Cytokines And Growth Factors In Autoimmune Diseases

TGF-β是一种多功能免疫调节剂，具有免疫抑制和促炎作用。TGF-β协调对炎症反应的进展和消退至关重要的事件。这种复杂的协调涉及炎症细胞的募集、淋巴细胞的活化、巨噬细胞功能的调节以及内皮细胞、单核细胞和淋巴细胞表达粘附分子。在哺乳动物中发现的三种同种型中，TGF-β 1是影响这些体内免疫功能的主要同种型。因此，在我们的小鼠中靶向破坏TGF-β 1基因导致以进行性多灶性炎症为特征的致死表型并不意外。我们以前已经确定了这种复杂的免疫失调的分子机制。我们进一步证明，超过一半的无效小鼠在子宫内死亡，这种胚胎致死性与胚胎卵黄囊中早期造血和血管系统的缺陷有关。活产TGF-β 1基因敲除小鼠早在出生后第7天就表现出炎症发作，这与两类MHC分子的表达增强和白细胞与血管内皮的粘附增加一致。在随后的分析中，我们发现无效小鼠也表现出自身免疫表现，如核抗原抗体水平升高和免疫复合物的肾脏沉积。我们还证明，这种自身免疫表型可以通过骨髓移植的骨髓细胞从空小鼠到致死辐射的野生型小鼠。有趣的是，我们的研究与纤维连接蛋白的细胞和肝素结合序列相对应的合成肽表明其对无效小鼠的改善作用，特别是在减少淋巴细胞对血管内皮的粘附和减少唾液腺和泪腺中的炎症。增强表达的MHC-I类和- II类抗原在TGF-β 1基因敲除小鼠表明，这两种抗原在这些小鼠的自身免疫反应的发展中具有重要作用。随后，我们通过产生TGF-β 1/MHC-II双无效小鼠来表征MHC-II类抗原的作用。这些小鼠没有任何炎性浸润、循环自身抗体或肾小球免疫复合物沉积的证据。相反，这些小鼠表现出髓外造血，存活时间略长于TGF-β 1基因敲除小鼠。因此，MHCII类抗原对于TGF-β 1缺失小鼠中自身免疫的表达是必需的，并且通常可以与该生长因子合作来调节造血。为了阐明MHC I类分子在TGF-β 1基因敲除小鼠发病机制中的确切作用，我们在MHC I类/？2-微球蛋白（？2 M）缺陷。? 2 M null小鼠缺乏MHC I类抗原和外周CD 8 + T细胞的表达，因为？2 M对于重链和轻链的MHC I类异二聚体的正确组装、转运和细胞表面表达是必需的。Kaplan-Meier分析显示TGF-β 1/β 2 M双缺失小鼠的存活率显著改善。虽然炎性病变的组织分布与TGF-β 1缺失小鼠中发现的相似，但双缺失小鼠中炎症的严重程度显著降低，尤其是在心脏中。流式细胞术分析显示胸腺、脾脏和淋巴结中的CD 8 + T细胞水平降低，表明胸腺中的T细胞发育受损。这些小鼠还表现出骨髓生成增加，炎症减少。此外，这些小鼠的循环自身抗体和肾小球免疫复合物沉积水平显著降低。因此，这些结果表明，MHC I类分子影响TGF-β 1缺失小鼠中观察到的自身免疫和炎症的发展，并且CD 8 + T细胞可能有助于这些小鼠中的炎症。为了评估活性TGF-β 1循环水平的治疗潜力，我们产生了小鼠内分泌表达的活性TGF-β 1的TGF-β 1空背景（TGF-β 1（-/-/TG））通过交叉TGF-？1（+/-）小鼠与转基因小鼠（TG）表达TGF-？1在肝脏中，并在血液中分泌。TGF-b1（-/-/TG）小鼠表现出与TGF-b1（-/-）小鼠相似的存活曲线，表明未能挽救致死表型。血清TGF-？TGF-β_1（-/-/TG）小鼠体内TGF-β_1的表达水平恢复到正常水平，在所有组织中均有表达，尤其是在肾脏和脾脏。组织学显示所有靶组织的炎症减少，特别是心脏。有趣的是，与TGF-b（-/-）小鼠不同，TGF-b1（-/-/TG）小鼠在其肾脏中具有与TG小鼠相似的肾小球肾炎。因此，TGF-β 1（-/-/TG）动物模型的表型表明循环活性TGF-β 1的潜在作用？1在减少炎症，但它未能挽救在TGF-？1 null小鼠表明自分泌TGF-？1. 目前，正在研究TGF-β亚型的亚型特异性作用，并将其表达靶向特定的细胞类型。

TGF-beta is a multifunctional immunomodulator with immunosuppressive as well as proinflammatory actions. TGF-beta coordinates events critical to the progression and resolution of inflammatory responses. This complex coordination involves recruitment of inflammatory cells, activation of lymphocytes, modulation of macrophage function, and expression of adhesion molecules by endothelial cells, monocytes, and lymphocytes. Of the three isoforms found in mammals, TGF-beta1 is the predominant isoform that affects these immune functions in vivo. Therefore, it was not unexpected that the targeted disruption of the TGF-beta1 gene in our mice resulted in a lethal phenotype characterized by progressive multifocal inflammation. We had previously identified some of the molecular mechanisms underlying this complex immune dysregulation. We further demonstrated that more than half of the null mice die in utero, and that this embryonic lethality is associated with defects in early hematopoiesis and vasculature in the embryonic yolk sac. Live-born TGF-beta1 null mice exhibit onset of inflammation as early as postnatal day 7, coincident with enhanced expression of both classes of MHC molecules and increased adhesion of leukocytes to the vascular endothelium. In subsequent analyses, we found that the null mice also exhibit autoimmune manifestations such as elevated levels of antibodies to nuclear antigens and kidney deposits of immune complexes. We have also demonstrated that this autoimmune phenotype can be transferred by bone marrow transplantation of bone marrow cells from the null mice to lethally-irradiated wild-type mice. Interestingly, our studies with the synthetic peptides corresponding to cell- and heparin-binding sequences of fibronectin