Case Report of Neuron-Binding IgGs in ALS Patient Serum in Argentina

Abstract

Our previous studies demonstrated that motor nerve terminals are a target for autoimmune response, induced by immunoglobulin’s (IgGs) from sporadic ALS patients, resulting in neuromuscular dysfunction in vivo [3]. Indeed, IgGs obtained from patients with ALS reduce Ca 2+ transients and glutamate receptor desensitization so that excitotoxic damage is facilitated in a culture brain neuron model [4]. Furthermore, we have shown that subcutaneous injection of ALS-IgG into the levator auris muscle were immunoreactive to spinal motoneurons, preferentially accumulate in the soma by binding to unknown specific cytoplasmic targets [5]. The question then arises about the role of ALS serum factors on spinal cord neurons and the inflammatory process that would be associated with the disease onset and development. In vitro spinal cord preparations have been exploited as a model to investigate early pathophysiological mechanisms of spinal cord damage and developmental changes in cellular profiles [6]. The aim of the present study was to investigate, using neonatal mouse spinal cord preparations in vitro , the effect of serum from sporadic ALS patients. Thus, sera from patients with sporadic ALS diagnosis in accordance with the El Escorial criteria [7] and from healthy volunteer subjects were tested on neuronal numbers and microglia morphology. Abstract Amyotrophic Lateral Sclerosis (ALS) is a degenerative disorder characterized by ongoing loss of motoneurons. The etiology of the sporadic ALS form it is thought to be related to immune-mediated motoneuron degeneration and death. The present study was designed to describe the effect of serum factors derived from sporadic ALS patients on mouse spinal cord preparations in vitro. Sera from patients with sporadic ALS were collected and used for immunofluorescence analysis to investigate their effects on neuronal survival and microgliosis. Our experiments demonstrated that 5 h application of serum factors (derived from three ALS patients) labeled with human IgG secondary antibody were localized to ventral spinal neurons identified with the NeuN marker. Moreover, a significant reduction in the number of ventral NeuN positive cells was observed with serum from a patient who suffered from upper motor neuron signs as criteria for ALS diagnosis (20% less compared to sham, spinal cord preparations without serum). No change in microglia number was found after exposure to ALS sera, although in two cases a significant decrease in microglial branch length was observed (28-32%). Microglia morphology showed increased number of end points and branches with serum from the patient with upper motor neuron symptoms. These observations were absent after control sera. Our data indicate that spinal cord cultures can be a useful model to further characterize the pathological processes of sporadic ALS and the immune mechanism as previously suggested in vivo . Future studies are needed to unveil the molecular mechanisms underlying this preferential targeting of neurons and microglia by ALS serum.