AC-1 - Nuclear homogeneous
Previous Nomenclature Diffuse
Description Homogeneous and regular fluorescence across all nucleoplasm. The nucleoli maybe stained or not stained depending on cell substrate. Mitotic cells (metaphase, anaphase, and telophase) have the chromatin mass intensely stained in a homogeneous hyaline fashion.
Antigen Association dsDNA, nucleosomes, histones
Clinical Relevance
First level information
About Clinical Relevance & List of Abbreviations

Found in patients with SLE, chronic autoimmune hepatitis or juvenile idiopathic arthritis

If SLE is clinically suspected, it is recommended to perform a follow-up test for anti-dsDNA antibodies, alone or in combination with dsDNA/histone complexes (nucleosomes/chromatin); anti-dsDNA antibodies are included in the classification criteria for SLE (15, 16)

If chronic autoimmune hepatitis or juvenile idiopathic arthritis is suspected, follow-up testing is not recommended because the respective autoantigens revealing the AC-1 pattern are not completely defined (17)

Notes: Although autoantibodies to Topoisomerase I (formerly Scl-70) may be reported as nuclear homogeneous, they typically reveal a composite AC-29 HEp-2 IIFA pattern; as such, clinical suspicion of SSc may warrant follow-up testing for reactivity to this antigen (14, 18)
Although AC-1 is the most prevalent pattern in chronic autoimmune hepatitis, other HEp-2 IIFA patterns may occur, but also for these patterns the autoantigens are not completely defined (19)
First level information references
Andrade LEC, Klotz W, Herold M, et al. International consensus on antinuclear antibody patterns: definition of the ac-29 pattern associated with antibodies to DNA topoisomerase I. Clin Chem Lab Med 2018;56:1783-8.
Conrad K, Schössler W, Hiepe F. Autoantibodies in systemic autoimmune diseases: a diagnostic reference. 2. 3th edn. Autoantigens autoantibodies autoimmunity, 2015.
Petri M, Orbai AM, Alarcón GS, et al. Derivation and validation of the systemic lupus international collaborating clinics classification criteria for systemic lupus erythematosus. Arthritis Rheum 2012;64:2677-86.
Conrad K, Schössler W, Hiepe F. Autoantibodies in organ specific autoimmune diseases. a diagnostic reference. 8. 2th edn. Autoantigens autoantibodies autoimmunity, 2017.
Dellavance A, Gallindo C, Soares MG, et al. Redefining the Scl-70 indirect immunofluorescence pattern: autoantibodies to DNA topoisomerase I yield a specific compound immunofluorescence pattern. Rheumatology 2009;48:632-7.
European Association for the Study of the Liver. EASL clinical practice guidelines: autoimmune hepatitis. J Hepatol 2015;63:971-1004.
Second level information
Second level information references

How best to recognize the metaphase plate?
Question: As a new person learning HEp-2 IFA, is there any good tip to identify whether the metaphase plate is positive or negative?

Low titer anti-dsDNA serum negative by HEp-2 IFA?
Question: Can I have a negative HEp-2 IFA result in a sample with positive Crithidia assay at 1/20? The negative HEp-2 IFA was confirmed with slides from different commercial brands.
Online since 19 May 2015