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Objectives: To study the role of cytokines on adhesion molecule expression and binding of activated T cells to synovial type B cells., Methods: Adhesion molecule expression was examined by immunofluorescence and adhesion of 51Cr-labelled T cells to the synovial cells determined., Results: Tumor necrosis factor alpha/interferon gamma (TNF alpha/IFN-gamma) and interleukin 1 alpha (IL-1 alpha)/IFN-gamma enhanced adhesion molecule expression and the adhesion of T cells to synovial cells. Anti-intercellular adhesion molecule 1 blocked adhesion of T cells to TNF alpha/IFN-gamma and IL-1 alpha/IFN-gamma stimulated synovial cells while an antibody to CD61 blocked adhesion to IL-1 alpha/IFN-gamma stimulated cells., Conclusions: The interaction of leukocytes with adhesion molecules on synovial cells may play a role in recruitment of these cells to an inflammatory site.

On the basis of reports demonstrating possible roles for leukocyte function-associated antigen 1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1), the ligand for LFA-1, in human immunodeficiency virus type 1 (HIV-1) infection, we have explored the involvement of the ICAM-1 molecule by using selected synthetic peptides derived from the protein sequence. Replication was assessed in MT-2 cells, highly susceptible to HIV infection, in the presence of four synthetic peptides derived from the ICAM-1 amino acid sequence. This cell type was chosen for the ability to form marked syncytia on infection with cell-free virus. Under the conditions used, minimal or no cytotoxicity was observed with the peptides up to concentrations of 50 micrograms/ml. A peptide corresponding to a unique region of ICAM-1, JF9 [ICAM-1(367-394, A-378)], had little effect on virus replication despite its ability to inhibit cell-cell adhesion. In contrast, an N-terminal peptide, JF7B [ICAM-1(1-23)], consistently inhibited virus replication in MT-2 cells in a dose-dependent manner, as measured by cell-free reverse transcriptase (RT) activity (up to 70% inhibition), soluble virus antigen production (up to 60% inhibition), and syncytium formation (virtually complete inhibition up to 6 days post infection). Testing of W-CAM-1 antibody, and anti-ICAM-1 antibody that inhibits cell-cell adhesion, revealed no significant inhibitory effects on RT activity, virus antigen production, and syncytium formation in HIV-1-infected MT-2 cells at a level that markedly inhibited cell-cell adhesion (10 micrograms/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

We report the expression on synovial cells of cell surface molecules known to be involved in T cell activation by antigen presenting cells. Normal human synovial fibroblasts and a human synovial cell line transformed with the SV40 large T antigen were used for in vitro stimulation studies with recombinant cytokines. We demonstrate an increase in MHC-A, B, C expression in normal synovial cells in response to recombinant interferon gamma (r gamma IFN), tumour necrosis factor alpha and beta (rTNF alpha and beta) and interleukin-1 (rIL-1 alpha). Intercellular adhesion molecular-1 (ICAM-1) expression was increased in parallel with MHC Class I. The combination of r gamma IFN and rTNF alpha was additive in its effect on ICAM-1 expression. Northern blot analysis suggests that ICAM-1 expression in synovial cells is controlled at the level of transcription. In contrast, MHC Class II (HLA-DR) was only significantly induced by r gamma IFN. Other stimuli including interleukin-4 (IL-4), interleukin 6 (IL-6), granulocyte macrophage colony stimulating factor (GM-CSF) and prostaglandin E2 (PGE2) did not affect the expression of ICAM-1 or MHC Class I and II. Leucocyte function antigen 3 (LFA-3) expression was not affected by any of the stimuli tested. Immunoperoxidase staining of rheumatoid synovial tissue confirmed enhanced in vivo expression of ICAM-1 in rheumatoid arthritis. These changes are discussed in the context of T cell activation in inflammatory arthritis.

Immunoperoxidase staining of samples of normal human retina and choroid was performed to demonstrate selected adhesion molecules in vivo. Intercellular adhesion molecule-1 (ICAM-1), lymphocyte function-associated antigen-3 (LFA-3) and endothelial leucocyte adhesion molecule-1 (ELAM-1) were expressed on retinal vascular endothelium and ICAM-1 and ELAM-1 in the region of the external limiting membrane. The very late antigen-2 (VLA-2) was found around the retinal ganglion cells and in the inner and outer fibre layers. The endothelium on the choriocapillaris showed moderate staining of ICAM-1, and slight staining of LFA-3 and ELAM-1. The presence of these molecules in this distribution strongly suggests they have an important role in the pathogenesis of immunologically mediated ocular conditions.

