Substrate For Indirect Immunofluorescence Research Articles

DP04: Utility of human oesophagus as a substrate for indirect immunofluorescence in pemphigus: a descriptive study

DP04: Utility of human oesophagus as a substrate for indirect immunofluorescence in pemphigus: a descriptive study

Plucked Hair as a Substrate for Indirect Immunofluorescence in Cases of Pemphigus Vulgaris.

Introduction:Indirect immunofluorescence (IIF) is used to determine the circulating autoantibodies in cases of Pemphigus. For IIF in Pemphigus several substrates had been used. This study was done to determine whether plucked hair can be utilized as a substrate for IIF in cases of Pemphigus. Aim & Objectives: To determine the efficacy of utilizing the plucked hair as a substrate for indirect immunofluorescence among patients with Pemphigus vulgaris.Methodology:Thirty two consecutive patients with active and fresh diagnosed cases of pemphigus vulgaris (PV) who did not undergo any treatment and those patients who had positive DIF findings of characteristic fish net or chicken wire pattern of intercellular IgG deposits in the epidermis of perilesional skin were included in the study. A total of 32 control subjects without any auto immune disorders were selected and the blood samples were taken from these patients for IIF analysis. Anagen hair were collected from the healthy volunteers without pemphigus in the same way as for trichogram. Telogen hair were obtained by combing the hair and collecting the loose strands of hair on the comb and further confirmed under microscope. Three hairs each of anagen and telogen stage were collected from each subject to be utilized as a substrate for IIF.Results:Out of 32 samples 20 samples showed positive results for Ig G alone and 5 samples showed positivity for Ig G and C3. One sample showed positivity for C3alone. All these 26 samples were considered to have positive IIF test based on the intercellular pattern of deposit. Positive IIF results were observed in anagen hair samples and were negative in all the telogen hair samples. Six anagen hair samples did not show any positive findings in IIF for the study group. All the 32 control samples showed negative reports in IIF.Conclusion:In conclusion, IIF microscopy on plucked hair as a substrate is a more sensitive immunoassay for the detection of circulating intercellular autoantibodies in PV and the lower negative predictive value of this substrate is a limitation. Further large scale studies might provide better information regarding the practical utility.

Study of utility of oral epithelium as a substrate for indirect immunofluorescence in pemphigus

Study of utility of oral epithelium as a substrate for indirect immunofluorescence in pemphigus

New genetically engineered DFS70 knock-out HEp-2 cells enable rapid and specific recognition of anti-DFS70 antibodies

Background: The correct identification of anti-dense fine speckled-70 (DFS70) antibodies represents an important issue in the detection of anti-nuclear antibodies (ANAs) as performed by the indirect immunofluorescence (IIF) test on HEp-2 substrates. In this study, we have evaluated a new method for anti-DFS70 antibody detection employing HEp-2 cells knocked-out for the DFS70 antigen.Methods: We studied 148 sera with a DFS70-like pattern (91 positive and 57 negative when tested for anti-DFS70 antibodies by a specific chemoluminescence [CLIA] method); 116 sera with infectious disease; 100 healthy donors (HDs), 139 samples from patients with a defined diagnosis of autoimmune rheumatic disease (ARD), and 242 consecutive unselected samples screened for ANA during the routine work-up.Results: The HEp2 DFS70-Ko substrate recognized anti-DFS70 antibodies in 86/91 (94.5%) of the DFS70 CLIA-positive sera and in 9/57 (15.8%) of the DFS70 CLIA-negative samples. None of the 116 infectious diseases were positive for DFS70 using the engineered IIF substrate. Two samples (2%) were positive among HDs and were then confirmed by CLIA. The 139 ANA-positive sera from patients with ARD displaying a defined antibody specificity showed their expected patterns also on DFS70-Ko HEp-2 substrate. Five of the 242 (2.1%) consecutive samples tested in the routine ANA-screening were identified as DFS70-positive using the HEp2 Ko-substrate and were then confirmed by CLIA.Conclusions: The use of DFS70 HEp-2 Ko cells may offer the unique possibility of simultaneously identifying and confirming the presence of anti-DFS70 antibodies during the standard ANA evaluation, while keeping the expression of other autoantibody markers intact.

