Jo-1 Ab in serum

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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.

Indications

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

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

Table

value 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

More specific terms

Additional terms

Component of

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.
  5. Panel of 8 tests Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0051668.jsp
  6. Jo-1 (Histidyl-tRNA Synthetase) Ab, IgG Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0099592.jsp
  7. 7.0 7.1 Medical Knowledge Self Assessment Program (MKSAP) 17, 18. American College of Physicians, Philadelphia 2015, 2018