Study On The Role Of T Lymphocyte-related Immune Disorders In Parkinson's Disease

Parkinson's disease(PD)is one of the most common neurodegenerative disorders,with major clinical manifestations,including resting tremor,tetanus,bradykinesia,and posture.At present,there still lack accurate diagnosis and effective treatment for PD.Most PD patients have idiopathic causes.Inflammation is a common manifestation of degenerative diseases including PD and Alzheimer's disease.Adaptive immune responses mediated by T lymphocytes play an important role in neuroinflammation and pathogenesis of neurological diseases.Understanding the adaptive immune system has an important diagnostic and therapeutic value in the pathogenesis of neurodegenerative diseases.Inflammation exists not only in the brain,but also the peripheral immune system,which is believed to be involved in the occurrence and development of the neurodegenerative process of PD.Therefore,it is important to explore the roles of T cells,a key component of the immune system,in the pathogenesis of PD.In this project,we have conducted the following studies.In Part I,we characterized the levels of peripheral blood lymphocytes in PD patients and healthy volunteers from the first cohort.In the preceding second cohort,we focused on the abundance of Th1 effector T cells and regulatory T cells(Treg)in PD patients and healthy volunteers.In the animal experiments,we manipulated the abundance of Th1 and Treg in mice with PD to determine the roles of these two cell types.In Part II,we explored the dentirmental roles of T cells and the mechanisms of T cell in filtration in the central nervous system.We are hoping that findings in this project will facilitate treatment for patients with PD.Part ?: Imbalance between CD4+ effector T cells and Treg is critical in the pathogenesis of Parkinson's disease Objective: To determine whether imbalance between Th1 and Treg exits in the peripheral circulation of PD patients.To explore the mechanisms of this imbalance in mediating PD in experimental mice.Methods: In exploring Cohort 1,we detected the levels of circulating T lymphocytes in 32 PD patients and 16 age-and sex-matched healthy volunteers.The severity of PD was classified according to the Hoehn-Yahr standard into severe and mild diseases.In Cohort 2,we focused on the imbalance between Th1 effector cells(CD3+CD4+T-bet+)and Treg(CD3+CD4+CD25+Fox P3+)in PD patients and matched healthy volunteers.In mice with experimental PD,the abundance of Th1 and Treg was also documented.Anti-mouse CD25 antibodies were utilized to deplete Treg.CD25+ cells were transferred to PD mice to increase the abundance of Treg.Anti-TNF-? antibodies were applied to mice to abolish effects of Th1 cells.Open-field assessments were used to measure the severity of experimental PD in mice.Results: In Cohort 1,the abundance of immune cells in the circulation of PD patients and healthy volunteers were measured.PD patients had decreased numbers of CD19+lymphocytes(p=0.021)and CD3+HLA-DR+ T lymphocytes(p=0.045)compared to healthy volunteers.More importantly,the percentage of CD4+CD25+ T cells was lower in the blood of PD patients(p=0.013),indicating Treg might have an important role in PD.In Cohort 2,we conducted more specific experiments targeting Th1 and Treg cells.Compared to healthy volunteers,PD patients had fewer Treg and more Th1 cells in the blood.Similarly,there were decreased numbers of Treg and increased numbers of Th1 in the blood of mice with PD.When treated with anti-CD25 antibodies,PD mice harbored even lower numbers of Treg and more severe disease phenotypes measured by open-field tests.Moreover,anti-TNF-? antibodies applications decreased the severity of experimental PD in mice.PD mice receiving CD25+ cells showed attenuated disease.Mechanistically,application of anti-TNF-?antibodies and CD25+ cell transfer increased the abundance of Treg and decreased that of Th1 in the brain of mice with PD.Conclusion: Increased numbers of Th1 and/or decreased numbers of Treg play a critical role in the pathogenesis of PD.Part ?: Interaction between ICAM1 expressed by endothelial cells and LFA1 expressed by T cells in the pathogenesis of Parkinson's disease Objective: In Part 1 of the project,we found that excessive Th1 infiltration in the central nervous system is critical for the pathogenesis of experimental PD.However,how T cells are recruited in the brain and by what mechanisms they are involved in the pathogenesis of PD remains unclear.To explore the mechanisms underlying the process of T cell infiltration in the brain,we examined the roles of intercellular adhesion molecules in experimental PD.Methods: MPTP-induced experimental PD in mice was conducted.Numbers of CD4+ and CD8+ T cells in the brain were examined using immunofluorescence.Depletion of CD4+ T or CD8+ T cells were achieved by using neutralizing antibodies.Tyrosine hydroxylase(TH)-expressing cells were stained and counted by using immunofluorescence.Open-field assessments were used to measure the severity of experimental PD in mice.Adhesion molecules were detected by flow cytometry.Antibodies againsed ICAM1 and LFA1 were administered to mice to block the interaction between ICAM1 and LFA1.Results: There were significantly more CD4+T cells and CD8+T cells in the brain tissues of MPTP-induced PD mice,which mainly located in the SNpc and striatum regions.Blocking CD4+ or CD8+ T cells reduced the severity of PD in mice,and the number of neuroprotective TH+ cells increased.Endothelial adhesion molecule 1(ICAM1,or CD54)was up-regulated in the brain tissues of PD mice,and its receptor lymphocyte function related antigen(LFA)1 was also overexpressed in T cells.In addition,inhibition of ICAM1 or LFA1 increased the number of TH+ cells and improve disease severity.Therefore,the interaction between ICAM1 and LFA1 plays an important role in recruitment of T cells in the central nervous system to mediate experimental PD.Conclusion:Experimental PD in mice is mediated by CD4+ and/or CD8+ T cells.Endothelial ICAM1 and LFA1 expressed by T cells interact with each other to recruit T cells in the central nervous system.