Simultaneous Distinction of Monospecific and Mixed DFS70 Patterns During ANA Screening with a Novel HEp-2 ELITE/DFS70 Knockout Substrate

Systemic autoimmune connective tissue disorders are characterized by circulating antinuclear antibodies (ANA). Although there are several technologies available for ANA screening, indirect immunofluorescence (IIF) using Human epithelial cells-2 (HEp-2) substrate remains the primary and recommended method because of its superior sensitivity. HEp-2 substrates can detect a multitude of patterns resulting from autoantibody binding to various protein and nucleic acid autoantigens distributed throughout the nucleus and cytoplasm of the cells. The great diversity of monospecific and mixed patterns resulting from positive reactions on HEp-2 substrate also complicate the interpretation and accuracy of reporting. One specific example which received utmost attention recently is the dense fine speckled 70 (DFS70) pattern resulting from autoantibodies that specifically bind to a protein called lens epithelium derived growth factor (LEDGF). Lack of clear association with a specific systemic autoimmune disease and high prevalence in healthy populations have made accurate interpretation of DFS70 pattern important. Accurate distinction of DFS70 pattern from disease-associated patterns using conventional HEp-2 substrate is challenging. Moreover, frequent co-occurrence of DFS70 pattern along with disease-associated patterns such as homogeneous, speckled, and mixed homogeneous-speckled patterns complicate the IIF interpretation. The goal of this paper is to demonstrate the utility of a novel engineered HEp-2 IIF substrate that retains all advantages of conventional HEp-2 substrate while simultaneously providing the ability to distinguish DFS70 pattern with high confidence in both monospecific and mixed ANA positive examples. The new substrate is further able to unmask disease-associated ANA patterns previously concealed by DFS70 pattern.

Simultaneous Distinction of Monospecific and Mixed DFS70 Patterns During ANA Screening with a Novel HEp-2 ELITE/DFS70 Knockout Substrate.

Systemic autoimmune connective tissue disorders are characterized by circulating antinuclear antibodies (ANA). Although there are several technologies available for ANA screening, indirect immunofluorescence (IIF) using Human epithelial cells-2 (HEp-2) substrate remains the primary and recommended method because of its superior sensitivity. HEp-2 substrates can detect a multitude of patterns resulting from autoantibody binding to various protein and nucleic acid autoantigens distributed throughout the nucleus and cytoplasm of the cells. The great diversity of monospecific and mixed patterns resulting from positive reactions on HEp-2 substrate also complicate the interpretation and accuracy of reporting. One specific example which received utmost attention recently is the dense fine speckled 70 (DFS70) pattern resulting from autoantibodies that specifically bind to a protein called lens epithelium derived growth factor (LEDGF). Lack of clear association with a specific systemic autoimmune disease and high prevalence in healthy populations have made accurate interpretation of DFS70 pattern important. Accurate distinction of DFS70 pattern from disease-associated patterns using conventional HEp-2 substrate is challenging. Moreover, frequent co-occurrence of DFS70 pattern along with disease-associated patterns such as homogeneous, speckled, and mixed homogeneous-speckled patterns complicate the IIF interpretation. The goal of this paper is to demonstrate the utility of a novel engineered HEp-2 IIF substrate that retains all advantages of conventional HEp-2 substrate while simultaneously providing the ability to distinguish DFS70 pattern with high confidence in both monospecific and mixed ANA positive examples. The new substrate is further able to unmask disease-associated ANA patterns previously concealed by DFS70 pattern.

Neutrophil Extracellular Traps Contain Selected Antigens of Anti-Neutrophil Cytoplasmic Antibodies.

