[Animal models in neurology: prospects and limitations]. / Tiermodelle in der Neurologie: Möglichkeiten und Grenzen.

Animal models play an important role for exploration of the aetiology, pathogenesis and therapy of various neurological diseases. Their benefit and limitations are being discussed mainly focussed at experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS). To answer specific questions concerning the genetics, pathogenesis, diagnostics and treatment of inflammatory, degenerative, ischemic, traumatic und neoplastic diseases of the nervous system different animal models are needed. So far, these are only partially available. Rarely there are alternative methods such as cell, tissue and organ cultures and computer simulations. New phase-specific biomarkers are needed in order to improve the potency of experimental results to be translated into clinical practice.

Monoclonal antibodies in the therapy of multiple sclerosis: an overview.

With the generation of monoclonal antibodies (mAbs), a new therapeutical concept has gained importance. MAbs aim against selective antigens and so have changed our treatment strategies from non-specific to specific. Four therapeuticals have gained importance in the therapy of multiple sclerosis (MS): One has already been approved for therapy (natalizumab), whereas the other three are either in clinical trials or are about to enter phase III studies. Currently, two phase III studies that evaluate the efficacy of alemtuzumab have begun with recruitment (MS CARE I and II). Another mAb (daclizumab) under study is directed to the interleukin-2alpha chain (CD25). Results of clinical trials are promising by reporting reduction of relapses and progression in relapsing remitting and secondary progressive MS accompanied by reduction of new lesions in magnetic resonance imaging. A multicenter randomized controlled trial of daclizumab in MS is going to be initiated. Trials with a humanised antibody directed against the cell surface molecule CD20 are under development. Although the future will emphasise this trend to mAbs, the risks should not be ignored as has been shown in recent news. Still, mAbs have the possibility to revolutionise therapeutical concepts in the treatment of immune-mediated diseases, and will therefore be a useful addition to current therapeutic concepts.

Detection of apoptotic cells in cerebrospinal fluid of patients suffering from neurological disease.

Apoptotic elimination of pathogenic immune cells is considered one of several regulatory mechanisms in inflammatory diseases. To explore the potential relationship between detection of apoptotic cells in the cerebrospinal fluid (CSF) and different types of neurological diseases, we examined cellular apoptosis at the stage of DNA fragmentation, defined by morphological criteria and a molecular biology technique (in situ tailing). During a first phase, 3446 CSF samples derived from admitted patients suffering of inflammatory (IND) and non-inflammatory neurological diseases (NIND) were analysed in the course of routine clinical diagnostics. First, all specimens were inspected for cells displaying atypical morphology following established morphological criteria of intact lymphocytes or apoptosis. In a second phase, 76 additional CSF samples collected from individuals according to investigated clinical groups were analysed in parallel by means of in situ tailing, which indicates the advanced degree of apoptotic demise through labelling of controlled DNA fragmentation. No apoptotic processes were detected by either analytical method in CSF of clinically distinct diseases, amongst others multiple sclerosis (MS). This indicates that the detection of apoptotic cells in CSF during clinical routine diagnostics does not have sufficient explanatory power for the investigated conditions. Furthermore, based on immunohistochemistry, the proportion of CSF lymphocytes expressing the pro-apoptotic receptor Fas (CD95) tended to be higher in NIND patients compared to patients with other IND and MS, but the difference was not statistically significant. In contrast, expression of the anti-apoptotic protein Bcl-2 did not differ between investigated patient groups.

H2O2 and nitric oxide-mediated oxidative stress induce apoptosis in rat skeletal muscle myoblasts.

In many degenerative and metabolic muscle diseases cells die without a marked inflammatory response. A potential mechanism how this could be accomplished is apoptotic cell death. Since there are no data available about apoptosis in cells of myogenic origin, we examined rat skeletal myoblasts for their potential to undergo apoptosis when exposed to reactive oxygen intermediates and nitric oxide. We observed morphologic changes typical for apoptotic cell death, and DNA fragmentation was confirmed by gel electrophoresis and molecular labeling assays. With these methods we could show that both reactive oxygen intermediates and nitric oxide can induce apoptosis in myoblasts in a dose-dependent manner. These results are discussed with regard to possible implications on the pathophysiology of various muscle diseases.

