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.

通常通过间接免疫荧光（IIF）在HEp-2细胞上检测到针对核和细胞质抗原的自身抗体，并区分了三种主要的染色模式（核，细胞质和有丝分裂）。在此，我们报告了在有系统诊断性系统性红斑狼疮（SLE）的有争议诊断的患者血清中观察到的一种非典型细胞质模式，到目前为止尚未描述。此外，我们首次揭示了针对微管相关轻链3（LC3）蛋白的自身抗体的存在，该蛋白在自噬过程中起关键作用。通过使用纯化的抗LC3抗体对HEp-2细胞进行竞争试验，在IIF中鉴定了目标抗原，并使用细胞或重组LC3作为抗原与患者血清进行了免疫反应，通过Western blot分析确认了目标抗原。