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[The onset mechanism of experimental autoimmune uveoretinitis induced by interphotoreceptor retinoid-binding protein].

In order to analyze the onset mechanism of experimental autoimmune uveoretinitis (EAU), two experimental models were used; one was EAU induced by one injection of purified bovine interphotoreceptor retinoid-binding protein (IRBP) with complete Freund's adjuvant in Lewis rat, and the other was an IRBP-induced autoimmune uveoretinitis that occurred spontaneously in nude (nu/nu) mice at 4 weeks of age reconstituted by the grafting of rat embryonic thymus (TG nude mouse). EAU develops when the IRBP-reactive lymphocytes in the regional lymph-nodes are activated. Activation begins when the T lymphocyte recognizes the peptide for the epitope bound to a major histocompatibility complex (MHC) molecule in the antigen-presenting cell by way of the T-cell receptor (TCR). In EAU, ten peptide residues p1182-1191 of the IRBP amino acid sequence, were revealed to be sufficiently capable of lymphocyte activation for EAU, and it was also shown that amino acid positions 1182W (tryptophane), 1185G (glycine), 1186V (valine) and 1188P (proline) of IRBP play important roles as the epitopes or agretopes in developing EAU. On the other hand, two amino acids of IRBP, amino acid positions 1182W (tryptophane) and 1194P (proline) were shown to be the agretopes inducing autoimmune uveoretinitis in the TG nude mouse. A study of the variable region of the TCR with a residual p1182-1194 specific T-cell line from the TG nude mouse revealed that as many as 96% utilized the T-cell receptor V beta 6 gene and that the peptide-MHC molecule complex was recognized by restricted receptors. Adhesion molecules such as ICAM-1 and LFA-1 were also found to play an important role as cofactors in activation of lymphocytes in the antigen-recognition process of EAU. Uveoretinitis seemed to result from an immune reaction in the eye occurring when the T lymphocyte arrives there, activating the immunological process. ICAM-1 and LFA-1 were also found to be involved in the infiltration process of inflammatory cells: our immunohistological examination revealed that ICAM-1 was present in the retinal pigment epithelium and epithelium of the ciliary body composing the blood-ocular barrier. In contrast, LFA-1 was expressed in the infiltrating cells. Finally, the tolerance of IRBP was discussed and it was experimentally demonstrated that the absence of IRBP-induced uveoretinitis in human beings and certain experimental animals resulted from endogenous IRBP serving as a tolerogen; we assumed that the breakdown of this self-tolerance would induce EAU due to thymic dysfunction or IRBP antigen injection.

Amino Acid Sequence↗

[Adhesion of lymphocytes to allogenic endothelium. Four different pathways].

Lymphocyte adhesion to allogeneic endothelium is a critical step in graft rejection. To further characterize the expression and the regulation of adhesion molecules involved in this process, we stimulated endothelial cells with Interleukin 4 or tumor necrosis factor alpha (TNF alpha) and blocked lymphocyte adhesion to stimulated-endothelial cells with monoclonal antibodies. We demonstrated that lymphocytes bound endothelial cells by at least four adhesion pathways: a) a LFA 1/ICAM 1 dependent pathway on TNF alpha-stimulated endothelial cells, b) a LFA 1 dependent/ICAM 1 independent pathway on unstimulated or IL 4-stimulated endothelial cells, c) a VLA 4/VCAM 1 dependent pathway on unstimulated and stimulated-endothelial cells, d) a CD 2 dependent/LFA 3 independent pathway on IL 4 and TNF alpha-stimulated endothelial cells.

Antibodies, Monoclonal↗

Frequency of common colds and serum levels of sICAM-1 (CD54), sLFA-3 (CD58) and sIL-2R (CD25).

Epidemiologic case-control studies have suggested an inverse relationship between past medical history of frequency of common colds and subsequent cancer risk for various sites. One hypothetical explanation for this finding may be that there are unknown differences in immune responsiveness between patients developing cancer and healthy individuals. The present study examines the relationship between the frequency of common colds and a) plasma levels of sICAM-1/CD54, sLFA-3/CD58 and sIL-2R/CD25 which are believed to modulate activation of immune responses, and b) cell-mediated immunity in vivo as determined by Multitest Mérieux. The investigation was conducted as a correlation study amongst a healthy group of individuals from the general population in Germany. We found a statistically significant inverse relationship between frequency of common colds and levels of sCD58 and, partially, sCD54. No association was found between levels of sCD25 and results of Multitest Mérieux.

Aged↗

On the immunopathology of multiple sclerosis lesions.

