Differential activation of astrocytes by innate and adaptive immune stimuli

The immunologic privilege of the central nervous system (CNS) makes it crucial that CNS resident cells be capable of responding rapidly to infection. Astrocytes have been reported to express Toll-like receptors (TLRs), hallmark pattern recognition receptors of the innate immune system, and respond to their ligation with cytokine production. Astrocytes have also been reported to respond to cytokines of the adaptive immune system with the induction of antigen presentation functions. Here we have compared the ability of TLR stimuli and the adaptive immune cytokines interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) to induce a variety of immunologic functions of astrocytes. We show that innate signals LPS- and poly I:C lead to stronger upregulation of TLRs and production of the cytokines IL-6 and TNF-alpha as well as innate immune effector molecules IFN-alpha4, IFN-beta, and iNOS compared with cytokine-stimulated astrocytes. Both innate stimulation and adaptive stimulation induce similar expression of the chemokines CCL2, CCL3, and CCL5, as well as similar enhancement of adhesion molecule ICAM-1 and VCAM-1 expression by astrocytes. Stimulation with adaptive immune cytokines, however, was unique in its ability to induce upregulation of MHC II and the functional ability of astrocytes to activate CD4(+) T cells. These results indicate potentially important and changing roles for astrocytes during the progression of CNS infection.     

Inhibition of LFA-1/ICAM-1 and VLA-4/VCAM-1 as a therapeutic approach to inflammation and autoimmune diseases

This review focuses on providing insights into the structural basis and clinical relevance of LFA-1 and VLA-4 inhibition by peptides and small molecules as adhesion-based therapeutic strategies for inflammation and autoimmune diseases. Interactions of cell adhesion molecules (CAM) play central roles in mediating immune and inflammatory responses. Leukocyte function-associated antigen (LFA-1, alpha(L)beta(2), and CD11a/CD18) and very late antigen (VLA-4, alpha(4)beta(1), and CD49d/CD29) are members of integrin-type CAM that are predominantly involved in leukocyte trafficking and extravasation. LFA-1 is exclusively expressed on leukocytes and interacts with its ligands ICAM-1, -2, and -3 to promote a variety of homotypic and heterotypic cell adhesion events required for normal and pathologic functions of the immune systems. VLA-4 is expressed mainly on lymphocyte, monocytes, and eosinophils, but is not found on neutrophils. VLA-4 interacts with its ligands VCAM-1 and fibronectin (FN) CS1 during chronic inflammatory diseases, such as rheumatoid arthritis, asthma, psoriasis, transplant-rejection, and allergy. Blockade of LFA-1 and VLA-4 interactions with their ligands is a potential target for immunosuppression. LFA-1 and VLA-4 antagonists (antibodies, peptides, and small molecules) are being developed for controlling inflammation and autoimmune diseases. The therapeutic intervention of mostly mAb-based has been extensively studied. However, due to the challenging relative efficacy/safety ratio of mAb-based therapy application, especially in terms of systemic administration and immunogenic potential, strategic alternatives in the forms of peptide, peptide mimetic inhibitors, and small molecule non-peptide antagonists are being sought. Linear and cyclic peptides derived from the sequences of LFA-1, ICAM-1, ICAM-2, VCAM-1, and FN C1 have been shown to have inhibitory effects in vitro and in vivo. Finally, understanding the mechanism of LFA-1 and VLA-4 binding to their ligands has become a fundamental basis in developing therapeutic agents for inflammation and autoimmune diseases.     

