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Chapter 112 : Immunofluorescent Antinuclear Antibody Tests
This chapter reviews the history and the method for antinuclear autoantibodies (ANAs) testing on HEp-2 cells and its utility in a laboratory setting. Antinuclear antibody tests have their origin in the “L.E.” cell phenomenon, which was the observation that neutrophils from patients with systemic lupus erythematosus (SLE) ingested other leukocytes. Widespread commercial production of HEp-2 cells and the development of national quality control schemes ensured that the test entered worldwide routine laboratory usage. The nuclear envelope is the membrane that maintains the integrity of the nucleoplasm during interphase. Important autoantibodies are found against most of the cell cycle-related structures that have been mentioned, such as the centromeres, proliferating cell nuclear antigen, mitotic spindle proteins, and centriole proteins. The pattern on HEp-2 cells is usually sufficient to identify most of these autoantibodies. The majority of laboratories use a non-affinity-purified, fluorescein-conjugated second antibody directed against IgG, -A, and -M heavy chains (or anti-IgG heavy and light chains). The HEp-2 cells should be observed by using an epifluorescence microscope fitted with filters appropriate for fluorescein detection. The largest variation in results reported to quality control schemes relates to differences in fluorescence intensity of the samples. The ANA immunofluorescent HEp-2 test is intended to be used for screening and titration of circulating antinuclear antibodies. Autoantibodies occur in both physiological and pathological conditions.