Active chronic multiple sclerosis (MS) lesions contain numerous T-200 and leukocyte function associated antigen (LFA)-1-positive infiltrating cells. Macrophages at the lesion edge are stained for immunoglobulins (Ig), Class I and Class II major histocompatibility complex (MHC) antigens, for interferon (IFN)-alpha and for the beta-2 integrin adhesion molecule gp 150/95. In the periplaque area, numerous CD2, CD4, and CD8 positive T cells and cells reactive for the CD45RO phenotype of memory cells and for gamma/delta T cell receptors are located between MHC-positive glial cells. White matter at the edge is diffusely stained for intercellular adhesion molecule (ICAM)-1 and LFA-3. Remote from lesions, labeling for Class II MHC, ICAM-1 and LFA-3 was enhanced on some endothelial and glial cells. These findings indicate that adhesion molecules are involved in the formation and possibly also in the reactivation of MS lesions.

Antigens, CD↗

Impairment of lymphocyte adhesion to cultured fibroblasts and endothelial cells by gamma-irradiation.

A critical component of immune responsiveness is the localization of effector cells at sites of inflammatory lesions. Adhesive molecules that may play a role in this process have been described on the surfaces of both lymphocytes and connective tissue cells. Adhesive interactions of T lymphocytes with fibroblasts or endothelial cells can be inhibited by preincubation of the fibroblasts or endothelial cells with antibody to intercellular adhesion molecule 1 (CD54) or by preincubation of the T cells with antibody to lymphocyte function-associated Ag 1 (CD11a/CD18), molecules shown to be important in several other cell-cell adhesive interactions. Here we show that gamma-irradiation of human T lymphocytes impaired their ability to adhere to both fibroblasts and endothelial cells. This impairment was not associated with a loss of cell viability or of cell surface lymphocyte function-associated Ag 1 expression. gamma-Irradiation of T cells is known to result in the activation of ADP-ribosyltransferase, an enzyme involved in DNA strand-break repair, causing subsequent depletion of cellular nicotinamide adenine dinucleotide (NAD) pools by increasing NAD consumption for poly(ADP-ribose) formation. Preincubation of T cells with either nicotinamide or benzamide [corrected], both known inhibitors of ADP-ribosyltransferase, completely reversed the suppressive effects of gamma-irradiation on T cell adhesion. The maintenance of adhesion was accompanied by inhibition of irradiation-induced depletion of cellular NAD. These experiments suggest that the impairment of cellular immune function after irradiation in vivo may be caused, in part, by defective T cell emigration and localization at inflammatory sites.

Adenosine Triphosphate↗

Intercellular adhesion molecule-2, a second counter-receptor for CD11a/CD18 (leukocyte function-associated antigen-1), provides a costimulatory signal for T-cell receptor-initiated activation of human T cells.

Activation of T cells often requires both activation signals delivered by ligation of the TCR and those resulting from costimulatory interactions between certain T cell surface accessory molecules and their respective counter-receptors on APC. CD11a/CD18 complex on T cells modulate the activation of T cells by interacting with its counter-receptors intracellular adhesion molecule (ICAM-1) (CD54) and/or ICAM-2 on the surface of APC. The costimulatory ability of ICAM-1 has been demonstrated. Using a soluble ICAM-2 Ig fusion protein (receptor globulin, Rg) we demonstrate the costimulatory effect of ICAM-2 during the activation of CD4+ T cells. When coimmobilized with anti-TCR-1 mAb ICAM-2 Rg induced vigorous proliferative response of CD4+ T cells. This costimulatory effect of ICAM-2 was dependent on its coimmobilization with mAb directed at the CD3/TCR complex but not those directed at CD2 or CD28. Both resting as well as Ag-primed CD4+ T cells responded to the costimulatory effects of ICAM-2. The addition of mAb directed at the CD11a or CD18 molecules almost completely inhibited the responses to ICAM-2 Rg. These results are consistent with the role of CD11a/CD18 complex as a receptor for ICAM-2 mediating its costimulatory effects. Stimulation of T cells with coimmobilized anti-TCR-1 and ICAM-2 resulted in the induction of IL-2R (CD25), and anti-Tac (CD25) mAb inhibited this response suggesting the contribution of endogenously synthesized IL-2 during this stimulation. These results demonstrate that like its homologue ICAM-1, ICAM-2 also exerts a strong costimulatory effect during the TCR-initiated activation of T cells. The costimulatory effects generated by the CD11a/CD18:ICAM-2 interaction may be critical during the initiation of T cell activation by ICAM-1low APC.

