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Concept: Immunofluorescence

25

Anti-neutrophil cytoplasmic antibodies (ANCAs) are valuable laboratory markers used for the diagnosis of well-defined types of small-vessel vasculitis, including granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). According to the 1999 international consensus on ANCA testing, indirect immunofluorescence (IIF) should be used to screen for ANCAs, and samples containing ANCAs should then be tested by immunoassays for proteinase 3 (PR3)-ANCAs and myeloperoxidase (MPO)-ANCAs. The distinction between PR3-ANCAs and MPO-ANCAs has important clinical and pathogenic implications. As dependable immunoassays for PR3-ANCAs and MPO-ANCAs have become broadly available, there is increasing international agreement that high-quality immunoassays are the preferred screening method for the diagnosis of ANCA-associated vasculitis. The present Consensus Statement proposes that high-quality immunoassays can be used as the primary screening method for patients suspected of having the ANCA-associated vaculitides GPA and MPA without the categorical need for IIF, and presents and discusses evidence to support this recommendation.

Concepts: Present, Protease, Wegener's granulomatosis, Pascal, Immunofluorescence, Myeloperoxidase, Anti-neutrophil cytoplasmic antibody, Proteinase 3

6

Anti-nuclear antibodies (ANA) are fundamental for the diagnosis of autoimmune diseases, and have been determined by indirect immunofluorescence assay (IIFA) for decades. As the demand for ANA testing increased, alternative techniques were developed challenging the classic IIFA. These alternative platforms differ in their antigen profiles, sensitivity and specificity, raising uncertainties regarding standardisation and interpretation of incongruent results. Therefore, an international group of experts has created recommendations for ANA testing by different methods.Two groups of experts participated in this initiative. The European autoimmunity standardization initiative representing 15 European countries and the International Union of Immunologic Societies/World Health Organization/Arthritis Foundation/Centers for Disease Control and Prevention autoantibody standardising committee. A three-step process followed by a Delphi exercise with closed voting was applied.Twenty-five recommendations for determining ANA (1-13), anti-double stranded DNA antibodies (14-18), specific antibodies (19-23) and validation of methods (24-25) were created. Significant differences between experts were observed regarding recommendations 24-25 (p<0.03). Here, we formulated recommendations for the assessment and interpretation of ANA and associated antibodies. Notably, the roles of IIFA as a reference method, and the importance of defining nuclear and cytoplasmic staining, were emphasised, while the need to incorporate alternative automated methods was acknowledged. Various approaches to overcome discrepancies between methods were suggested of which an improved bench-to-bedside communication is of the utmost importance. These recommendations are based on current knowledge and can enable harmonisation of local algorithms for testing and evaluation of ANA and related autoantibodies. Last but not least, new more appropriate terminologies have been suggested.

Concepts: Immune system, Antibody, Positive predictive value, Type I and type II errors, Sensitivity and specificity, Immunology, Autoimmune diseases, Immunofluorescence

5

We studied antibody response in 9 healthcare workers in Jeddah, Saudi Arabia, who survived Middle East respiratory syndrome, by using serial ELISA and indirect immunofluorescence assay testing. Among patients who had experienced severe pneumonia, antibody was detected for >18 months after infection. Antibody longevity was more variable in patients who had experienced milder disease.

Concepts: Antibody, Saudi Arabia, Arabian Peninsula, Riyadh, United Arab Emirates, Middle East, Immunofluorescence, Jordan

4

A 56-year-old female with adult-onset asthma was admitted to the cardiology service with intermittent left-sided chest pain and progressive dyspnoea. Twelve months prior to this admission, she had received a course of prednisolone for bilateral anterior uveitis. Physical examination was unremarkable with blood sampling revealing a marked eosinophilia (eosinophil count 17.3×10(9)/L) and a perinuclear antineutrophil cytoplasmic antibody staining pattern on indirect immunofluorescence microscopy (myeloperoxidase antibodies 83 IU/mL). ECG demonstrated anterolateral T-wave inversion (see online supplementary figure S1). High-sensitivity troponin T was elevated at 100 ng/L. Invasive coronary angiography showed unobstructed coronary arteries. Echocardiography and cardiac magnetic resonance (CMR) were performed (figure 1).

Concepts: Antibody, Blood, Myocardial infarction, Atherosclerosis, Cardiology, Heart, Atheroma, Immunofluorescence

1

Single-molecule-based super-resolution microscopy offers researchers a unique opportunity to quantify protein copy number with nanoscale resolution. However, while fluorescent proteins have been characterized for quantitative imaging using calibration standards, similar calibration tools for immunofluorescence with small organic fluorophores are lacking. Here we show that DNA origami, in combination with GFP antibodies, is a versatile platform for calibrating fluorophore and antibody labeling efficiency to quantify protein copy number in cellular contexts using super-resolution microscopy.

