MHC class II regulation and antigen processing in EAE

描述(由申请人提供)：MHC第二类调节对于了解多发性硬化症(MS)和实验性变态反应性脑脊髓炎(EAE)的抗原(Ag)提呈和CD4+T细胞激活至关重要。干扰素-γ(IFNGamma)是一种多效性细胞因子，被认为是非专业抗原提呈细胞(APC)包括常驻CNS APC诱导U类抗原提呈细胞所必需的。然而，缺乏干扰素的小鼠容易患上EAE。MHC-II类反式激活因子(CIITA)是干扰素-γ诱导的结构性II类基因表达的关键中间产物。CITA基因缺陷的小鼠对EAE具有抵抗力，这表明CNS炎症需要CITA依赖的第II类中枢APC的表达。CIITA在小胶质细胞表达II类分子中的作用尚不清楚，小胶质细胞是一种强大的中枢神经系统APC。CIITA还指导参与胞内抗原加工的不变链(II)和人类白细胞抗原-DM的表达。对II和H-2m缺陷小鼠和选择性表达II p31和p41的小鼠的研究表明，最初的CNS Ag提呈需要CNS APC的Ag加工，尽管这种可能性尚未直接测试。II p41可以稳定某些多肽，为抗原提呈提供了有利条件。Ii p31、p41和野生型小鼠对急性EAE的易感性相似，但Ii p41小鼠的病程更严重，提示Ii p41可能影响慢性EAE的抗原提呈。 本研究计划的主要目标是研究CIITA和Gamma干扰素II类表达的作用以及抗原加工在EAE中的作用。我们建议研究CIITA在CNS APC依赖的和非依赖的干扰素II类基因表达中的作用。我们推测，在体内，由小胶质细胞和巨噬细胞组成的CIITA导向的II类抗原表达将促进抗原提呈和EAE的发展，当CIITA导向的II类表达仅限于巨噬细胞和小胶质细胞时，仅由这些APC提呈抗原就足以在EAE中初始激活T细胞。我们推测，在最初的中枢神经系统抗原呈递过程中，银的加工是必需的，在慢性EAE期间，特定的II亚型可能会改变银的呈递。其具体目的是：(1)评估IFNGamma和IRF-1在CIITA对CNS APC诱导的Class II表达调控中的作用；(2)检测结构性CIITA如何引导小胶质细胞和巨噬细胞表达Class II影响中枢神经系统炎症的易感性；(3)通过使用II和H-2m缺陷小鼠构建的骨髓嵌合体小鼠，确定Ag加工在EAE中CNS抗原提呈中的作用；以及(4)通过对选择性表达II p31或p41的小鼠的分析，评估II亚型对慢性EAE严重程度的影响。这些研究将提供关于中枢神经系统II类调控的有价值的信息，这可能为开发调节MS的II类表达和T细胞激活的治疗手段提供洞察力。

DESCRIPTION (provided by applicant): MHC class II regulation is central in importance for understanding antigen (Ag) presentation and CD4 +T cell activation in multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). Interferon-gamma (IFNgamma), a pleiotropic cytokine, is considered a requirement for class U induction on nonprofessional Ag presenting cells (APC), including resident CNS APC. Yet, IFNgamma-deficient mice are susceptible to EAE. The MHC class II transactivator (CIITA) is a key intermediate in IFNgamma-inducible and constitutive class II expression. CIITA-deficient mice are resistant to EAE, indicating that CIITA-dependent class II expression by resident CNS APC is required for CNS inflammation. The in vivo role of CIITA in class II expression by microglia, a potent CNS APC, is not known. CIITA also directs expression of invariant chain (Ii) and HLA-DM, molecules involved in endocytic Ag processing. Studies of Ii and H-2M deficient mice and mice that selectively express Ii p31 and p41 suggest that Ag processing by CNS APC is required for initial CNS Ag presentation, although this possibility has not been tested directly. Ii p41 may stabilize certain peptides, providing advantage in Ag presentation. Ii p31, p41 and wild-type mice are similarly susceptible to acute EAE, but Ii p41 mice have a more severe course, suggesting that Ii p41 may influence Ag presentation in chronic EAE. The principle goals of this research program are to investigate the role of CIITA and gammaIFN class II expression and the role of Ag processing in EAE. We propose to examine the role of CIITA in IFNgamma-dependent and IFN(-independent class II expression by CNS APC. We hypothesize that constitutive CIITA-directed class II by microglia and macrophages in vivo will promote Ag presentation and EAE development, and that when CIITA-directed class II expression is restricted to macrophages and microglia, Ag presentation by these APC alone will be sufficient for initial T cell activation in EAE. We hypothesize that Ag processing is required for initial CNS Ag presentation and that the particular Ii isoform may alter Ag presentation during chronic EAE. The Specific Aims are to: (1) evaluate the role of IFNgamma and IRF-1 on CIITA regulation on class II expression by CNS APC, (2) examine how constitutive CIITA directed class II expression by microglia and macrophages influences susceptibility to CNS inflammation, (3) determine the role of Ag processing in CNS Ag presentation in EAE through use of bone marrow chimera mice constructed from Ii and H-2M deficient mice, and (4) to evaluate how the Ii isoform influences chronic EAE severity through analysis of mice that selectively express Ii p31 or p41. These studies will provide valuable information regarding CNS class II regulation, which may provide insight for development of therapeutic means to modulate class II expression and T cell activation in MS.