Cytokine production and the pathogenesis of experimental autoimmune neuritis and Guillain-Barré syndrome.

Acute inflammatory demyelinating polyradiculoneuropathy (Guillain-Barré syndrome, GBS) and its animal model experimental autoimmune neuritis (EAN) are prototypes of T cell-mediated autoimmune diseases affecting the peripheral nervous system (PNS). Perivascular accumulation of macrophages and T lymphocytes in the PNS, and high levels systemically of PNS myelin antigen-reactive T cells are characteristic features of both diseases, thereby suggesting a pathogenic role for immunoregulatory cytokines. Here we summarise recent studies that have clearly documented that Th1/Th2/Th3 cytokines are differently upregulated during various clinical phases of EAN and GBS. The observations indicate that the role of cytokines in immune regulation and autoimmune disease is more complex than a simple Th1-Th2 dichotomy would suggest. New treatments may be searched for that counteract this complex cytokine imbalance. Treatments with antibodies that selectively target certain pro-inflammatory cytokines, as well as with immunomodulatory preparations that promote cytokines that beneficially influence the disease course should be in focus of future therapeutic trials.

Experimental allergic neuritis: cytolysin mRNA expression is upregulated in lymph node cells during convalescence.

Experimental allergic neuritis (EAN) is a T cell mediated animal model of Guillain-Barré syndrome, characterized by inflammation and demyelination of the peripheral nervous system (PNS). To study the involvement of immunoregulatory cytokines, we induced EAN in Lewis rats by immunizing with bovine PNS myelin (BPM) and Freund's complete adjuvant. mRNA expression of the cytokines IL-1beta, IL-6, IL-10, IL-12, TNF-alpha and TNF-beta, and the cytolytic effector molecule cytolysin was examined in lymph node mononuclear cells (MNC) over the course of EAN by in situ hybridization after culture without antigen and in the presence of BPM, the myelin P2 protein, the control antigen acetylcholine receptor, or the mitogen PHA. Three patterns of cytokine mRNA expressing MNC in relation to clinical EAN could be distinguished: (i) IL-1beta mRNA expressing cells peaked already on day 3 post immunization (p.i.), and BPM- and P2-reactive TNF-alpha, and BPM-reactive IL-6 mRNA expressing cells were also detected already on day 7 p.i., i.e., before onset of clinical EAN; (ii) BPM- and P2-reactive TNF-alpha peaked together with P2-reactive TNF-beta, IL-6 and IL-12 mRNA expressing cells at height of clinical EAN, consistent with a disease-promoting role for these four cytokines; (iii) high levels of BPM- and P2-reactive IL-10 and cytolysin mRNA expressing cells were observed only during recovery (day 28 p.i.), consistent with a disease down-regulating role of IL-10 and cytolysin. The results suggest a major proinflammatory role for IL-1beta, TNF-alpha, TNF-beta, IL-6 and IL-12 and a disease down-regulating function of IL-10 as well as cytolysin in EAN.

V delta 1 gene usage, interleukin-2 receptors and adhesion molecules on gamma delta+ T cells in inflammatory diseases of the nervous system.

This study investigates the expression of T cell receptor V delta 1 chain, interleukin-2 receptor alpha-chain (CD25) and adhesion molecules ICAM-1 (CD54), LFA-1 (CD11a/18) and CD44 on gamma delta+ T cells by three-color flow cytometry on cerebrospinal fluid (CSF) and blood cells in patients with multiple sclerosis (MS), other inflammatory neurological diseases (OIND) and other neurological diseases (OND). Of gamma delta + T cells in CSF and blood, 20-40% belonged to the 'epithelial' V delta 1 subtype. MS patients had the lowest levels in both CSF and blood, but the differences between the patient groups were not significant. The activation markers CD25 and CD54 were expressed by only a small proportion of gamma delta+ T cells and in a minority of patients. Although the occurrence of CD25+ and CD54+ gamma delta+ T cells was somewhat higher in CSF than in blood and in inflammatory diseases than in controls, the small numbers of CD25+ and CD54+ gamma delta+ T cells preclude establishing differences amongst compartments and patient groups. The adhesion molecules CD11a/18 and CD44 were constitutively expressed on all T cells. Therefore, we compared the relative antigen density per cell as measured by the relative fluorescence index (RFI) between CSF and blood, between the patient groups and between gamma delta+ and total T cells. The only difference encountered was a slightly higher expression of adhesion molecules on gamma delta+ compared to total T cells, with preference to MS patients. In conclusion, the V delta 1+ subtype of gamma delta+ T cells does not dominate in the CSF compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

CD5+ B cells and CD4-8-T cells in neuroimmunological diseases.

