Abstract Details

Anti-Ma2 antibodies are paraneoplastic autoantibodies associated with syndromes of limbic, diencephalic, and brainstem encephalitis in patients with testicular or other neoplasms.  The role of anti-Ma2 antibodies in neuronal injury has not been defined, nor is it known whether these antibodies interact with their intracellular antigenic targets in living neurons.  We have previously demonstrated that both anti-Yo and anti-Hu antibodies are taken up by neurons in rat organotypic brain cultures and that intracellular binding of these antibodies is followed by cell death.  Here we examined whether neuronal uptake and cytotoxicity of anti-Ma2 antibodies in vitro affected brain regions involved in clinical disease.

To determine the effect of paraneoplastic anti-Ma2 antibodies on neurons in organotypic rat brain cultures.

Organotypic cultures of rat hippocampus, brainstem and cerebellum, were incubated with sera or cerebrospinal fluid (CSF) from 5 anti-Ma2 positive patients for intervals of up to 144 hours.  Dispersed cortical neuronal cultures were also studied.  Neuronal viability was determined using SYTOX dead cell staining.  Cultures were then fixed, permeabilized, stained with Cy-5 conjugated anti-human IgG, and studied using confocal microscopy.

Anti-Ma2 antibodies were taken up by neurons in hippocampus and brainstem and accumulated in cytoplasm, nuclei, and granular structures in both cytoplasm and neuronal processes.  A fraction of the granular structures labeled with anti-Ma2 antibodies co-labeled with antibodies to the RNA-binding protein, Staufen.  Antibody uptake was associated with scattered neuronal death over the period of time studied.  Uptake of anti-Ma2 by Purkinje or other cerebellar neurons was rarely observed. 

Anti-Ma2 antibody was taken up by neurons in hippocampus and brainstem, followed by scattered neuronal death.  The distribution of antibody uptake and neuronal injury differed from that seen with anti-Yo and anti-Hu antibodies and corresponded to the syndromes of clinical illness seen in human patients.  Anti-Ma2 antibody may play a direct role in neuronal injury.