Binding of established anti-nuclear antibodies to neurons depends on tissue fixation and underlying autoantigens

Lucie Y. Li^1,2,3Markus Höltje⁴Helle Foverskov Rasmussen^2,3Lennard Halle⁵Marie Mayrhofer⁶Martin Blüthner⁶Harald Prüss^2,3*

• ¹Berlin Institute of Health at Charite, Berlin, Germany
• ²Deutsches Zentrum fur Neurodegenerative Erkrankungen Standort Berlin, Berlin, Germany
• ³Charite - Universitatsmedizin Berlin Klinik fur Neurologie mit Experimenteller Neurologie, Berlin, Germany
• ⁴Charite - Universitatsmedizin Berlin Institut fur Integrative Neuroanatomie, Berlin, Germany
• ⁵Helmholtz Zentrum Munchen Institute of Computational Biology, Neuherberg, Germany
• ⁶MVZ Labor PD Dr Volkmann und Kollegen GbR, Karlsruhe, Germany

Anti-nuclear antibodies (ANAs) are central biomarkers in rheumatological conditions and can drive disease pathology. Much less is known about the role of ANAs for neurological symptoms, although some experimental studies demonstrated direct effects on neuronal function, for example in neuropsychiatric lupus erythematosus. Moreover, it is unclear whether ANAs detected in HEp-2 cell-based assays, the gold standard for ANA diagnostics, can also be recognized in modern screening assays for anti-neuronal autoimmunity, such as stainings on rodent brain sections or neuronal cultures. In this study, we therefore conducted a comparative mapping of ANA-positive sera with well-characterized HEp-2 patterns to central nervous system (CNS) tissue, utilizing fixed and unfixed murine brain sections as well as primary murine neurons. We screened 74 ANA-positive sera classified into 14 individual patterns and combinations thereof. Most samples reacted with fixed primary neurons (99%, 73/74 sera), followed by fixed brain sections (93%, 69/74), but much less to unfixed mouse brain (54%, 40/74). While PM/SCL-and RPOI-positive sera showed no binding to unfixed brain sections, U1RNP-and FBLN-ANA reacted strongly across all assays, indicating differences in antigen accessibility. The findings suggest that most ANAs can interact with neural components, which may obscure detection of other anti-neuronal autoantibodies. The here provided foundational mapping of ANA binding in CNS tissue can also facilitate recognition of "CNS-specific ANAs", which bind to neuronal autoantigens but not to HEp-2 cells. Future studies should explore the association with certain neurological manifestations and the role of ANAs for neuronal pathology.