.3% respectively. RF test had higher sensitivity (88.5%) compare to the APF test (71.2%), but its specificity was (86.8%) less than APF (94.3%). There was no significant relationship between the onset of APF and severity of disease but there was significant relationship between the APF titer and severity of disease (p<0.05).

CONCLUSION

It is concluded that APF test is a valuable serological tool for the diagnosis of the disease and a useful serological marker to differentiate from the other inflammatory rheumatoid diseases.

Autoantibody explosion in systemic lupus erythematosus: more than 100 different antibodies found in SLE patients

OBJECTIVE

Description of the various autoantibodies that can be detected in patients with systemic lupus erythematosus (SLE).

METHODS

A literature review, using the terms "autoantibody" and "systemic lupus erythematosus", was conducted to search for articles on autoantibodies in SLE, their target antigens, association with disease activity, or other clinical associations.

RESULTS

One hundred sixteen autoantibodies were described in SLE patients. These include autoantibodies that target nuclear antigens, cytoplasmic antigens, cell membrane antigens, phospholipid-associated antigens, blood cells, endothelial cells, and nervous system antigens, plasma proteins, matrix proteins, and miscellaneous antigens. The target of autoantibody, the autoantigen properties, autoantibody frequencies in SLE, as well as clinical associations, and correlation with disease activity are described for all 116 autoantibodies.

CONCLUSIONS

SLE is the autoimmune disease with the largest number of detectable autoantibodies. Their production could be antigen-driven, the result of polyclonal B cell activation, impaired apoptotic pathways, or the outcome of idiotypic network dysregulation.

In the rheumatoid pannus, anti-filaggrin autoantibodies are produced by local plasma cells and constitute a higher proportion of IgG than in synovial fluid and serum

IgG anti-filaggrin autoantibodies (AFA) are the most specific serological markers of rheumatoid arthritis (RA). They include the so-called 'anti-keratin antibodies' (AKA) and anti-perinuclear factor (APF), and recognize human epidermal filaggrin and other (pro)filaggrin-related proteins of various epithelial tissues. In this study we demonstrate that AFA are produced in rheumatoid synovial joints. In 31 RA patients, AFA levels were assayed at equal IgG concentrations in paired synovial fluids (SF) and sera. AFA titre-like values determined by indirect immunofluorescence and immunoblotting and AFA concentrations determined by ELISA were non-significantly different in serum and SF, clearly indicating that AFA are not concentrated in SF. In contrast, we demonstrated that AFA are enriched in RA synovial membranes, since the ELISA-determined AFA in low ionic-strength extracts of synovial tissue from four RA patients represented a 7.5-fold higher proportion of total IgG than in paired sera. When small synovial tissue explants from RA patients were cultured for a period of 5 weeks, the profile of IgG and AFA released in the culture supernatants was first consistent with passive diffusion of the tissue-infiltrating IgG (including AFA) over the first day of culture, then with a de novo synthesis of IgG and AFA. Therefore, AFA-secreting plasma cells are present in the synovial tissue of RA patients and AFA can represent a significant proportion of the IgG secreted within the rheumatoid pannus.

Anti-perinuclear factor compared with the so called "antikeratin" antibodies and antibodies to human epidermis filaggrin, in the diagnosis of arthritides

OBJECTIVE

Antiperinuclear factor (APF), "antikeratin antibodies" ("AKA"), and antibodies to human epidermis filaggrin (AFA), are highly specific serological markers of rheumatoid arthritis (RA), which recognise epitopes on various isoforms of (pro)filaggrin. It was proposed that these antibodies are globally named antifilaggrin autoantibodies. Here the diagnostic value of the detection of each one is compared and the overlap between the three tests evaluated.

METHODS

492 serum samples were tested, including 279 RA serum samples, taken from patients in France and Belgium. APF and "AKA" titres were estimated by indirect immunofluorescence, and AFA titres by immunoblotting on filaggrin enriched human epidermis extracts.