Neutrophils influence melanoma adhesion and migration under flow conditions

We have studied human melanoma cell (C8161) adhesion and migration in response to stimulation by soluble collagen IV (CIV) using a modified Boyden chamber. In this modified chamber, shear flow can be introduced over the cell-substrate interface, affecting tumor cell chemotactic migration through a microporous filter. A relatively high level of intercellular adhesion molecule-1 (ICAM-1) was found on C8161 cells. In contrast, levels of beta(2)-integrins (e.g., LFA-1 and Mac-1), the molecules that would be necessary for C8161 stable adhesion to the endothelium substrate, were found to be very low on these melanoma cells. As a result, C8161 transendothelial migration under a flow condition of 4 dyn/cm(2) decreased by 70% as compared to static migration. When human neutrophils (PMNs) were present in the tumor cell suspension, C8161 migration recovered by 85% over C8161 cells alone under the 4 dyn/cm(2) flow condition. Blocking ICAM-1 on C8161 cells or Mac-1 on PMNs significantly inhibited C8161-PMN adhesion and subsequent C8161 migration through the endothelium under flow conditions. In addition, increased interleukin-8 production and Mac-1 expression by PMNs were detected when they were co-cultured with C8161 melanoma cells. These results suggest that transmigration of C8161 cells under flow conditions can be influenced by PMNs, mediated by Mac-1/ICAM-1 adhesive interactions and enhanced by altered cytokine production.     

The red cell LW blood group protein is an intercellular adhesion molecule which binds to CD11/CD18 leukocyte integrins

Leukocyte adhesion involves the leukocyte-specific integrins CD11a/CD18, CD11b/CD18 and CD11c/CD18, which bind to intercellular adhesion molecules (ICAM). Three ICAM have been described, and are expressed on leukocytes and various other cells, but are absent from red cells. Here, we show that the red cell Landsteiner-Wiener (LW) blood group glycoprotein is an ICAM which binds to the leukocyte-specific integrins. This finding has important implications in red cell physiology.     

Triamcinolone acetonide modulates permeability and intercellular adhesion molecule-1 (ICAM-1) expression of the ECV304 cell line: implications for macular degeneration

Whilst animal studies and a pilot clinical trial suggest that intravitreal triamcinolone acetonide (TA) may be useful in the treatment of age-related macular degeneration (AMD), its mode of action remains to be fully elucidated. The present study has investigated the capacity of TA to modulate the expression of adhesion molecules and permeability using a human epithelial cell line (ECV304) as a model of the outer blood-retinal barrier (BRB). The influence of TA on the expression of ICAM-1 and MHC-I was studied on resting and phorbol myristate acetate (PMA)- or interferon-gamma (IFN-gamma)- and/or tumour necrosis factor-alpha (TNF-alpha)-activated cells using flow cytometry and immunocytochemistry. Additionally, ECV304 cells were grown to confluence in uncoated Transwell chambers; transepithelial resistance (TER) across resting and PMA-activated cells was monitored. TA significantly decreased the paracellular permeability of ECV304 cells and down-regulated ICAM-1 expression, consistent with immunocytochemical observations. PMA-induced permeability changes were dose-dependent and TA decreased permeability of both resting and PMA-activated monolayers. MHC-I expression by ECV304 cells however, was not significantly affected by TA treatment. The modulation of TER and ICAM-1 expression in vitro correlate with clinical observations, suggesting re-establishment of the BRB and down-regulation of inflammatory markers are the principal effects of intravitreal TA in vivo. The results further indicate that TA has the potential to influence cellular permeability, including the barrier function of the retinal pigment epithelium (RPE) in AMD-affected retinae.     

ICAM‐1 and β3 integrin immunoexpression in malignant melanoma cells: can they be used as additional predictors?

