Autoantibodies against the autophagic protein microtubule-associated light-chain 3 (LC3): Immunocharacterization of an atypical ANA pattern

• Published in: Autoimmunity (Chur, Switzerland) Vol. 53; no. 5; pp. 245 - 252
• Main Authors: Maellaro, Emilia, Terzuoli, Lucia, Bacarelli, Maria Romana, Del Bello, Barbara, Bizzaro, Nicola, Porcelli, Brunetta
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 03-07-2020; Taylor & Francis Group
• Subjects: ANA patterns; antinuclear antibodies (ANA); Autoantibodies; autophagy; microtubule-associated light-chain 3 protein (LC3); antinuclear antibodies (ANA); Autoantibodies; autophagy; microtubule-associated light-chain 3 protein (LC3); ANA patterns
• ISSN: 0891-6934; 1607-842X
• DOI: 10.1080/08916934.2020.1755963

Autoantibodies to nuclear and cytoplasmic antigens are commonly detected by indirect immunofluorescence (IIF) on HEp-2 cells, and three major staining patterns (nuclear, cytoplasmic, and mitotic) are distinguished. Here, we report an atypical cytoplasmic pattern, not described so far, observed in the serum of a patient with a controversial diagnosis of systemic lupus erythematosus (SLE). Moreover, for the first time, we have revealed the presence of autoantibodies against the microtubule-associated light-chain 3 (LC3) protein, which plays a key role in the autophagic process. The target antigen has been identified in IIF by means of a competition test using purified anti-LC3 antibodies on HEp-2 cells, and confirmed by Western blot analysis using cellular or recombinant LC3 as antigen, immunoreacted with the patient's serum. The identification of this atypical pattern and the related autoantibody-antigen system sheds new light on autophagy, which is increasingly considered to be involved in the etiopathogenesis of autoimmune disorders, and could contribute to select more personalized therapies.