RESULTS

By a convenient choice of the positivity thresholds, the diagnostic sensitivity and specificity of the tests were shown to be similar (0.52 and 0.97, respectively). Although the antibody titres were strongly correlated, the associations APF-AFA or AFA-"AKA" permitted more than 52% or 55% of RA to be diagnosed, with a specificity of 0.99.

CONCLUSION

APF, "AKA", and AFA detection have a similar diagnostic value. However, because the three tests do not totally overlap, associating APF with "AKA" or AFA with "AKA" can improve diagnostic sensitivity. None of the three antigens used bear all the epitopes recognised by antifilaggrin autoantibodies.

Antiperinuclear factor: a useful test for the diagnosis of rheumatoid arthritis

The objective of this study was to determine: (1) the diagnostic value of antiperinuclear factor (APF), (2) the types of immunoglobulins involved in the reaction and (3) the presence of the antibody in paired samples of serum and synovial fluid (SF). We studied 408 serum samples from the following: healthy controls (n = 68), patients with rheumatoid arthritis RA; n = 160, 106 RF-positive and 54 RF-negative and patients with other rheumatic diseases (n = 180). We examined paired serum and SF samples in 27 patients (8 with RA and 19 with other rheumatic conditions). APF was determined by an indirect immunofluorescence assay. A group of 30 APF-positive serum samples was incubated with fluorescent-labelled antisera against IgG, IgM and IgA independently. APF was positive in 55.7% of patients with RF-positive RA, in 35.2% of patients with RF-negative RA, in 11.1% of patients with other rheumatic diseases and in 5.9% of healthy controls. Statistical differences were found between RF-positive RA and the other three groups (P = 0.02, P = 0.0001, P = 0.0001, respectively) and between RF-negative RA and the groups of other rheumatic diseases (P = 0.0001) and healthy controls (P = 0.005). The specificity of the test for RA was 90.2%. APF was present in three SF samples from RA patients (37.5%). The reaction was mediated by immunoglobulins of the IgG class in 100% of those tested, and, in addition, 30% were of IgA and 6.7% of IgM classes. We concluded that APF is a good diagnostic test that could be included in the classification criteria of RA, it can be present in SF and it is predominantly an antibody of the IgG class.

Antiperinuclear factor in the diagnosis of juvenile rheumatoid arthritis

The antiperinuclear factor (APF) was estimated by immunofluorescent microscopy in the sera of 32 children and adolescents with juvenile rheumatoid arthritis (JRA) in comparison to a group of 16 children and adolescents with other rheumatologic disorders and a group of 20 age-matched healthy subjects. The APF was detected in 17 children with JRA (53%), in only one patient in the group of other rheumatologic disorders (6%), and in 2 healthy children (10%). Accordingly, APF had a sensitivity of 53%, a specificity of 92%, and a diagnostic efficiency of 74% in our series. APF was found to have a higher diagnostic gain in rheumatoid factor (RF) seronegative cases than did the RF in APF negative cases, meaning a higher sensitivity of APF as compared to the RF. The APF seropositivity was neither altered by the use of corticosteroids nor influenced by the age, gender, duration of illness, or number of joints affected. Three out of 5 patients with JRA had the APF detected in their synovial fluid; they were running rather a severe course of illness. The use of the APF could be an aid in the diagnosis of JRA.