Concepts: Antibody, DNA, Protein, Gene, Molecular biology, Green fluorescent protein, Microscopy, Immunofluorescence

1

Onconeural antibodies are associated with cancer and paraneoplastic encephalitis. While their pathogenic role is still largely unknown, their high diagnostic value is undisputed. In this study we describe the discovery of a novel target of autoimmunity in an index case of paraneoplastic encephalitis associated with urogenital cancer.A 75-year-old man with a history of invasive bladder carcinoma 6 years ago with multiple recurrences and a newly discovered renal cell carcinoma presented with seizures and progressive cognitive decline followed by super-refractory status epilepticus. Clinical and ancillary findings including brain biopsy suggested paraneoplastic encephalitis. Immunohistochemistry of the brain biopsy was used to characterize the inflammatory response. Indirect immunofluorescence assay (IFA) was used for autoantibody screening. The autoantigen was identified by histo-immunoprecipitation and mass spectrometry and was validated by expressing the recombinant antigen in HEK293 cells and neutralization tests. Sera from 125 control patients were screened using IFA to test for the novel autoantibodies.IFA analysis of serum revealed a novel autoantibody against brain tissue. An intracellular enzyme, Rho-associated protein kinase 2 (ROCK2), was identified as target-antigen. ROCK2 was expressed in affected brain tissue and archival bladder tumor samples of this patient. Brain histopathology revealed appositions of cytotoxic CD8(+) T cells on ROCK2-positive neurons. ROCK2 antibodies were not found in the sera of 20 patients with bladder cancer and 17 with renal cancer, both without neurological symptoms, 49 healthy controls, and 39 patients with other antineuronal autoantibodies. In conclusion, novel onconeural antibodies targeting ROCK2 are associated with paraneoplastic encephalitis and should be screened for when paraneoplastic neurological syndromes, especially in patients with urogenital cancers, occur.

Concepts: Immune system, Antibody, Cancer, Brain, Anatomical pathology, Neurology, Bladder cancer, Immunofluorescence

1

Single-molecule localization microscopy (SMLM) image quality and resolution strongly depend on the photoswitching properties of fluorophores used for sample labeling. Development of fluorophores with optimized photoswitching will considerably improve SMLM spatial and spectral resolution. Currently, evaluating fluorophore photoswitching requires protein-conjugation before assessment mandating specific fluorophore functionality, which is a major hurdle for systematic characterization. Herein, we validated polyvinyl alcohol (PVA) as a single-molecule environment to efficiently quantify the photoswitching properties of fluorophores and identified photoswitching properties predictive of quality SMLM images. We demonstrated that the same fluorophore photoswitching properties measured in PVA films and using antibody adsorption, a protein-conjugation environment analogous to labeled cells, were significantly correlated to microtubule width and continuity, surrogate measures of SMLM image quality. Defining PVA as a fluorophore photoswitching screening platform will facilitate SMLM fluorophore development and optimal image buffer assessment through facile and accurate photoswitching property characterization, which translates to SMLM fluorophore imaging performance.

Concepts: Scientific method, Evaluation, Immunohistochemistry, Fluorescein, IMAGE, Immunofluorescence, Polyvinyl alcohol, Polyvinyl acetate

1

To determine sensitivity and specificity of a standardized recombinant cell-based indirect immunofluorescence assay (RC-IFA) for anti-Tr antibodies in comparison to a reference procedure.

Concepts: Type I and type II errors, Sensitivity and specificity, Immunofluorescence

1

We assessed the diagnostic accuracy of two immunochromatographic tests (ICTs), the Access Bio CareStart Scrub Typhus test (Somerset, NJ) (IgM), and the SD BIOLINE Tsutsugamushi test (Kyonggi-do, Republic of Korea) (IgG, IgM, or IgA) compared with indirect immunofluorescence assay (IFA) and real-time PCR results as reference tests using 86 paired acute and convalescent specimens from febrile patients. The sensitivity and specificity of the CareStart test were 23.3% (95% confidence interval [CI]: 11.8-38.6) and 81.4% (95% CI: 66.6-91.6), respectively, for acute specimens and 32.6% (95% CI: 19.1-48.5) and 79.1% (95% CI: 64.0-90.0), respectively, for convalescent specimens. For the SD BIOLINE test, sensitivity and specificity were 20.9% (95% CI: 10.0-36.0) and 74.4% (95% CI: 58.8-86.5), respectively, for acute specimens and 76.7% (95% CI: 61.4-88.2) and 76.7% (95% CI: 61.4-88.2), respectively, for convalescent specimens. The poor sensitivity obtained for both ICTs during this study when performed on acute specimens highlights the difficulties in prompt diagnosis of scrub typhus.

Concepts: Type I and type II errors, Sensitivity and specificity, Immunofluorescence, Scrub typhus

1

: Skin biopsy for direct immunofluorescence (DIF) testing is an essential tool in the diagnosis of blistering diseases. In the majority of cases, positive epidermal immunofluorescent staining is indicative of an autoimmune bullous disease (AIBD). We identified 2 patients with bullous dermatophyte infection diagnosed on hematoxylin- and eosin-stained sections who had positive DIF findings on biopsy of perilesional skin. We subsequently reviewed the literature regarding positive DIF findings in conditions other than AIBD. Other infections, including herpesviridae, scabies, and orf, have rarely been reported to yield positive DIF findings, with positive staining at the dermoepidermal junction. Some genodermatoses and many inflammatory skin diseases, including lichen planus, psoriasis, graft-versus-host disease, among others, may also have DIF findings mimicking those of both intra- and subepidermal AIBD. Although rare, positive DIF results occur in conditions other than AIBD. In many instances, the pathophysiological mechanisms behind immunoreactant deposition in these conditions are poorly understood. Misleading DIF results may lead to delay in correct diagnosis and treatment. Clinicians should be aware of potential alternate sources of positivity when there is lack of clinical correlation with immunofluorescence findings.

Concepts: Inflammation, Cancer, Disease, Infectious disease, Medical terms, Poverty, Infection, Immunofluorescence