Jo-1 Ab in serum
Introduction
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)
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
- 20-30% sensitivity for polymyositis
- 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
- associated with anti-synthetase syndrome[7]
- 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
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
- anti-Jo-1
- 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)
Component of
References
- ↑ Henry, John Bernard, Clinical Diagnosis amd Management by Labortory Methods, W. B. Saunders Co., Philadelphia, 1991. pp 891-892.
- ↑ The Physicians Guide to ENA Testing, Diamedix Corporation, Miami, 1991. pp 1-8.
- ↑ Summary of Procedure. DiaMedix Corporation, Miami, Oct. 1991. pp 1-8.
- ↑ 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.
- ↑ Panel of 8 tests Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0051668.jsp
- ↑ Jo-1 (Histidyl-tRNA Synthetase) Ab, IgG Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0099592.jsp
- ↑ 7.0 7.1 Medical Knowledge Self Assessment Program (MKSAP) 17, 18. American College of Physicians, Philadelphia 2015, 2018