indicate their ameliorating effects on the null mouse, especially in reducing the adhesion of lymphocytes to the vascular endothelium and reducing inflammation in the salivary and lachrymal glands. Enhanced expression of MHC class -I and- II antigens in TGF-beta1 null mice suggested that both of these antigens have important roles in the development of the autoimmune reactions in these mice. We subsequently characterized the role of MHC class II antigens by generating TGF-beta1/MHC-II double null mice. These mice are without any evidence of inflammatory infiltrates, circulating autoantibodies or glomerular immune complex deposits. Instead, these mice exhibit extramedullary hematopoiesis and survive slightly longer than the TGF-beta1 null mice. Thus, MHC class II antigens are essential for the expression of autoimmunity in the TGF-beta1 null mice and may normally cooperate with this growth factor to regulate hematopoiesis. To delineate the precise role of MHC class I molecules in the pathogenesis of TGF-beta1 null mice, we generated TGF-beta1 null mice in the genetic background of MHC class I/?2-microglobulin (?2M) deficiency. ?2M null mice lack expression of MHC class I antigen and peripheral CD8+ T cells because ?2M is essential for the proper assembly, transport and cell surface expression of the MHC class I heterodimers of heavy and light chains. Kaplan-Meier analysis showed a significant improvement in survival of the TGF-beta1/beta2M double null mice. While the tissue distribution of inflammatory lesions was similar to that found in TGF-beta1 null mice, the severity of inflammation was significantly reduced in the double null mice, especially in the heart. Flow cytometric analysis revealed reduced levels of CD8+ T cells in the thymus, spleen and lymph node, suggesting impaired T cell development in thymus. These mice also exhibited increased myelopoiesis with decreased inflammation. Moreover, these mice had significantly reduced levels of circulating autoantibodies and glomerular immune complex deposits. These results thus indicate that MHC class I molecules influence the development of the autoimmunity and inflammation seen in TGF-beta1 null mice, and CD8+ T cells may contribute to the inflammation in these mice. To assess the therapeutic potential of circulating levels of active TGF-b1, we generated mice with endocrine expression of active TGF-b1 on a TGF-b1 null background (TGF-b1(-/-/TG)) by crossing TGF-?1(+/-) mice with transgenic mice (TG) that express TGF-?1 in liver and secrete in the blood. The TGF-b1(-/-/TG) mice exhibit a survival profile similar to the TGF-b1 (-/-) mice indicating a failure to rescue lethal phenotype. However, serum TGF-?1 levels in theTGF-b1 (-/-/TG) mice were restored to normal level, with expression in all the tissues notably in the kidney and spleen. Histopathology showed reduced inflammation in all target tissues, especially in the heart. Interestingly unlike TGF-b (-/-) mice, the TGF-b1(-/-/TG) mice have glomerulonephritis in their kidneys similar to the TG mice. Thus, the phenotype of TGF-b1 (-/-/TG) animal model indicates the potential role of circulating active-TGF-?1 in reducing inflammation but it failure to rescue lethality in TGF-?1 null mice indicates critical role of autocrine TGF-?1. Currently, work is underway to study isform specific role of TGF-beta isoforms and also to target its expression to specific cell types.