Malignant melanoma usually progresses from the intraepidermal microenvironment through a distinct radial growth phase, in which malignant potential cannot always be accurately evaluated, to invasion of the dermis (vertical growth phase) and metastasis. During these stages malignant cells interact with each other and with the extracellular matrix. This interaction is mediated by cell surface adhesion molecules such as the beta(3) integrin subunit and ICAM-1. Our aim was to investigate whether the expression of these two molecules is associated with the various histopathologic prognosticators commonly evaluated in malignant melanoma. Using a standard three-step immunoperoxidase technique we evaluated the above molecules' expression in a documented series of 66 cutaneous malignant melanomas. Forty-five were superficial spreading melanomas, including 18 in mixed growth phase. Positive immunoreaction was estimated by image analysis. ICAM-1 immunopositivity status was significantly more frequent among malignant melanomas of the nodular type (p=0.0001), and was associated with the vertical growth phase, Breslow thickness of >0.77 mm, and with evident lymphocytic infiltration. beta(3) integrin immunopositivity showed similar results in certain respects; it was more frequently detected in superficial spreading melanomas in which vertical growth had developed (p=0.002) and in cases with regression. There appears to be an association of these molecules with histopathologic features that predict increased tumorigenicity of malignant melanocytes.     

B7/CD28和ICAM-1/LFA-1共刺激信号对T及B细胞功能影响的研究

目的　研究共刺激途径Ｂ７／ＣＤ２８ 和ＩＣＡＭ１／ＬＦＡ１ 对Ｔ 细胞活化以及Ｂ 细胞效应的作用。方法　在体外建立ＡＰＣＴＢ 细胞反应系统, 用Ｂ７１ 单抗和ＩＣＡＭ１ 单抗分别阻断Ｂ７／ＣＤ２８ 和ＩＣＡＭ１／ＬＦＡ１ 共刺激途径, 利用３ ＨＴｄＲ 法检测Ｔ 细胞增殖,ＥＬＩＳＡ 法测定Ｂ 细胞分泌的抗体, 用ＲＴＰＣＲ 法检测细胞因子基因的表达。结果　Ｂ７１ 单抗和ＩＣＡＭ１ 单抗均可抑制Ｔ 细胞增殖及ＩＬ２ 的产生。Ｂ７１ 单抗可下调Ｂ 细胞抗体的产生（ Ｐ＜ ０ ．０５） , 而ＩＣＡＭ１ 单抗未见明显的抑制（ Ｐ＞ ０ ．０５） 。Ｂ７１ 单抗和ＣｓＡ 联用能阻断Ｔ 细胞增殖活性及Ｂ 细胞的效应, 而ＩＣＡＭ１ 单抗和ＣｓＡ联用则无此作用。Ｂ７１ 单抗能下调ＩＬ２ 和ＩＦＮγｍ ＲＮＡ 表达,Ｂ７１ 单抗和ＣｓＡ 联用则阻断ＩＬ２ 和ＩＦＮγｍ ＲＮＡ 表达,ＩＬ４ 和ＩＬ１０ ｍ ＲＮＡ 仍可表达。结论　Ｂ７／ＣＤ２８ 和ＩＣＡＭ１／ＬＦＡ１ 共刺激途径在Ｔ 细胞活化中具有不同的作用,Ｂ７１ 单抗和ＣｓＡ 联用可导致Ｔ 细胞功能失活即无能。     

血管紧张素II对单核细胞趋化因子及粘附分子表达的影响

为了观察血管紧张素II (AII)对人单核细胞株THP 1分泌单核细胞趋化因子 (MCP 1)、人类脐静脉内皮细胞(HUVEC )分泌细胞间粘附分子 (ICAM 1)的影响及AII对HUVEC与THP 1的粘附功能的影响 ,我们利用ELISA法检测AII作用后THP 1分泌MCP 1及HUVEC分泌ICAM 1的表达 ,利用计数法观察经AII作用的HUVEC与THP 1的粘附率。结果发现四种不同浓度的AII(10 6、 10 7、 10 8、 10 9mol/L )刺激THP 1及HUVEC 2 4h后 ,MCP 1及ICAM 1的分泌明显增加 ,AII(10 6mol/L )作用HUVEC 6h后 ,其对THP 1细胞粘附率明显增加 ,表明AII具有调节THP 1分泌MCP 1及HUVEC分泌ICAM 1的作用 ,AII可通过致炎症作用参与动脉粥样硬化的发病过程。