Antigen-Presenting Cells↗

Regulation of ICAM-1 expression and function in human dermal fibroblasts by IL-4.

ICAM-1 is found on the surface of many hematopoietic and nonhematopoietic cells and can function as an adhesive ligand for the integrin, leukocyte function-associated molecule-1 (LFA-1, CD11a/CD18). ICAM-1/leukocyte function-associated molecule-1 interaction has been shown to be of importance in many immune-mediated cell-cell adhesion reactions. In vitro, unstimulated human fibroblast cell cultures express low levels of ICAM-1. Using ELISA, cytofluorography, electron microscopy, Northern analysis, and an in vitro cell adherence assay, we demonstrate that treatment of human dermal fibroblasts with the cytokine IL-4 leads to an increase in cell surface ICAM-1 expression that is under transcriptional control as well as increased fibroblast adhesion to LFA-1-bearing T lymphocytes. The kinetics of increased ICAM-1 expression induced by IL-4 paralleled the increase in ICAM-1-dependent T lymphocyte adhesion. The increase in T cell adhesion was determined to be due to the effects of IL-4 on the fibroblasts and not the adhering T cells. Treatment of fibroblasts with IL-4 also resulted in enhanced binding of human rhinovirus, a recently reported additional ligand for ICAM-1. Virus binding was IL-4 dose dependent and could be inhibited with mAb to ICAM-1. Both the expression of ICAM-1 and the ICAM-1-dependent increase in T lymphocyte adhesion that was induced by IL-4 could be inhibited by preexposure of the fibroblasts to either IL-1 or IL-6, suggesting that multiple cytokines can have both positive and negative effects on human fibroblast ICAM-1 expression and function.

Cell Adhesion↗

Deletion of antigen-specific immature thymocytes by dendritic cells requires LFA-1/ICAM interactions.

An in vitro assay was used for assessing the participation of various cell surface molecules and the efficacy of various cell types in the deletion of Ag-specific immature thymocytes. Thymocytes from mice expressing a transgenic TCR specific for the male Ag presented by the H-2Db class I MHC molecule were used as a target for deletion. In H-2d transgenic mice, cells bearing the transgenic TCR are not subjected to thymic selection as a consequence of the absence of the restricting H-2Db molecule but, nevertheless, express this TCR on the vast majority of immature CD4+8+ thymocytes. In this report we show that CD4+8+ thymocytes from H-2d TCR-transgenic mice are preferentially killed upon in vitro culture with male APC; DC were particularly effective in mediating in vitro deletion when compared with either B cells or T cells. Deletion of CD4+8+ thymocytes by DC was H-2b restricted and could be inhibited by mAb to either LFA-1 alpha or CD8. Partial inhibition was observed with mAb to ICAM-1, whereas mAb to CD4 and LFA-1 beta were without effect. These results are the first direct evidence of LFA-1 involvement in negative selection and provide further direct support for the participation of CD8/class I MHC interactions in this process. Like the requirements for deletion, activation of mature male-specific CD4-8+ T cells from female H-2b TCR-transgenic mice was also largely dependent on Ag presentation by DC and required both LFA-1/ICAM and CD8/class I MHC interactions; these results support the view that activation and deletion may represent maturation stage-dependent consequences of T cells encountering the same APC. Finally, our results also support the hypothesis that negative selection (deletion) does not require previous positive selection because deletion was observed under conditions where positive selection had not occurred.

Animals↗

Regulation of the expression of ICAM-1 on human monocytes and monocytic tumor cell lines.