Neutrophil extracellular traps (NETs) are chromatin filaments decorated with enzymes from neutrophil cytoplasmic granules. Anti-neutrophil cytoplasmic antibodies (ANCAs) bind to enzymes from neutrophil cytoplasmic granules and are biomarkers for the diagnosis of systemic vasculitides. ANCA diagnostics are based on indirect immunofluorescence (IIF) of ethanol-fixed neutrophils. IIF shows a cytoplasmic staining pattern (C-ANCA) due to autoantibodies against proteinase 3 (PR3) or a perinuclear staining pattern (P-ANCA) due to autoantibodies against myeloperoxidase (MPO). The distinct ANCA-staining patterns are an artifact of ethanol fixation. Here, we tested NETs as a substrate for the detection of ANCAs in human sera. We observed that P-ANCAs specifically stained NETs, while C-ANCAs targeted the cell bodies of netting neutrophils. The distinct ANCA-staining patterns were caused by the presence of MPO, but not PR3, in NETs. Using NETs as a substrate for IIF, we characterized ANCAs in sera of patients with ANCA-associated vasculitis (AAV). Furthermore, we inhibited serine proteases by diisopropylfluorophosphate to prevent chromatin unfolding and the release of NETs and thus generated neutrophils with MPO-positive nuclei and PR3-positive cytoplasm, which resembled the appearance of ethanol-fixed neutrophils. In conclusion, our data suggest that NETs are selectively loaded with antigens recognized by P-ANCAs, and netting neutrophils provide a physiological substrate for ANCA detection in patients with AAV.

Differential detection of nuclear envelope autoantibodies in primary biliary cirrhosis using routine and alternative methods

BackgroundDetection of autoantibodies giving nuclear rim pattern by immunofluorescence (anti-nuclear envelope antibodies - ANEA) in sera from patients with primary biliary cirrhosis (PBC) is a useful tool for the diagnosis and prognosis of the disease. Differences in the prevalence of ANEA in PBC sera so far reported have been attributed to the methodology used for the detection as well as to ethnic/geographical variations. Therefore, we evaluated the prevalence of ANEA in sera of Greek patients with PBC by using methods widely used by clinical laboratories and a combination of techniques and materials.MethodsWe screened 103 sera by immunoblotting on nuclear envelopes and indirect immunofluorescence (IIF) using cells and purified nuclei. Reactivities against specific autoantigens were assessed using purified proteins, ELISA, immunoprecipitation and mass spectrometry.ResultsWe found higher prevalence of ANEA when sera were assayed by IIF on purified nuclei or cultured cells (50%) compared to Hep2 commercially available slides (15%). Anti-gp210 antibodies were identified in 22.3% and 33% of sera using ELISA for the C-terminal of gp210 or both ELISA and immunoprecipitation, respectively. Immunoblotting on nuclear envelopes revealed that immunoreactivity for the 210 kDa zone is related to anti-gp210 antibodies (p < 0.0001). Moreover, we found that sera had antibodies for lamins A (6.8%), B (1%) and C (1%) and LBR (8.7%), whereas none at all had detectable anti-p62 antibodies.ConclusionsThe prevalence of ANEA or anti-gp210 antibodies is under-estimated in PBC sera which are analyzed by conventional commercially available IIF or ELISA, respectively. Therefore, new substrates for IIF and ELISA should be included by clinical laboratories in the analysis of ANEA in autoimmune sera.

Anti-SS-A/Ro antibody determination by indirect immunofluorescence and comparison of different methods of anti-nuclear antibody screening