Using 2- and 3-colour FACS analysis we found increased levels of fetal-type CD5+ B cells and CD4-8- T cells in cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) and aseptic meningitis (AM) compared to control probands with muscular tension headache (TH). Similar differences were found for CD5+ B cells in peripheral blood, but at lower levels. CD4-8- T cells in blood exceeded those in CSF in all patient groups, with the exception of relapsing remitting MS, revealing the highest values in AM. There was a positive correlation between CD4-8- T cells and T cell receptor (TCR) gamma delta bearing T cells in blood and CSF. The double-negative T cells exceeded the TCR gamma delta T cells by about 1%. A positive correlation between CD5+ B cells and CD4-8- T cell level in CSF was found in MS and AM, but not in TH, nor in blood of any patient group. HLA-DR expression was lower in CD5+ B cells than in CD5- B cells. We conclude that fetal-type lymphocytes are enriched in CSF compartment of patients with inflammatory diseases of the central nervous system, irrespective of autoimmune mechanisms involved, but the function of CD5+ B cells is mainly to produce the autoantibodies.

Apoptosis induction by macrophage-derived reactive oxygen species in myelin-specific T cells requires cell-cell contact.

Apoptosis of autoreactive T cells has been recognized as an important mechanism of immune homeostasis in autoimmune PNS diseases. To examine whether T cells are induced to undergo apoptosis by macrophages (Mphi) via reactive oxygen species (ROS) neuritogenic P2-specific T line cells were exposed to peritoneal Mphi of Lewis rats in vitro. ROS production was stimulated by phorbol myristate acetate (PMA) and inhibited by catalase. Flow cytometric analysis of apoptosis as measured by TUNEL technique revealed that 5-15% of all P2-cells were apoptotic, if cultured alone. This percentage increased slightly, but did not exceed 20% when P2-cells were cocultivated with PMA-stimulated Mphi in a two-chamber culture plate separated by a cell-impermeable membrane. Direct cocultivation caused apoptotic cell death of more than 40% of P2-cells, which was completely abrogated by catalase. These results suggest a requirement for close cell-cell contact for apoptosis induction of T cells via Mphi-derived ROS. Thus Mphi may contribute to termination of inflammation in vivo through the release of highly reactive oxygen species that mediate apoptotic cell death of autoaggressive T lymphocytes.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) blockade enhances incidence and severity of experimental autoimmune neuritis in resistant mice.

Experimental autoimmune neuritis (EAN), an autoimmune inflammatory demyelinating disease of the peripheral nervous system, represents an animal model of the human Guillain-Barré syndrome. EAN can be induced by active immunization in several animals, including Lewis rats. In contrast, most strains of mice including the widely used C57BL/6 (B6) strain are reputedly resistant to the induction of EAN. In the present study, we demonstrate that in B6 mice, anti-CTLA-4 monoclonal antibody administration in conjunction with immunization with the P0 protein derived peptide 180-199 can induce clinical and pathological definite EAN. Upregulating effects of CTLA-4 blockade on initial and ongoing EAN are demonstrated. CTLA-4 blockade augmented cellular infiltration and enhanced demyelination in the target organ sciatic nerves as well as increased T cell proliferation in lymph node cells. Moreover, serum levels of IFN-gamma and IL-4 were increased. Thus, manipulation of CTLA-4/B7 costimulatory pathway by CTLA-4 blockade can promote autoreactivity and break the relative tolerance to peripheral autoantigen P0 in resistant B6 mice.

P0 glycoprotein peptides 56-71 and 180-199 dose-dependently induce acute and chronic experimental autoimmune neuritis in Lewis rats associated with epitope spreading.