In this study we investigated the mechanisms regulating expression of ICAM-1 that plays an important role for Ag presentation, on peripheral blood monocytes, and three myelomonocytic cell lines representing different stages of monocyte maturation. ICAM-1 expression on freshly isolated monocytes was low in all donors tested. After 16- to 20-h incubation, about a 20-fold increase was observed, whereas ICAM-1 expression on lymphocytes did not change. This marked increase in Ag expression was specific for ICAM-1, because expression of other monocyte Ag remained unchanged (alpha-chain of lymphocyte function-associated Ag-1) or decreased (ICAM-2, alpha-chains of CR3 and CR4, their common beta-chain and Fc gamma RI) during overnight incubation; only HLA-DR showed a slight increase. Enhanced expression of ICAM-1 was not caused by adherence; it was also not due to trace amounts of IFN-gamma possibly present under our culture conditions. Endotoxin contamination of the medium was excluded as a cause for the enhanced expression, and neither LPS nor its antagonist polymyxin B were able to alter ICAM-1 expression. Whole blood culture almost completely prevented up-regulation of ICAM-1 expression, thus apparently mimicking the in vivo situation. Culture of monocytes together with other PBMC had no significant influence on monocyte ICAM-1 levels. From 12 different cytokines tested for their ability to modulate "spontaneous" up-regulation of ICAM-1 in culture, only IFN-gamma was found to increase expression about twofold. This effect was also observed in whole blood culture. All other cytokines had no significant effect. In contrast, ICAM-1 expression on two of the three cell lines (KG1 and HL60) was inducible by TNF-alpha to a much higher degree than by IFN-gamma, whereas the results with U937 were comparable with those obtained for normal monocytes. The protein- and RNA-synthesis inhibitors cycloheximide and actinomycin D prevented expression of ICAM-1 in a dose-dependent fashion. In Northern blot experiments no difference in the amounts of mRNA was observed between freshly isolated and cultured monocytes, indicating that "spontaneous" induction of ICAM-1 is regulated at a posttranscriptional level. In contrast, stimulation with IFN-gamma caused a significant increase of detectable RNA comparable to that observed for Ag expression. These results disclose a very special regulation of ICAM-1 expression on monocytes which could be consistent with the view that ICAM-1 is actively down-regulated in vivo until the monocyte leaves the circulation.

Antigens, CD↗

Stimulation of human naive and memory T helper cells with bacterial superantigen. Naive CD4+45RA+ T cells require a costimulatory signal mediated through the LFA-1/ICAM-1 pathway.

The role of the accessory molecule ICAM-1 in activation of subpopulations of human T cells was examined using the bacterial superantigen staphylococcal enterotoxin A (SEA) as a MHC class II and TCR-dependent polyclonal T cell activator. Human T cells responded with different sensitivity to SEA when presented on mouse accessory cells expressing a human transfected MHC class II gene product. Mouse L cells cotransfected with both MHC class II (DR2A or DR7) and ICAM-1-stimulated T cells at 100-fold lower concentrations of SEA as compared to the single transfected cells. mAb reacting with the CD11a, CD18, or ICAM-1 molecules efficiently inhibited T cell activation with the cotransfected HLA-DR2A/ICAM-1 cell but did not influence T cell activation with the HLA-DR2A single transfected cell. Analysis of the ICAM-1 requirement on CD4+ memory (CD4+45RO+) and naive (CD4+45RA+) T cells revealed that CD4+45RA+ naive Th cells were hyporesponsive to SEA-induced activation with the HLA-DR2A single transfectant. However, cotransfection of ICAM-1 enabled these cells to respond to low doses of SEA implicating that they are more dependent on accessory molecules than the CD4+45RO+ cells. rICAM-1 immobilized on a plastic surface, was able to strongly costimulate SEA-induced T cell activation with the HLA-DR2A single transfectant, suggesting that costimulatory signals mediated to the T cells through LFA-1 can be delivered physically separated from the TCR signal. CD4+45RO+ memory and CD4+45RA+ naive Th cells apparently differ in their capacities to be activated by SEA bound to HLA-DR. Although the TCR molecule densities are similar in these two subsets, costimulation with ICAM-1 is required for activation of the CD4+45RA+, but not the CD4+45RO+ T cell subset at 1 to 10,000 ng/ml concentrations of SEA. This observation indicates different activation thresholds of naive and memory Th cells when triggering the TCR over a wide dose interval of superantigen.

Antigens, Bacterial↗

Immunologic reactions in amyotrophic lateral sclerosis brain and spinal cord tissue.

Expression of proteins associated with immune function was investigated immunohistochemically in postmortem brain and spinal cord of patients with amyotrophic lateral sclerosis (ALS). Reactive microglia/macrophages displaying high levels of leukocyte common antigen (LCA), the immunoglobulin receptor Fc gamma R1, lymphocyte function associated molecule-1 (LFA-1), the complement receptors CR3 and CR4, the class II major histocompatibility complex molecules HLA-DR, HLA-DP and HLA-DQ and common determinants of the class I HLA-A,B,C complex were abundant in affected areas in ALS. These areas included the primary motor cortex, motor nuclei of the brain stem, the anterior horn of the spinal cord, and the full extent of the corticospinal tract. A significant number of T lymphocytes of the helper/inducer (CD4+) and cytotoxic/suppressor (CD8+) subtypes were observed marginating along the walls of capillaries and venules and extending into the parenchyma of affected areas. Clusters of complement activated oligodendroglia as well as degenerating neurites positive for C3d and C4d were frequently detected in ALS-affected areas. These data provide evidence of immune-effector changes in ALS. They are consistent with an autoimmune or slow virus theory of the disorder, but may reflect only secondary changes.