The antiperinuclear factor and the so-called antikeratin antibodies are the same rheumatoid arthritis-specific autoantibodies

The so-called antikeratin antibodies (AKA) and the antiperinuclear factor (APF) are the most specific serological markers of RA. Using indirect immunofluorescence, AKA label the stratum corneum of various cornified epithelia and APF the keratohyalin granules of human buccal mucosa epithelium. We recently demonstrated that AKA recognize human epidermal filaggrin. Here, we report the identification of the major APF antigen as a diffuse protein band of 200-400 kD. This protein is seen to be closely related to human epidermal (pro) filaggrin since it was recognized by four antifilaggrin mAbs specific for different epitopes, and since the APF titers of RA sera were found to be correlated to their AKA titers and to their immunoblotting reactivities to filaggrin. Immunoabsorption of RA sera on purified epidermal filaggrin abolished their reactivities to the granules of buccal epithelial cells and to the 200-400-kD antigen. Moreover, antifilaggrin autoantibodies, i.e., AKA, affinity purified from RA sera, were shown to immunodetect the 200-400-kD antigen and to stain these granules. These results indicate that AKA and APF are largely the same autoantibodies. They recognize human epidermal filaggrin and (pro) filaggrin-related proteins of buccal epithelial cells. Identification of the epitopes recognized by these autoantibodies, which we propose to name antifilaggrin autoantibodies, will certainly open new paths of research into the pathophysiology of RA.

Antiperinuclear factor in the polyarticular form of juvenile chronic arthritis: are use of frozen material or age of patients relevant?

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Occurrence of antiperinuclear, antikeratin, and anti-RA 33 antibodies in juvenile chronic arthritis

OBJECTIVES

Antiperinuclear factor (APF), antikeratin antibodies (AKA), and anti-RA 33 antibodies are currently considered to be good markers for the diagnosis of adult rheumatoid arthritis with or without rheumatoid factor (RF). The prevalence of these markers was retrospectively reviewed in children with juvenile chronic arthritis (JCA) to determine whether they were associated with specific features.

METHODS

One hundred and twenty-four patients with JCA participated in this study. Controls included 28 patients with juvenile systemic lupus erythematosus and 21 healthy children. Antiperinuclear factor and AKA were determined by indirect immunofluorescence on buccal mucosal cells and oesophagus sections respectively. Anti-RA 33 antibodies were detected using a Western blot technique on HeLa cell nuclear extract.

RESULTS

Antiperinuclear factor was virtually absent in all the tested subgroups and anti-RA 33 antibodies were detected only in a subset of patients with RF positive polyarticular onset. Antikeratin antibodies were found in 27% of all children with JCA and in 42% of those with RF negative polyarticular onset. These results were statistically significant compared with healthy controls, but the presence of AKA was not specific to any patient subgroup. Moreover, in contrast with previous studies in adult RA, no relation was found between the presence of AKA and disease severity or activity.

CONCLUSION

These data suggest that APF, AKA, and anti-RA 33 antibodies are not useful for the diagnosis or classification of JCA.

The perinuclear factor, a rheumatoid arthritis-specific autoantigen, is not present in keratohyalin granules of cultured buccal mucosa cells

Rheumatoid arthritis patients have antibodies in their serum directed against the perinuclear factor, a protein component present in keratohyalin granules in the cytoplasm of human buccal mucosa cells. The anti-perinuclear factor (APF) can only be detected by an indirect immunofluorescence test performed on fresh buccal mucosa cells from 'selected donors'. To obtain a more reliable antigen source and to gain more insight into the origin and nature of the perinuclear factor we attempted to culture perinuclear factor-containing buccal mucosa cells. Here we describe the successful culturing of such cells, which, however, did not contain keratohyalin granules nor the perinuclear factor. By adding the phorbol ester 12-o-tetradecanoylphorbol-13-acetate (TPA) we were able to induce keratohyalin granules in both cultured primary buccal mucosa cells and a squamous carcinoma cell line of the cheek (SqCC/Y1). These induced keratohyalin granules do contain the protein profilaggrin, which in vivo, in fresh buccal mucosa cells, co-localizes with the perinuclear factor. However, we were not able to demonstrate the presence of the perinuclear factor, not even after induction of terminal differentiation of the cultured cells nor after Epstein-Barr virus infection. Our results suggest that the perinuclear factor, in contrast to profilaggrin, is not an integral component of buccal mucosa cells.