Two synthetic peripheral nerve myelin P0 protein peptides, an immunodominant (amino acids 180-199) and a cryptic (amino acids 56-71) one, induced an acute or chronic course of experimental autoimmune neuritis (EAN) in Lewis rats, when given at low dose (50-100 microg/rat) or high dose (250 microg/rat), respectively. Corresponding to the different clinical course, pathological changes and immune responses were found: (1) Onset of clinical signs of P0 peptide 56-71 (P0 56-71) induced EAN was 1-3 days later than in P0 peptide 180-199 (P0 180-199) induced EAN at all immunizing doses, whereas the peak of the disease occurred at a similar time point post immunization (p.i.), i.e. at days 14-16 p.i. in P0 56-71 induced EAN and at day 16 p.i. in P0 180-199 induced EAN. (2) Intramolecular epitope spreading as assessed by delayed type hypersensitivity response occurred in P0 56-71 induced EAN at both low and high antigen doses and in P0 180-199 induced EAN at high antigen dose (250 microg/rat) only. (3) P0 180-199 stimulated higher levels of interferon-gamma production in P0 180-199 induced EAN than in P0 56-71 induced EAN and vice versa. (4) Histopathologic evaluation revealed a similar grade of mononuclear cell infiltration in the sciatic nerves of both types of EAN, but more severe demyelination was found in P0 180-199 induced EAN compared to P0 56-71 induced EAN. The results support the hypothesis that high dose autoantigen immunization induces extensive determinant spreading and chronic course of autoimmune diseases.

CD28-B7 costimulation: a critical role for initiation and development of experimental autoimmune neuritis in C57BL/6 mice.

CD28 provides a critical costimulatory signal for antigen-specific T cell activation. Because CD28 is an important factor in the development of autoimmune diseases, we investigated its role in T cell-mediated experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome in humans. CD28-deficient mutant (CD28-/-) C57BL/6 mice and corresponding wild-type mice were immunized with P0 peptide 180-199, a purified component of peripheral nerve myelin, and Freund's complete adjuvant. As a result, all wild-type mice developed severe EAN, in contrast, none of the CD28-/- mice manifested clinical signs of disease. Additionally, CD28-/- mice had fewer IL-12 producing cells in sciatic nerve sections and fewer IFN-gamma secreting splenic cells than wild-type mice on day 24 post immunization, i.e., at the peak of clinical EAN. At that time point, CD28-/- mice had milder infiltration of such inflammatory cells as macrophages, CD4+ T cells and monocytes into sciatic nerve tissues and less demyelination than wild-type mice. Moreover, the CD28-deficiency led to reduced production of specific anti-P0 peptide 180-199 antibodies compared with wild-type mice. Evidently, CD28 is required for interaction with B7 to regulate the activation of T and B cells that initiates development of EAN.

Antigen-specific immunosuppression: nasal tolerance to P0 protein peptides for the prevention and treatment of experimental autoimmune neuritis in Lewis rats.

Experimental autoimmune neuritis (EAN) is an autoimmune inflammatory demyelinating disease of the peripheral nervous system (PNS), and represents an animal model of the human Guillain-Barré syndrome (GBS). In this study, we report that nasal administration of the neuritogenic peptide 180-199 and of the cryptic peptide 56-71 of the rat neuritogenic P0 protein of peripheral nerve myelin prevents EAN and attenuates ongoing EAN. Both peptides effectively decreased the severity and shortened clinical EAN. Both a prophylactic and a therapeutic approach proved to be beneficial. These effects were associated with T and B cells hyporesponsiveness to the peptide antigens, reflected by downregulated Th1 cell responses (interferon-gamma secretion) and macrophage function, whereas Th2 cell responses (IL-4 secretion) and transforming growth factor-beta mRNA expression were upregulated.

Induction of experimental autoimmune neuritis in CD4-8-C57BL/6J mice.

