CLINICAL AND IMMUNOHISTOCHEMICAL COMPARISON OF IN-VIVO INJECTED ANTI-HU AND CONTROL IGG IN THE NERVOUS-SYSTEM OF THE MOUSE

Anti-Hu antibodies are usually present in patients with paraneoplastic encephalomyelitis/sensory neuropathy (PEM/SN), and anti-su IgG is fou nd in the nucleus of neurons in the autopsy of these patients. To inve stigate the clinical effect and distribution of anti-au IgG in the ner vous system in an experimental animal model, we injected intraperitone ally anti-au IgG from five patients with PEM/SN to mice daily for 1 or 2 weeks. The IBG distribution in the nervous system was analyzed by a n avidin-biotin immunoperoxidase technique in animals sacrificed 24 h after the last injection. In one group of mice the nervous system was fixed by perfusion and in another (autopsy group) by immersion after k eeping the dead animal 16 h at 4 degrees C. None of the mice showed cl inical or pathological abnormalities. IgG immunoreactivity was similar in the nervous system of mice injected with anti-au or control IgG. I n the perfusion-fixed mice, IBG was present in leptomeninges, choroid plexus and extracellular space of Gasserian and dorsal root ganglia (D RG). In the autopsy group, there was Ige immunoreactivity in the cytop lasm of neurons of many areas of the brain and in more than 90% of neu rons of DRG. Neuronal nuclear IgG deposits were only rarely observed. We conclude that anti-su antibodies alone probably are not responsible for the PEM/SN syndrome. IgG diffusion into the cytoplasm of neurons is a post-mortem artifact, but this model did not reproduce the predom inant nuclear IgG staining observed in autopsies from PEM/SN patients.