In 1948, Malcolm Hargraves, Helen Richmond, and Robert Morton during evaluation of bone marrow examinations at the Mayo Clinic (Minnesota, USA) observed exclusively in patients with systemic lupus erythematosus (SLE) the presence of abnormal cells with specific morphology (the nucleus is phagocytosed by mature leucocytes) and introduced the term "LE cell" 1 . Although LE cells are usually found in the bone borrow of these patients, it has been shown that after a period of incubation they can be formed in buffy coats of peripheral blood 2 indicating that the LE phenomenon is rather a secondary response to a blood circulating factor and not a developmental cellular defect.One year later, two research laboratories independently confirmed the inducible nature of LE phenomenon 3 . Incubation of bone marrow cells from healthy subject with plasma from SLE patients lead to the formation of LE cells. It took almost a decade and a series of ingenious research to discover that the phenomenon LE cells are autoantibodies that bind to nuclear elements. The molecular nature of the LE factor was determined when it was discovered that this factor lies in the gamma globulin fraction 4 . The nuclear specificity has been shown later by at least two different research groups at the same time. Holborow et al, showed that in all tissues examined (skin, heart muscle, kidney, thyroid and spleen) exposure of the section to LE cells positive sera resulted in marked specific fluorescence of the nuclei on subsequent staining with the anti-globulin conjugate 5 .In the same year, Holman and Kunkel published a seminal work in Science where they show that the LE serum factor possesses affinity for cell nuclei and nucleoproteins 6 . One year later, Friou and colleagues introduced an indirect immunofluorescence (IIF) assay with end-point titres for the detection of anti-nuclear antibodies 7,8 (ANA). Subsequently, three distinct classic patterns (homogeneous, speckled and nucleolar) of ANA fluorescence were described by Swanson Beck during the staining of rat liver sections with patients' serum 9 , introducing the importance of ANA pattern in clinical practice. Since then significant progress has been made on the identification of ANA specificity in SLE and other systemic autoimmune rheumatic diseases, including Rheumatoid Arthritis (RA), Sjögren's Syndrome (SjS), Systemic Sclerosis (SSc), Mixed Connective Tissue Disease (MCTD), and Idiopathic Inflammatory Myopathies (IIM).
AbstractThe antinuclear antibody (ANA) testing is an indispensable diagnostic tool for the management of systemic autoimmune rheumatic diseases (SARD). From the initial discovery of ANA identification until today there has been considerable technical progress in ANA testing and standardisation which has allow the development of commercial ANA assay kits that are widespread used in clinical and research practice. In this mini-review we explore the history and recent advancements in ANA testing and provide guidelines to the laboratory interpretation and clinical assessment of ANA...