The C57BL/6J mice strain is known to be reputedly resistant to induction of experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome in humans. Here we describe the induction of EAN in mice of the C57BL/6J background by transfer into naive syngeneic recipients bovine peripheral nerve myelin (BPM)-primed donor lymph node cells that had been stimulated in vitro with the bovine peripheral nervous system (PNS) myelin P2 protein peptide 57-81 followed by challenge with BPM, Freund's complete adjuvant and pertussis toxin. EAN was more severe, both clinically and histologically, and accompanied by extensive infiltration of inflammatory cells and demyelination in peripheral nerves when examined on day 30 after transfer of primed T cells from CD4- 8- mice into identical naive hosts than after transfer of cells from primed wild type, CD4-/- or CD8-/- mice to corresponding recipient animals. EAN in CD4-8- mice was also associated with elevated numbers of P2 peptide-reactive interferon-y (TFN-gamma) secreting cells and alphabeta T cells were present in lymph nodes and spleens. The data suggest that PNS myelin activated T cells from an EAN-resistant mice strain are capable of homing to the PNS. The expanded CD4-8- alphabeta T cells may have helper and effector functions, related to initiation of EAN in the CD4-8- mice. Lack of CD4+ and CD8+ expressing cells does not prevent the initiation of an autoimmune disease.

Dynamics of production of MIP-1alpha, MCP-1 and MIP-2 and potential role of neutralization of these chemokines in the regulation of immune responses during experimental autoimmune neuritis in Lewis rats.

Experimental autoimmune neuritis (EAN) is an inflammatory autoimmune demyelinating disease of the peripheral nervous system (PNS) and represents an animal model of Guillain-Barré syndrome (GBS), which is a major inflammatory demyelinating disease of the PNS in humans. In the present study, the dynamics of the expression of the chemokines macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-2 and monocyte chemotactic protein-1 (MCP-1) were determined in the sciatic nerves of EAN rats. Additionally, the effect of neutralizing antibodies against MIP-1alpha, MIP-2 and MCP-1 on the clinical course of EAN and the chemokine expression was investigated. The maximum of MIP-1alpha positive cells in the sciatic nerves was seen on day 14 post immunization (p.i.) correlating with the development of severe clinical signs. Administration of an anti-MIP-1alpha antibody suppressed the clinical signs of EAN and inhibited inflammation and demyelination in the sciatic nerve. Peak numbers of MCP-1 positive cells in the sciatic nerves were detected on day 7 p.i. Administration of an anti-MCP-1 antibody caused a delay of onset of EAN. However, 4 of the 6 EAN rats receiving the anti-MCP-antibody showed the same degree of inflammatory cell infiltration and demyelination in the sciatic nerves as sham-treated EAN rats, whereas only 2 EAN rats had less inflammation and demyelination. The numbers of MIP-2 positive cells reached a maximum on day 21 p.i. Anti-MIP-2 antibody failed to suppress the clinical signs of EAN and the inflammation and demyelination in the sciatic nerves. Only administration of the anti-MIP-1alpha antibody resulted in a significant reduction in the number of chemokine (MIP-1alpha)-positive cells and ED1-positive macrophages in the sciatic nerves. The present results demonstrate that MIP-1alpha and MCP-1 may play a role in the immunopathogenesis of EAN, and that MIP-1alpha induced trafficking of inflammatory cells can be inhibited by immunoneutralization. Further elucidation of the regulation and coordination of MIP-1alpha and MCP-1 production may lead to new therapeutic approaches to GBS in humans.

Influence of K+ channel openers on interferon-gamma dependent immune response in experimental allergic neuritis (EAN).

We examined the influence of the K+ channel opening drugs BRL 38227, pinacidil and diazoxide on cellular immune response and clinical course of experimental allergic neuritis (EAN) actively induced in Lewis rats by bovine peripheral myelin (BPM). T cell functions of EAN lymph node cells were assessed by measurement of proliferation and by counting of interferon-gamma secreting cells (IFN-gamma sc) in response to the specific antigen BPM and the T cell mitogen phytohemagglutinin (PHA). BRL 38227 and diazoxide at concentrations of 10(-5)M-10(-6)M and pinacidil at concentrations of 10(-5)M-10(-7)M enhanced the proliferative response to both BPM and PHA. The number of IFN-gamma sc was suppressed by the K+ channel openers in the same concentration range. There was a tendency of stronger suppression of cultures with high numbers of BPM-reactive IFN-gamma sc than of cultures with low numbers of BPM-reactive IFN-gamma sc. The applied K+ channel openers are primarily acting on ATP-sensitive K+ channels, which have not been found in T cells so far. The drugs may, therefore, exert non-selective effects on conventional voltage- and/or Ca(++)-dependent channels of T cells. A first trial with in vivo administration of 2.5 mg/kg x day of the drugs resulted in more severe neurological deficits in the early phase of EAN with BRL 38227, whereas pinacidil and diazoxide had no significant effects.

