V region T cell receptor repertoire in Parkinson's disease

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

[Immunological aspects of Parkinson's disease]

The review summarizes information on immunological disorders in Parkinson's disease (PD). The data on neuroinflammation associated with degeneration of the medial substantia nigra cells are presented. It is pointed out that innate and adaptive immunity cells are involved in the process of neuroinflammation. The authors analyze the cytokine level in the brain, cerebrospinal fluid and peripheral blood as well as the relationship between neuroinflammation and neuron dysfunction and provide information on immunological disorders in people with PD and animal models of PD. Specific features of PD models and data on blood-brain barrier damage and evidence of autoimmune inflammation in PD are presented. Identification of PD preclinical markers, including cytokines, HLA-DR and HLA-DQ antigens, autoantibodies, etc, is discussed. Pre-symptomatic diagnosis of PD, prevention and treatment at the pre-symptomatic stage could lead to interruption or slowdown the neurons death.

Inflammation, Infectious Triggers, and Parkinson's Disease

Parkinson's disease is a neurodegenerative disorder characterized by progressive loss of dopaminergic neurons of the substantia nigra pars compacta with a reduction of dopamine concentration in the striatum. The complex interaction between genetic and environmental factors seems to play a role in determining susceptibility to PD and may explain the heterogeneity observed in clinical presentations. The exact etiology is not yet clear, but different possible causes have been identified. Inflammation has been increasingly studied as part of the pathophysiology of neurodegenerative diseases, corroborating the hypothesis that the immune system may be the nexus between environmental and genetic factors, and the abnormal immune function can lead to disease. In this review we report the different aspects of inflammation and immune system in Parkinson's disease, with particular interest in the possible role played by immune dysfunctions in PD, with focus on autoimmunity and processes involving infectious agents as a trigger and alpha-synuclein protein (α-syn).

The role of innate and adaptive immunity in Parkinson's disease

In recent years, inflammation has become implicated as a major pathogenic factor in the onset and progression of Parkinson's disease. Understanding the precise role for inflammation in PD will likely lead to understanding of how sporadic disease arises. In vivo evidence for inflammation in PD includes microglial activation, increased expression of inflammatory genes in the periphery and in the central nervous system (CNS), infiltration of peripheral immune cells into the CNS, and altered composition and phenotype of peripheral immune cells. These findings are recapitulated in various animal models of PD and are reviewed herein. Furthermore, we examine the potential relevance of PD-linked genetic mutations to altered immune function and the extent to which environmental exposures that recapitulate these phenotypes, which may lead to sporadic PD through similar mechanisms. Given the implications of immune system involvement on disease progression, we conclude by reviewing the evidence supporting the potential efficacy of immunomodulatory therapies in PD prevention or treatment. There is a clear need for additional research to clarify the role of immunity and inflammation in this chronic, neurodegenerative disease.

Amantadine in Parkinson's disease: lymphocyte subsets and IL-2 secreting T cell precursor frequencies

The antiviral drug amantadine, that is effective in idiopathic Parkinson's disease (PD), may affect the composition and function of peripheral blood lymphocytes. In an explorative study, we therefore compared lymphocyte subpopulations and IL-2 secreting T cell precursors frequencies (HTLp-frequencies) in 15 PD patients without amantadine and six patients on long-term treatment. Five patients were investigated before and three months after the start of treatment. Group comparisons for long-term amantadine treatment showed no differences in subpopulations of B-, T-, and NK cells, and HTLp-frequencies. However, three months after initiation of treatment we noted in all five patients an increase of CD3+CD4+ and decrease of CD3+CD8+ cells, associated with an increase of the CD3+CD4+/CD3+CD8+ ratio. These changes had no effect on the HTLp-frequencies. Thus, at least for a short period of time, amantadine improves the T cell mediated immune system in PD patients.

Does Parkinson's disease have an immunological basis? The evidence and its therapeutic implications

Parkinson's disease (PD) is an age-related neurodegenerative movement disorder of unknown aetiology. Immune abnormalities have been described in PD including the occurrence of autoantibodies against neuronal structures and high numbers of microglia cells expressing the histocompatibility glycoprotein human leucocyte antigen-DR in the substantia nigra. An infectious cause for PD has been discussed for years. Disturbed cellular and humoral immune functions in peripheral blood of patients with PD have been also reported. An elevated gammadelta(+) T cell population and increased immunoglobulin G immunity in CSF to heat shock proteins have been found in PD. Cytokines and apoptosis-related proteins were elevated in the striatum in patients with PD. Activated glial cells may participate in neuronal cell death in PD by providing toxic substances. We may conclude that the immune system is involved in the pathogenesis of PD. However, we are not able to determine whether the disturbances described above constitute a primary or secondary phenomenon. Immunomodulatory agents may have important applications in the development of new therapies for PD.