Importance Of The Abnormalities Of Regulatory T Cells In The Pathogenesis Of Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is an antigens drove and T cell mediatedautoimmune disease. The abnormalities of the T cell function is thought toplay an important role in the RA pathogenesis. It has been found by recentstudies that regulatory T cells (Treg) is a very important component whichmaintains immunological tolerance. These T cells have the function ofsuppressing immune response, which can suppress the activation andproliferation of CD4+ and CD8+ cells. To explore the importance ofabnormalities of Treg in the pathogenesis of RA, we carried out the followingstudies. Our study consists of two sections: Section I:Studies of the expression level of Foxp3 in the RA patientsThis study explore the role of Treg in the immune pathogensis of RA bydetecting the level of Foxp3 mRNA, the Treg's specific marker, in PBMC ofRA patients in order to analyze the level of Treg of the RA patients。1.The expression level of Foxp3 in PBMC of the RA patientsThis study divides the patients into two groups: the RA-untreated groupwhich contains the patients who have never been treated byimmunosuppressive agents and/ or glucocorticoid in the past two years, andthe RA-treated group which contains the patients who have been treated byimmunosuppressive agents and/ or glucocorticoid continuously for more than4 months in the past 6 months. It shows that, both the RA-untreated group andthe RA-treated group have the expression level of Foxp3 in PBMC(1.70±1.17,3.85±3.25) much lower than the healthy control group (12.18±5.73),and that of the RA-untreated group is also lower than that of the RA-treatedgroup. The differences between groups show statistical significance( p<0.01). This indicates that the Treg level of RA patients may be reduced in thenumbers and/or functions.2.The relations between the expression level of Foxp3 and RA diseaseactivitiesIt is the very first time ever to analyze the correlation between theexpression level of Foxp3 in PBMC and several disease activity parameters ofRA, in order to probe the role of Treg in RA disease activity. The results ofthis study show that the RA patients' expression level of Foxp3 and DAS28,ESR have significant negative correlation (r=-0.459,p=0.001;r=-0.338,p=0.008, respectively). This indicates that the higher the disease activity of thepatient, the more severe reduction of Treg in the numbers and/or functions thepatient may have, which leads to the more severe arthritis of the patient. Itdemonstrates that, the RA patients' level of Treg may influence the patients'disease activity, and the reduction of Treg level may be one of the importantfactors that induce the RA active.3. The relations between the expression level of Foxp3 and variousclinical data of RA patientsThis study also analyzes the correlation between the RA patients'expression level of Foxp3and various clinical data (such as anti-CCP, RF anddisease duration), which has never been reported so far. This study shows thatthe expression level of Foxp3 in the patients' PBMC and anti-CCP serum levelhave significant negative correlation (r=-0.352,p=0.035). Since the serumconcentration of the anti-CCP and the RA disease duration, arthritis severityare closely related, combining the results of this study, it is reasonable tosuggest that the reduction of Treg in the numbers and/or functions maycorrelate with the development of the patient's disease, and also suggests thatthe RA patients' expression level of Foxp3 may be able to indicate thedevelopment of the patients' disease.4.The relations between the RA patients' expression level of Foxp3 andthe immunosuppressive treatmentThis study investigates the effect of the immunosuppressive agents and/or glucocorticoid on the expression level of Foxp3 in PBMC of RA patientsfor the first time, and found that the expression level of Foxp3 of the RApatients who were not treated by immunosuppressive treatment aresignificantly lower than that of the RA-treated group. It shows thatglucocorticoid and immunosuppressive agents can promote the production ofthe Treg, which may be one of the important function mechanisms of theimmunosuppressive treatment to prevent the development of the autoimmunedisease.Section II: Studies of Treg in collagen-induced arthritisTo further investigate the pathogenesis of RA, and to understand the roleof the Treg during RA initiation, this study adopts the RA animal model-CIArats as the research object. The level of Treg was examined using the FACSanalysis and realtime quantitative PCR during the various stages of the CIAinitiation and in various lymphoid organs of the rats, thus to thoroughlyunderstand the role of the Treg in the initiation and development of therheumatoid arthritis.1.The effect of the CII on the Treg level in CIA rats' peripheral lymphoidorgansThis study uses the realtime quantitative PCR and FACS to analyze theFoxp3 expression level and the frequency of CD4+CD25+ T cells in spleen andinguinal lymph nodes of the CIA rats after the onset of the disease. The resultsshow that, the Foxp3 expression level of spleen and inguinal lymph nodes andthe frequency of CD4+CD25+ T cells of the rats after the CIA onset aresignificantly lower than the control group. To further understand the role ofthe Treg in the CIA initiation, the Treg level of the rats which was treated byCII only once was also examined. The results show that, the Foxp3 expressionlevel in spleen and inguinal lymph nodes of the group treated by CII only onceare significantly lower than the control group, but significantly higher than theCIA group. It shows that, during the initiation of the CIA, the reduction of theTreg occurs before the emergency of the arthritis, indicating the important roleof the Trge abnormality in the pathogenesis of the CIA.2.The effect of the CII on the Treg level in CIA rats' thymusThis study also detects the Treg level in the rats' thymus during variousstages of CIA. It shows that, the Foxp3 expression level in thymus of the CIIimmunized once group is significantly lower than the control group, andsignificantly higher than the CIA group. Furthermore, the correlation analysisof the Foxp3 expression level and the frequency of CD4+CD25+ T cells indifferent lymphoid organs shows that both the Foxp3 expression level and thefrequency of CD4+CD25+ T cells in spleen and inguinal lymph nodes havesignificant positive correlation with the above results in thymus. The resultsshow that, CII first causes the reduction of the Treg in thymus of the rats, andresults in reduction of the Treg in peripheral lymphoid organs that cannotmaintain the normal immune tolerance, therefore leads to the initiation of CIA.It indicates that the decline of the Treg produced ability of the thymus may beone of the important factors of the CIA initiation.The innovation of this study is: (1) we found the significant reductionof the Foxp3 expression level in PBMC of RA patients for the first time,and the reduction has a negative correlation with the RA disease activity,at the same time, the immunosuppressive treatment can effectivelyincrease the Foxp3 expression level in PBMC of RA patients. It indicatesthat the Treg may be reduced in the numbers and/or functions in the RApatients, and the abnormalities of the Treg may be one of the importantfactors which cause the initiation of RA and its development. (2) Thisstudy also examines the change of the level of Treg in thymus, spleen andinguinal lymph nodes of the CIA rats in various stages of the disease forthe first time, especially the change of the level of Treg in thymus. Wefound that CII first causes the reduction of the ability of the thymus toproduce the Treg, therefore leads to the reduction of the Treg inperipheral lymphoid organs, and finally causes the CIA initiation. Thisstudy provides the experimental data for further investigating thepathogenesis of the RA and developing novel treatments for the disease.