Amyotrophic Lateral Sclerosis↗

Cetirizine does not influence the immune response.

Antihistamines are frequently employed in the treatment of allergic rhinitis and urticaria-angioedema syndrome. We analyzed the in vitro effects of cetirizine on the immune response. To this end the proliferation of peripheral mononuclear cells induced by mitogen and by -CD3, -CD2, or -CD28 monoclonal antibodies has been studied. Since the plasma peak of cetirizine following ingestion of 10 mg is about 1 microgram/mL, the drug was tested in the cultures at the concentration of 0.1, 1, or 10 micrograms/mL. No influence of cetirizine on T cell proliferation was detected. We also evaluated the effect of cetirizine on the expression of the following markers expressed by T cells upon activation: lymphocyte markers ICAM-1, HLA-DR, and CD25 surface expression, alpha-1-acid glycoprotein has been also studied. There was no effect of cetirizine on the investigated immunologic parameters; these data acquire clinical relevance when related to previous reports showing a depression of the immunologic response exerted by other compounds such as ketotifen and theophylline and when related to the recent data about the modulation of ICAM-1 expression on eosinophils by cetirizine. Cetirizine does not affect ICAM-1 expression of lymphocyte membrane.

Adult↗

Various cell types in human atherosclerotic lesions express ICAM-1. Further immunocytochemical and immunochemical studies employing monoclonal antibody 10F3.

The specificity of monoclonal antibody 10F3, generated to smooth muscle cells isolated from fetal human aorta, has been further explored in a series of biological, biochemical, and immunocytochemical studies. In the first assay, it was found that 10F3 could inhibit aggregation of phytohemagglutinin (PHA)-induced lymphocytes in a manner comparable to that of antibody RR1/1, an anti-intercellular adhesion molecule 1 (ICAM-1) monoclonal antibody. In immunoprecipitation experiments followed by one-dimensional gel electrophoresis, both 10F3 and RR1/1 immunoprecipitated 90 kd proteins, with results suggesting that the two antibodies recognized different epitopes of the same molecule. A series of immunocytochemical studies on human atherosclerotic lesions was performed; using single-labeling techniques, 10F3-positive cells were found in the vessel wall and in lesions of virtually all specimens of fatty streaks and fibrous plaques. Using double-labeling techniques, 10F3-positive macrophages and 10F3-positive smooth muscle cells were found; however, there were also a significant number of non-smooth muscle, nonmacrophage 10F3-positive cells. These studies demonstrate that 10F3 identifies ICAM-1, and that this protein is expressed on a variety of cell types in human atherosclerotic lesions. ICAM-1 may represent a developmentally regulated protein that is expressed in fetal but not adult mesenchymal cells, but can be re-expressed in pathologic processes such as atherosclerosis.

Adult↗

The differential reactivity of cells of the melanocytic lineage with four monoclonal antibodies against IFN-gamma inducible molecules.

The reactivity of four monoclonal antibodies (MAbs) directed against IFN-gamma inducible antigens with melanocytic cells was investigated in the course of local and systemic tumor progression of human malignant melanoma. Frozen sections of histologically defined melanocytic tissues at different stages of progression were stained with these MAbs using an indirect immunoperoxidase technique. The reactivity of MAbs Me15/B3 and Me15/F9, directed against two different epitopes of a 90-kDa molecule, was found to correlate with melanoma progression. Indeed, a significantly lower percentage of small than of advanced primary melanomas or metastases stained positively. A differential staining of nevocytic and dysplastic nevi was further observed for these two MAbs, which were also non-reactive with normal skin melanocytes. The reactivity of MAb Me14/D12, which identifies the intercellular adhesion molecule ICAM-1 and MAb Mel14/F12, directed against a 40-kDa molecule, was found to be independent of the Breslow thickness of primary melanomas. Both the latter MAbs stained a high proportion of nevocytic and dysplastic nevi. The co-expression of the surface molecules defined by MAbs Me14/D12, Me15/B3 and Me15/F9 in the course of melanoma progression was also analyzed. The frequency of this co-expression increased according to the Breslow thickness of primary melanomas. In addition, up to 100% of metastases, as opposed to 20% of dysplastic nevi, were found to be simultaneously stained by these three MAbs. It is therefore conceivable that high-risk melanocytic lesions might be identified by the use of a combination of MAbs directed against IFN-gamma regulated antigens.

Antibodies, Monoclonal↗