Lymphocyte subset abnormalities in patients with spasmodic torticollis

Exploration of potential immune mechanisms in cervical dystonia

BACKGROUND

Although there are many possible causes for cervical dystonia (CD), a specific etiology cannot be identified in most cases. Prior studies have suggested a relationship between autoimmune disease and some cases of CD, pointing to possible immunological mechanisms.

OBJECTIVE

The goal was to explore the potential role of multiple different immunological mechanisms in CD.

METHODS

First, a broad screening test compared neuronal antibodies in controls and CD. Second, unbiased blood plasma proteomics provided a broad screen for potential biologic differences between controls and CD. Third, a multiplex immunoassay compared 37 markers associated with immunological processes in controls and CD. Fourth, relative immune cell frequencies were investigated in blood samples of controls and CD. Finally, sequencing studies investigated the association of HLA DQB1 and DRB1 alleles in controls versus CD.

RESULTS

Screens for anti-neuronal antibodies did not reveal any obvious abnormalities. Plasma proteomics pointed towards certain abnormalities of immune mechanisms, and the multiplex assay pointed more specifically towards abnormalities in T lymphocytes. Abnormal immune cell frequencies were identified for some CD cases, and these cases clustered together as a potential subgroup. Studies of HLA alleles indicated a possible association between CD and DRB1*15:03, which is reported to mediate the penetrance of autoimmune disorders.

CONCLUSIONS

Altogether, the association of CD with multiple different blood-based immune measures point to abnormalities in cell-mediated immunity that may play a pathogenic role for a subgroup of individuals with CD.

The Dystonias

Dystonia is a difficult problem for both the clinician and the scientist. It is sufficiently common to be seen by almost all physicians, yet uncommon enough to prevent any physician from gaining broad experience in its diagnosis and treatment. Each case represents a difficult challenge even to the specialist. The basic scientist is faced with investigating a disorder that is without relevant animal models and which is so rare that obtaining suitable tissue for study is a major obstacle. Dystonia may be idiopathic, or associated with lesions from many sources, including a variety of rare diseases. If idiopathic, it may be genetically transmitted or sporadic. If genetically transmitted, it may be generalized or focal, with symptoms varying in different members of the same family. It may be refractory to treatment, or it may respond to any one of a number of individual drugs that have very different mechanisms of action. For idiopathic dystonias, no clear method of genetic transmission has been established and no consistent pathology identified.

Pathologic changes in the brain in cervical dystonia pre- and post-mortem - a commentary with a special focus on the cerebellum

In a recent issue of Experimental Neurology, Prudente et al. (2012) investigated the neuropathology of cervical dystonia in six patients. Their most important finding was a patchy loss of cerebellar Purkinje cells in the cerebellum. In this article we discuss their findings in the context of a review including primary and secondary cervical dystonia. An update is given of the current knowledge on structural and functional brain abnormalities in idiopathic cervical dystonia with a special focus on the cerebellum.

Neuropathology of cervical dystonia

The aim of this study was to search for neuropathological changes in postmortem brain tissue of individuals with cervical dystonia (CD). Multiple regions of formalin-preserved brains were collected from patients with CD and controls and examined with an extensive battery of histopathological stains in a two-stage study design. In stage one, 4 CD brains underwent a broad screening neuropathological examination. In stage two, these 4 CD brains were combined with 2 additional CD brains, and the subjective findings were quantified and compared to 16 age-matched controls. The initial subjective neuropathological assessment revealed only two regions with relatively consistent changes. The substantia nigra had frequent ubiquitin-positive intranuclear inclusions known as Marinesco bodies. Additionally, the cerebellum showed patchy loss of Purkinje cells, areas of focal gliosis and torpedo bodies. Other brain regions showed minor or inconsistent changes. In the second stage of the analysis, quantitative studies failed to reveal significant differences in the numbers of Marinesco bodies in CD versus controls, but confirmed a significantly lower Purkinje cell density in CD. Molecular investigations revealed 4 of the CD cases and 2 controls to harbor sequence variants in non-coding regions of THAP1, and these cases had lower Purkinje cell densities regardless of whether they had CD. The findings suggest that subtle neuropathological changes such as lower Purkinje cell density may be found in primary CD when relevant brain regions are investigated with appropriate methods.

Human T-cell responses to botulinum neurotoxin. Responses in vitro of lymphocytes from patients with cervical dystonia and/or other movement disorders treated with BoNT/A or BoNT/B

We have previously reported that botulinum neurotoxin type A (BoNT/A)-specific T-cell responses occur in a majority of patients treated with botulinum neurotoxins (BoNT). In this study, we first determined if T-cell responses against BoNT/A and tetanus toxin (TeNT) differ between cervical dystonia (CD) patients and other movement disorder cases. Secondly, we have examined in CD cases the treatment parameters that may have an effect on the T-cell responses against BoNT/A. We found that T-cell responses to BoNT/A were significantly higher in patients with CD than in those with other movement disorders. An increase in TeNT T-cell response in CD was observed when compared to un-treated controls. CD patients who were injected with BoNT/B mounted higher responses to BoNT/A than patients treated with BoNT/A only. Frequent injections (more than 2.1/year) were associated with a significantly higher T-cell response to BoNT/A in CD. T cell responses to BoNT/A did not differ between CD patients who had clinically responsive and non-responsive status at the time of enrollment.

Homocysteine and serum markers of immune activation in primary dystonia

The cause of primary dystonia remains unknown. Several reports point to immune system disturbances in primary dystonia and a recent study demonstrated hyperhomocysteinemia in cervical dystonia. Homocysteine (HCY) is an amino acid and elevated HCY concentrations were shown to be associated with immune system activation and increased neopterin serum concentrations. We examined HCY serum concentrations together with serum markers of immune activation in patients with different types of primary dystonia. Eighty-three patients with different types of primary dystonia were included and investigated at least 3 months following botulinum toxin treatment. Thirty-six healthy volunteers with similar age and sex distribution served as controls. Total serum HCY, kynurenine, and tryptophan concentrations were determined by high-performance liquid chromatography; neopterin, folate, and vitamin B12 concentrations were measured by immunoassays. Routine blood analysis, including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood count (WBC), was performed. Patients with primary dystonia had significantly higher HCY concentrations compared to controls. Among the dystonia subtypes, no significant difference of HCY serum concentrations was observed. CRP and ESR were within the normal range in >90% of the patients and all had normal WBC. Neopterin, kynurenine, and tryptophan serum concentrations were similar in patients and controls and not correlated with HCY serum concentrations. The results provide evidence against enhanced cellular immune activation in patients with primary dystonia. However, hyperhomocysteinemia was present in all dystonia subtypes and unrelated to immune activation in this study. HCY is a neuronal excitotoxic amino acid and hyperhomocysteinemia is considered an independent vascular risk factor. Further studies are required to define the background of hyperhomocysteinemia in primary dystonia.