We evaluated the utility of HEp-2 cells transfected with the 60 kDa SS-A/Ro as a substrate for indirect immunofluorescence (IIF-HEp-2000) to compare several methods for screening Japanese serum samples for anti-SS-A/Ro antibodies. Serum samples from 243 Japanese patients were analyzed by IIF for anti-nuclear antibodies (ANAs), using HEp-2 cells (IIF-HEp-2), and for anti-SS-A/Ro 60 kDa antibodies, using IIF-HEp-2000 and enzyme-linked immunosorbent assay (ELISA). We performed double immunodiffusion and immunoprecipitation experiments, using the products of in vitro transcription and translation, to analyze sera for which there were discrepancies in the results of the IIF-HEp-2000 assay and ELISA. A total of 93 of the 243 serum samples showed findings positive for anti-SS-A/Ro antibodies. Notably, eight of the 93 sera gave positive findings for anti-SS-A/Ro antibodies by IIF-HEp-2000 but ANA-negative by IIF-HEp-2 analysis. Seven sera possessing anti-SS-A/Ro antibodies gave false negative results by IIF-HEp-2000; however, those samples were all ANA positive. ELISA for anti-SS-A/Ro antibodies showed that five and two samples gave false positive and negative results, respectively. Analysis by IIF-HEp-2000 was useful for primary screening of patients for ANAs, especially for anti-SS-A/Ro antibodies; the test could detect anti-SS-A/Ro antibodies not identified on standard substrates in samples obtained from the Japanese population, as reported for the Caucasian population.

Anti-SS-A/Ro antibody determination by indirect immunofluorescence and comparison of different methods of anti-nuclear antibody screening

We evaluated the utility of HEp-2 cells transfected with the 60 kDa SS-A/Ro as a substrate for indirect immunofluorescence (IIF-HEp-2000) to compare several methods for screening Japanese serum samples for anti-SS-A/Ro antibodies. Serum samples from 243 Japanese patients were analyzed by IIF for anti-nuclear antibodies (ANAs), using HEp-2 cells (IIF-HEp-2), and for anti-SS-A/Ro 60 kDa antibodies, using IIF-HEp-2000 and enzyme-linked immunosorbent assay (ELISA). We performed double immunodiffusion and immunoprecipitation experiments, using the products of in vitro transcription and translation, to analyze sera for which there were discrepancies in the results of the IIF-HEp-2000 assay and ELISA. A total of 93 of the 243 serum samples showed findings positive for anti-SS-A/Ro antibodies. Notably, eight of the 93 sera gave positive findings for anti-SS-A/Ro antibodies by IIF-HEp-2000 but ANA-negative by IIF-HEp-2 analysis. Seven sera possessing anti-SS-A/Ro antibodies gave false negative results by IIF-HEp-2000; however, those samples were all ANA positive. ELISA for anti-SS-A/Ro antibodies showed that five and two samples gave false positive and negative results, respectively. Analysis by IIF-HEp-2000 was useful for primary screening of patients for ANAs, especially for anti-SS-A/Ro antibodies; the test could detect anti-SS-A/Ro antibodies not identified on standard substrates in samples obtained from the Japanese population, as reported for the Caucasian population.

Antidesmoplakin antibodies in pemphigus vulgaris

Besides being present in paraneoplastic pemphigus (PNP), circulating antidesmoplakin (DP) antibodies have been found anecdotally in other bullous diseases, including pemphigus foliaceus and pemphigus vulgaris. To verify how frequent anti-DP antibodies are in pemphigus vulgaris. We studied 48 sera from patients with proven pemphigus vulgaris (29 mucosal dominant pemphigus and 19 mucocutaneous pemphigus) by indirect immunofluorescence (IIF) with rat bladder epithelium (RBE) as a substrate and by immunoblotting (IB) on human keratinocyte cultures enriched in DP. Ten sera (21%) were positive in IIF on RBE. By IB, eight sera proved to have antibodies to both DP I (250 kDa) and DP II (210 kDa), one serum had antibodies directed to DP I only, and two sera to DP II only. Our data confirm that RBE is not a specific IIF substrate for the serological diagnosis of PNP. It remains a sensitive and specific substrate for the detection of anti-DP antibodies, which, in patients with pemphigus vulgaris, are probably caused by an epitope-spreading phenomenon.