Oxides and apoptosis in inflammatory myopathies.

Reactive oxygen intermediates (ROI) and nitric oxide (NO(.)) are produced in abundance in the inflammatory muscle diseases of autoimmune origin polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). However, their role in the pathogenesis of these diseases is so far not clear. In contrast to demyelinating neuropathies, there is no convincing evidence for oxide-induced apoptosis either in myocytes or in lymphocytes and phagocytes in inflammatory myopathies. On the contrary, NO(.) released at low concentrations at target sites may even have cell-protective effects. A major mechanism of protection from apoptosis in both myocytes and inflammatory cells seems to be the upregulation of anti-apoptotic proteins like Bcl-2. Caution is warranted to apply antioxidative and anti-apoptotic agents to patients with inflammatory myopathies as long as the pathogenic role of oxides and apoptosis in the individual case is not resolved.

Phagocytic activity of CSF monocytes in neurological diseases.

A standard latex phagocytosis test was used to determine the phagocytic activity of CSF monocytes under various pathological conditions. The mean values for groups of neurological diseases did not differ significantly, with the exception of tumour patients. Differences in the phagocytosis of CSF monocytes were seen if subdivisions within the groups of patients with multiple sclerosis (MS) and vertebral irritation syndrome (VIS) were evaluated separately. The active stage of MS and the intervertebral disc prolapse were accompanied by higher values. It is concluded that although the findings are of no use for diagnostic purposes they may be helpful in assessing prognosis and therapy.

The B cell repertoire in experimental allergic neuritis involves multiple myelin proteins and GM1.

Experimental allergic neuritis (EAN) is a T cell mediated disease associated with inflammation and demyelination of peripheral nerves. EAN is an experimental model of Guillain-Barré syndrome. The peripheral nerve myelin components P2 and P0 represent major neuritogens, but the diversity and quantity of B cell responses in EAN are unknown. Lewis rats were immunized with bovine peripheral nerve myelin (BPM), and levels of B cells secreting IgM and IgG antibodies to BPM, P2 and P0, the glycolipid GM1 and five peptides of myelin-associated glycoprotein (MAG) were determined. Already on day 7 post-immunization (p.i.), i.e. before the onset of clinical EAN, lymph nodes contained elevated levels of cells secreting IgM antibodies of all specificities examined. Maximum numbers of IgG antibodies secreting cells were generally reached at the height of clinical disease. The numbers of cells secreting IgG antibodies to BPM, P2, P0, GM1 and MAG peptides were also elevated before disease onset, but they were mostly higher than those of IgM antibodies and they reached their maximum only after recovery. The results imply that EAN is associated with strong B cell responses to all myelin antigens under study without restriction to any immunodominant myelin component or MAG peptides.

gamma delta+ T cells are increased in patients with Parkinson's disease.

The etiology of Parkinson's disease is mainly unknown. Immune abnormalities have been reported, including the occurrence of autoantibodies against neuronal structures and abnormal T cell functions. gamma delta+ T cells represent a recently recognized T cell subpopulation which is considered to play a role in immune responses in infections and autoimmunity. We examined by three-colour flow cytometry the proportions of gamma delta+ T cells in blood and cerebrospinal fluid (CSF) from patients with Parkinson's disease. Increased proportions of gamma delta+ T cells were found in CSF in Parkinson's disease compared to other neurological diseases (OND) and tension headache. In peripheral blood, patients with Parkinson's disease had higher numbers of gamma delta+ T cells compared to OND patients. No differences between gamma delta+ T cells in CSF compared to blood were demonstrable in the individual patient groups. CD25 was not expressed on gamma delta+ T cells in blood of the majority of cases, but 50% of patients with Parkinson's disease and 30% with OND and tension headache had CD25+ gamma delta+ T cells in CSF arguing for a preferential activation of gamma delta+ T cells in the CSF compartment. Whether the elevated gamma delta+ T cell population in Parkinson's disease reflects previously unrecognized inflammation or may occur also in non-inflammatory disorders remains to be elucidated.