Fig. 1.

Images are of 16 μm paraformaldehyde (4%) fixed sagittal cryosections of mouse hippocampus. Immunohistochemistry was performed using cerebrospinal fluid (CSF) diluted 1:4 to detect anti-neuronal antibodies (green; cell nuclei marker DAPI is blue). A: CSF from a patient with COVID-19 associated acute necrotizing encephalopathy where neuropil staining is found in the subiculum, stratum oriens and stratum radiatum in all cornu ammonis (CA) subfields, dentate gyrus polymorph layer and faint in the molecular layer. The pyramidal layer of CA1 and stratum lancosum-moleculare are both negative. B: CSF from a patient presenting with COVID-19 associated acute hemorrhagic leukoencephalitis. In the hippocampus and the cortex (see top left corner) there is a general dendritic staining. Staining can also be observed in some specific cell somas, especially in the subiculum and cortex (not shown). The signal is fainter in the CA1 stratum oriens, CA1 stratum lancosum and the dentate gyrus polymorph layer compared to the rest of the area. C: CSF from patient with COVID-19 associated malignant catatonia shows membrane staining of cells in the pyramidal layer, subiculum and granule cell layer of the dentate gyrus. D: Reference CSF sample, from a donor with bipolar disease without suspected autoimmunity.