The Jo-1 test is a chemiluminescent immunoassay (CLIA), for use on IDS automated analyzer. It is used for the quantitative determination of the specific IgG antibodies directed against the Jo-1 (histidyl-tRNA synthetase) antigen in human samples of serum or plasma (EDTA).
The extractable nuclear anti-antigen (ENA) autoantibodies represent a large family of non-organ- and non-species-specific autoantibodies, detection of which is of great importance in laboratory diagnosis of systemic rheumatic autoimmune diseases.(1,2,3,4)
From the laboratory point of view, systemic autoimmune diseases are characterized by the presence of anti-nuclear autoantibodies (ANAs). ANA is the first autoantibody test ordered for patients with suspected systemic autoimmune disorders. ANA assays are generally conducted by the indirect immunofluorescence (IFI) technique on a monostrate of HEp-2 cells; IFI positivity for ANA indicates the presence of autoantibodies directed against various nuclear antigens (DNA, histones, non-histonic proteins, nuclear antigens, etc.) or cytoplasmic antigens.(5,6) Significantly high-titer positivity for ANAs should be further investigated via testing for anti-ENA and anti-dsDNA autoantibodies. Positivity for ANAs and for one or more specific tests for anti-ENA and/or anti-dsDNA is highly suggestive of systemic autoimmune disorders: systemic lupus erythematosus (SLE), Sjogren’s Syndrome (SS), progressive systemic sclerosis (PSS), dermatomyositis/polymyositis (DM/PM), and/or mixed connective tissue disease (MCTD).
The Jo-1 antigen is a 55 kDa enzyme found in both the nucleus and the cytoplasm; it has been identified as a histidyl-tRNA synthetase due to the fact that it catalyzes binding of the amino acid histidine with the specific transfer RNA.(7) This antigen is recognized by autoantibodies in the sera of patients affected with dermatopolymyositis, with myositis overlap syndrome, or, more rarely, with other forms of connective tissue disorders.
The frequency of positivity in adult polymyositis is about 30%. Besides histidyl-tRNA synthetase, there are other enzymes of the aminoacyl-tRNA synthetase family(8) the respective autoantibodies of which may be found at positivity percentages less than those of the anti-Jo-1 antibodies in patients with dermatopolymyositis (anti-PL7, anti-PL12, anti-OJ, anti-EJ, anti-SC, anti-KS). The presence of anti-Jo-1 antibodies and/or antibodies against other synthetases configures antisynthetase syndrome, characterized by acute onset, pulmonary interstitial disease, inflammatory muscle disease, fever, polyarthtitis, and Raynaud’s phenomenon.(9,10,11) The prognosis for this syndrome is correlated with the presence of pulmonary interstitial disease.(12)
- CA von Mühlen, EM Tan. Autoantibodies in the diagnosis of systemic rheumatic diseases. Sem Arthr Rheum 1995; 24: 323-58.
- RL Humbel. Auto-immunité, auto-anticorps et maladie. In : Humbel RL, ed. Autoanticorps et maladies autoimmunes, Paris, France : Edition Scientifiques Elsevier; 1997: 17-20.
- PN Hollingsworth, SC Pummer, RL Dawkins. Antinuclear antibodies. In : Peter JB, Shoenfeld Y, eds. Autoantibodies. Amsterdam, The Netherlands : Elsevier Science BV; 1996: 74-90.
- CA Slater, RB Davis, RH Shmerling. Antinuclear antibodies testing. A study of clinical utility. Arch Int Med 1996; 156: 1421-5.
- RL Humbel. Detection of antinuclear antibodies by immunofluorescence. In : van Venrooij, Maini RN eds. Manual of Biological Markers of Disease. Dordrecht, The Netherlands : Kluwer; 1993: A2:1-16.
- National Committee for Clinical Laboratory Standardization. Quality assurance for the indirect immunofluorescence test for autoantibodies to nuclear antigen ( IF-ANA ). Approved Guideline. Wayne, PA: NCCLS I/LA2-A, vol. 16 ( 11 ); 1996.
- K Conrad, W Schöbler, F Hiepe. Jo-1 autoantibodies. In : Autoantibodies in systemic autoimmune diseases : A diagnostic reference. Lengerich : PABST 2002; pp. 92-3.
- R Brouwer, GJ Hengstman, W Vree Egberts, H Ehrfeld, B Bozic, A Ghirardello, et al. Autoantibodies profiles in the sera of European patients with myositis. Ann Rheum Dis 2001; 60: 116-23.
- GJ Hengstman, BG van Engelen, WT Vree Egberts, WJ van Venrooij. Myositis-specific autoantibodies: overview and recent developments. Curr Opin Rheumatol 2001; 13: 476-82.
- A Imbert-Masseau, M Hamidou, C Agard, JY Grolleau, P Cherin. Antisynthetase syndrome. Joint Bone Spine 2003; 70: 161-8.
- IN Targoff. Laboratory testing in the diagnosis and management of idiopathic inflammatory myopathies. Rheum Dis Clin North Am 2002; 28: 859-90.
- RM Bernstein, SH Morgan, J Chapman, CC Bunn, MB Mathews, M Tner-Warwick, et al. Anti Jo1 antibody: a marker for myositis with interstitial lung disease. Br M J 1984; 289: 151-2.