Anti Jo1 In Serum

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Contents 1 Introduction 2 Etiology 3 Reference-interval 4 Principle 5 Clinical-significance 6 Specimen 7 Interpretation 8 More General Terms 9 Additional Terms 10 References

Introduction

• Anti Jo-1
  

• In some settings, appears under anti-nuclear antibodies ( ANA). Antinuclear antibody picks up anti Jo-1 (although technically histidyl-t- RNA synthetase is a cytoplasmic antigen.

Etiology

• polymyositis (30%)

Reference-interval

• Normal: Negative

Principle

• Jo-1 antigen is purified from calf thymus, bound to microwells & stabilized for extended shelf life. Diluted patient sera are placed in the microwells & incubated. If anti-Jo-1 antibodies are present, they will bind to the antigen in the microwell. After washing the microwells to remove residual sample, a second incubation with anti-human IgG conjugated to alkaline phosphatase is carried out. Conjugate will bind immunologically to the anti- Jo-1 IgG of the antigen- antibody complex, forming a 'sandwich' consisting of:
  
• Conjugate (Enzyme-labeled Anti-human IgG)
• Human anti-Jo-1 ( IgG)
• Well Coated with Jo-1 antigen
  
• Unbound conjugate is removed in the subsequent washing step. Enzyme substrate is then added to the microwell & if bound conjugate is present, the colorless substrate (p-nitrophenyl phosphate) will be hydrolyzed to form a yellow end product ( p-nitrophenol). The intensity of the color is measured photometrically at 405 nm & is proportional to the concentration of anti-Jo-1 present in the patients sample.

Clinical-significance

• anti-Jo-1 antibody is an autoantibody directed at the cellular enzyme histidyl-t- RNA synthetase
• it is present in ~30% of patients with polymyositis ( PM)
• it is more uncommon in dermatomyositis ( DM) patients & rare in other connective tissue diseases
• antibody to Jo-1 appears to be not only a marker for PM but also defines a subgroup of myositis patients with an increased frequency of interstitial pulmonary disease; these patients may represent a subgroup with polymyositis- systemic sclerosis overlap
• there is evidence that anti-Jo-1 antibody titers may fluctuate in concordance with myositis activity & it has been suggested that the better quantification obtainable by the ELISA method will be useful adjunct in the clinical evaluation of such patients.

Specimen

• Serum is separated from the clot & refrigerated, 2-8 degrees C for short term storage or stored frozen, -20 degrees C, for long term storage. Avoid freeze-thaw cycles. CAUTION: Serum samples should not be heat inactivated, as this may cause false positive results.
  
• No special patient preparation required.

Interpretation

*     <20 EU/mL:    negative for antibodies to Jo-1. 
*     20-25 EU/mL:  Equivocal for antibodies to Jo-1. 
*     >25 EU/mL:    positive for antibodies Jo-1

More General Terms

• serology

Additional Terms

• exosome complex exonuclease RRP45 (polymyositis/scleroderma autoantigen 1, autoantigen PM/Scl 1, polymyositis/scleroderma autoantigen 75 kD, PM/Scl-75, P75 polymyositis-scleroderma overlap syndrome associated autoantigen, EXOSC9, PMSCL1)
• histidyl tRNA synthetase; histidine-tRNA ligase; HisRS (HARS, HRS)

References

1. Henry, John Bernard, Clinical Diagnosis amd Management by Labortory Methods, W. B. Saunders Co., Philadelphia, 1991. pp 891-892.
2. The Physicians Guide to ENA Testing, Diamedix Corporation, Miami, 1991. pp 1-8.
3. Summary of Procedure. DiaMedix Corporation, Miami, Oct. 1991. pp 1-8.
4. Poly-ENA Extractable Nuclear Antigen Assay For Detection Of Antibodies to RNP, Sm, and/or SSA (RO), & SSB (LA). Zeus Scientific, Inc., Raritan, New Jersey, 1987. pp 1-5.

anti-Jo-1 in serum