Comparison of desmoglein ELISA and indirect immunofluorescence using two substrates (monkey oesophagus and normal human skin) in the diagnosis of pemphigus

A prospective study was performed to assess the usefulness of desmoglein enzyme-linked immunosorbent assay testing compared with indirect immunofluorescence in the diagnosis of new cases of pemphigus, as well as to compare the relative sensitivities of monkey oesophagus and normal human skin as substrates for indirect immunofluorescence. These tests were performed on the sera of 29 consecutive new cases of pemphigus diagnosed over a 2-year period based on clinical, histological and direct immunofluorescence findings. Desmoglein enzyme-linked immunosorbent assay was positive in all patients whereas indirect immunofluorescence was positive in only 25 of 29 patients. All four patients with negative indirect immunofluorescence had positive antinuclear antibodies or cytoplasmic fluorescence that could have masked the anti-intercellular antibodies. Desmoglein enzyme-linked immunosorbent assay appeared to reflect the disease activity better than indirect immunofluorescence in a few patients who had active disease of recent onset. Monkey oesophagus was found to be superior or equal to human skin as a substrate for indirect immunofluorescence in both pemphigus vulgaris and foliaceus.

The use of two substrates for indirect immunofluorescence in the diagnosis of pemphigus: reply from authors.

Sir, We thank Jarząbek‐Chorzelska et al. for the interest shown in our paper.1 They concur that two substrates should be used for indirect immunofluorescence (IIF) in order to detect antibodies to both desmoglein (Dsg) 1 and Dsg3 in pemphigus sera. We read with interest that the use of human oesophagus (HO) and guinea‐pig oesophagus (GPO) has proved to be the most sensitive combination of substrates in their experience over many years. In our study, we used a combination of monkey oesophagus (MO) and human skin (HS). The aim of our study was to compare IIF titres on these two substrates in the knowledge not only of the pemphigus subtype, i.e. pemphigus vulgaris (PV) or pemphigus foliaceus (PF), but more specifically the serum content of Dsg1 and Dsg3 antibodies, which were quantitatively measured by enzyme‐linked immunosorbent assay (ELISA). We established that variation in relative titres on these two substrates could be explained by the content of Dsg1 and/or Dsg3 antibodies in sera. HS proved to be more sensitive for detection of Dsg1 antibodies, which are found in all PF sera and approximately 60% of PV sera.2 MO was better for the detection of Dsg3 antibodies which are characteristic of PV. Combining data from both substrates enhanced the overall sensitivity of IIF for PV and PF sera. In addition, the relative titres on each substrate helped differentiate PV and PF.

Rat bladder epithelium: a sensitive substrate for indirect immunofluorescence of bullous pemphigoid.

Serological diagnosis of bullous pemphigoid is based on immunoblotting or indirect immunofluorescence on normal human salt-split skin. These methods are expensive or time-consuming and not available as a routine test in all laboratories. We used rat bladder epithelium as substrate for indirect immunofluorescence and compared it with other substrates and with immunoblotting. Twenty-nine bullous pemphigoid sera were studied on rat bladder epithelium, monkey oesophagus, salt-split skin and with immunoblotting on human keratinocyte cultures. Indirect immunofluorescence on rat bladder epithelium proved to be more sensitive (72%) than on monkey oesophagus alone (45%) and less sensitive than on salt-split skin (97%). Rat bladder epithelium, when tested on 41 sera of a control group, showed a very high specificity: 2/41 (95%). In combination with immunoblotting on keratinocyte extracts, indirect immunofluorescence on rat bladder epithelium allowed 93% of sera to be recognized, a value close to the salt-split skin alone. Rat bladder epithelium appears to be a more sensitive substrate than monkey oesophagus for the diagnosis of bullous pemphigoid and, although less specific, it is easier and faster than using salt-split skin, which remains indispensable to distinguish bullous pemphigoid from epidermolysis bullosa acquisita.

Localization of bullous pemphigoid antibody--an indirect immunofluorescence study of 228 cases using a split-skin technique.

We have re-examined the site of deposition of IgG anti-basement membrane zone antibodies in 228 sera from suspected cases of bullous pemphigoid (BP), using 1.0 M sodium chloride split-skin as substrate for indirect immunofluorescence. Nine sera (4%) produced fluorescence on the floor of the split suggesting sub-basal lamina antibody deposition compatible with a diagnosis of epidermolysis bullosa acquisita (EBA). This ultrastructural localization was confirmed in only three of these nine by immuno-electron microscopy. Clinical details were available on six of these nine cases, and none had clinical features suggesting EBA. We have found the split-skin immunofluorescence technique unhelpful in identifying 'missed' cases of EBA. The prevalence of EBA presenting as BP would appear to be very low indeed in the U.K.

