The mechanism by which tolerance is induced via systemic administration of high doses of aqueous antigen has been analyzed by using mice transgenic for a T-cell receptor specific for the influenza virus hemagglutinin (HA) peptide comprising amino acids 126-138. After intravenous injection of 750 (but not 75) ,ug of HA peptide, a state of hyporesponsiveness was rapidly induced. In the thymus, in situ apoptosis in the cortex and at the corticomedullary junction was responsible for a synchronous and massive deletion of CD4+ CD8+ thymocytes. In secondary lymphoid organs, HA-reactive T cells were initially activated but were hyporesponsive at the single cell level. After 3 days, however, those cells were rapidly deleted, at least partially, through an apoptotic process. Therefore, both thymic and peripheral apoptosis, in addition to T-cell receptor desensitization, contribute to high-dose tolerance.T-cell tolerance to self antigens is acquired through both thymic and peripheral events. In the thymus, developing T cells are clonally deleted or, in some instances, anergized upon encountering their specific major histocompatibility complex (MHC)-self peptide ligands (1, 2). Nevertheless, some autoreactive T cells do enter the periphery and several mechanisms normally operate to prevent these autoreactive T cells from initiating an autoimmune disease. These mechanisms have been studied extensively in recent years, particularly in systems using mice transgenic for neo-self antigens expressed in a tissue-specific manner and/or using mice transgenic for the T-cell receptor (TCR). By using this technology, evidence for peripheral self tolerance through anergy (3), modulation of TCR and coreceptor molecule expression (2), clonal deletion (2), and clonal diversion (4) MATERIALS AND METHODSMice. The HNT-TCR transgenic mice were generated as described (4). For this study, one line, in which '50 copies of the TCR a transgene and 40 copies of the TCR 3 transgene had integrated in the same chromosomal location, was backcrossed at least five times on the B10.D2 (H-2d)

Knowing the autoantigen target(s) in an organ-specific autoimmune disease is essential to understanding its pathogenesis. Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease characterized by lymphocytic infiltration of the islets of Langerhans (insulitis) and destruction of insulin-secreting pancreatic beta-cells. Several beta-cell proteins have been identified as autoantigens, but their importance in the diabetogenic process is not known. The non-obese diabetic (NOD) mouse is a murine model for spontaneous IDDM. Here we determine the temporal sequence of T-cell and antibody responses in NOD mice to a panel of five murine beta-cell antigens and find that antibody and T-cell responses specific for the two isoforms of glutamic acid decarboxylase (GAD) are first detected in 4-week-old NOD mice. This GAD-specific reactivity coincides with the earliest detectable response to an islet extract, and with the onset of insulitis. Furthermore, NOD mice receiving intrathymic injections of GAD65 exhibit markedly reduced T-cell proliferative responses to GAD and to the rest of the panel, in addition to remaining free of diabetes. These results indicate that the spontaneous response to beta-cell antigens arises very early in life and that the anti-GAD immune response has a critical role in the disease process during this period.

IDDM is a T-cell-mediated autoimmune disease in which the insulin-producing beta-cells are destroyed. The disease process is complex, involving the recognition of several beta-cell autoantigens. One of these, GAD65, appears to have a critical and not fully defined role in IDDM in humans and in the NOD mouse. We provide evidence that an ongoing diabetogenic response in NOD mice can be suppressed after intravenous administration of GAD65, but not by other beta-cell autoantigens. Furthermore, suppression of the diabetogenic response is mediated by the induction of GAD65-specific CD4+ regulatory T-cells. Finally, cytokine analysis indicates that these CD4+ regulatory T-cells have a T-helper 2 phenotype.

The correlation between immunity and Parkinson's disease was presented in many papers, which also discussed lymphocyte and natural killer cell. But these studies have yielded inconsistent results. To systematically review the relationship between the lymphocyte subsets/natural killer cell and the risk of Parkinson's disease, we electronically searched the SpringerLink, Web of Science, Ebsco-medline with full text, Pubmed, Elsevier-ScienceDirect, Ovid-lww-oup, Wanfang Data for case-control trials on comparing the number of peripheral blood lymphocyte subsets and natural killer cell in Parkinson's patients and healthy controls. According to the Cochrane methods, the reviewers selected literature, extracted data, and assessed the quality. Then, a meta-analysis was performed using RevMan 5.2. Finally, 21 case-control trials including 943 cases of Parkinson's disease were fit into our data analysis. Meta-analysis showed that the decreased numbers of CD3+, CD4+ lymphocyte subsets and the increased number of natural killer cell were found in Parkinson's disease patients. In the intermediate and late stage of PD, CD8+ lymphocyte subsets had a significant decrement. However, the number of B lymphocyte subsets had no significant association with Parkinson's disease. The lymphocyte subsets and NK cell may be associated with the risk of Parkinson's disease.