Typing of herpes simplex virus with type-specific human immunoglobulin M in an indirect immunofluorescence assay.

Sera from nine individuals with suspected primary herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2) infection were screened to identify those containing HSV type-specific immunoglobulin M (IgM). Selected sera were then utilized in an IgM-specific indirect immunofluorescent-antibody HSV-typing assay (patent pending). To evaluate the procedure, 29 HSV isolates were grown in cultures of continuous human amnion cells, fixed, and used as substrates for indirect immunofluorescence. Determination of virus type was based on intensity of fluorescence of the substrate with HSV-1- and HSV-2-specific antisera after staining with fluorescein-conjugated anti-human IgM. Typing of the isolates by restriction endonuclease digestion showed that of 29, 18 were HSV-2 and 11 were HSV-1. Results by IgM-specific indirect immunofluorescent-antibody assay were identical to those by restriction endonuclease digestion for 27 of the isolates; 2 isolates failed to replicate adequately in the test cells. The IgM-specific indirect immunofluorescent-antibody procedure appears to be a simple, rapid, and accurate technique which could be of use to clinical virology laboratories.

Identification of cytoskeletal intermediate filaments of vascular endothelial cells as targets for autoantibodies in patient sera

Autoantibodies present in sera of patients suffering from various inflammatory conditions react with fibrillar structures, “microfibrils” (MF), which are abundant in developing fetal connective tissue. The purpose of this study was to further characterize the target antigens and to look for potential antigenic target structures in the adult organism using the indirect immunofluorescence (IFL) technique. Bright vascular endothelial staining was regularly observed in various tissues, e.g., kidneys, skin, and vessels accompanying nerves using anti-MF-positive patient area. A weak staining of the media was seen in arteries. Placental vessels were convenient in vitro targets in a screening assay for anti-MF antibodies. The cytoplasmic structures responsible for the endothelial cell fluorescence were identified using cultured umbilical vein endothelial cells as the IFL substrate. In these cells the fluorescence had the typical perinuclear distribution and fibrillar appearance of cytoskeletal intermediate filaments (IMF). We could further show that anti-IMF and anti-MF autoantibodies gave indistinguishable staining patterns. Some anti- MF IMF -positive sera could be neutralized by “insoluble” placental preparations obtained by procedures for preparation of IMF polypeptides. Immunization with a 50,000-dalton “insoluble” polypeptide produced antibodies with a reactivity similar to that of the autoantibodies. The IFL staining and absorption results were consistent with the ultrastructurally demonstrated large amounts of intermediate filaments in vascular endothelial cells. The results suggest that circulating anti-IMF autoantibodies might be involved in inflammatory reactions in cases of vascular endothelial injury.

Immunopathology of rhino mouse, an autosomal recessive mutant with murine lupus-like disease.

Detection of high incidence of antinuclear antibodies (ANA) was reported in young homozygous rhino mice employing formalinized chicken erythrocyte nuclei as substrate for indirect immunofluorescence (IF) assay. The titers of ANA heightened with increasing age, and attained to 1:1024 by the time mice reached 5 months of age. The occurrence of ANA was associated with development of splenic and hepatic fibrosis, glomerulonephritis and abnormalities of lymphoreticular tissue. The granular deposits of IgG and C3 detected by direct IF were initially found at the basement membrane of dermal‐epidermal junction of rhino mice aged 2.5 months. These deposits distributed progressively in the fibrotic areas of spleen and liver, and renal glomerular tufts at 5 months of age. Dense deposits revealed by electron microscopy were found in the regions where IF of IgG and G3 was observed. Acid buffer eluates from liver and kidney contained IgG reactive with nuclear antigens. Importance of homozygous rhino gene was discussed in relation to development of autoimmune disorders of these mice.