This study examines the expression of some selected adhesion molecules likely to be important in the migration of leucocytes across the blood-retinal and blood-aqueous barriers in samples of normal human retina and choroid by immunoperoxidase staining. ICAM-1, LFA-3 and ELAM-1 were expressed on retinal endothelium and ICAM-1, ELAM-1 and CD44 in the region of the external limiting membrane. VLA-2 was found around the retinal ganglion cells and in the inner and outer fibre layers and is likely to be important in maintaining the structural integrity of the retina. The endothelium on the choriocapillaris showed moderate staining of ICAM-1, and slight staining of LFA-3 and ELAM-1. These molecules may have an important functional role in the pathogenesis of many immunological ocular conditions, including uveoretinitis and corneal allograft rejection.

To explore the role of adhesion molecules in mediating mononuclear cell localisation, development of the granulomatous reaction, and cell mediated damage to the arterial wall in giant cell arteritis, 17 temporal artery biopsy specimens were examined. Eleven showed the histological features of giant cell arteritis and six showed no evidence of arteritis. All were examined for the expression of LFA-3, ICAM-1 and its receptor LFA-1, and HLA-DR. Temporal arteries with early features of arteritis, as well as histologically unaffected skip areas, showed a regional induction of ICAM-1 expression, but not HLA-DR, on smooth muscle cells of the media. ICAM-1 expression was detected in areas where a clinically important mononuclear cell infiltrate had not yet developed. In more florid cases of giant cell arteritis there was an additional widespread induction of ICAM-1 expression on intimal myofibroblasts. Strong expression of ICAM-1, HLA-DR, and LFA-3 was found on macrophages, epithelioid cells, and giant cells comprising the granulomatous lesion. The pattern of expression of these adhesion molecules suggests that they have a role in leucocyte traffic into the vascular lesion as well as in mediating the intercellular interactions which constitute the granulomatous response.

We have used a combination of hydropathy analysis of the intercellular adhesion molecule 1 (ICAM-1) sequence and dot-matrix comparison of the sequence with the homologous, but functionally distinct, protein myelin-associated glycoprotein to identify a putative functional binding region. One polar, and presumably surface-exposed, region of ICAM-1 showed no significant identity with myelin-associated glycoprotein. A synthetic peptide analog based on the sequence of this region (JF9) mimicked the inhibitory effects of the anti-ICAM-1 monoclonal antibody WEHI-CAM-1. These included inhibition of ICAM-1-dependent homotypic aggregation of Raji Burkitt lymphoma and phorbol-ester treated U937 cells at concentrations as low as 80 micrograms/ml (24 microM). In addition, at a concentration of 100 micrograms/ml, the peptide analog effectively inhibited cytotoxic cell activity, an ICAM-1-dependent effector function of the immune response. This simple method of sequence analysis may have general applicability to the identification of functional domains in homologous, but functionally distinct, proteins such as the translated products of gene families.

We have isolated and restriction enzyme-mapped a human genomic DNA clone encompassing the first two exons and the 5' flanking sequence of the human intercellular adhesion molecule-1 (ICAM-1) gene. The transcription initiation site was identified using primer extension analysis, and 1.7 kb of DNA upstream of the transcription initiation site was sequenced. The 5' region and first exon of the ICAM-1 gene was found to be a CpG island as it was (i) (G + C)-rich with a high frequency of the dinucleotide CpG and (ii) hypomethylated irrespective of the level of ICAM-1 expression in the tissues examined. These features of the ICAM-1 promoter are similar to the promoters of many 'housekeeping' genes. However, consensus sequences for several potential regulatory elements were found in the 5'-flanking sequence, an observation in keeping with the pattern of strongly regulated ICAM-1 expression. Examination of the chromatin structure upstream of the ICAM-1 gene revealed the presence of a constitutive DNase I-hypersensitive site 1.5 kb upstream of the transcription initiation site. Direct evidence that the upstream region constitutes a promoter element was demonstrated in transient transfection assays. A series of chloramphenicol acetyltransferase gene (CAT) constructs containing 5' fragments ranging in size from 1054 to 310 bp had equivalent levels of promoter activity when transfected into HeLa cells. Using a CAT construct containing a 447 bp ICAM-1 promoter fragment, we demonstrate an increase in transcription in response to interferon gamma (IFN-gamma), suggesting that this proximal region of the promoter is responsible, at least in part, for IFN-gamma induction of ICAM-1 expression.

High molecular weight DNA isolated from human tonsil was transfected into mouse L cells to produce transfectants expressing the human intercellular adhesion molecule [ICAM-1]. The transfected ICAM-1 molecule was highly expressed on the cell membrane and our studies show that the transfected ICAM-1 molecule was a fully functional adhesion protein. All leucocyte subtypes showed specific binding to the ICAM-1 transfectants, their adhesion being inhibited by Fab1 fragments of W-CAM-1 antibody and LFA-1 MoAb (leucocyte function antigen). B cell lines (RAJI, Nalm1) showed the highest degree of ICAM-1 mediated adhesion. Normal lymphoblasts showed comparable levels of binding whilst normal neutrophils (both resting and activated by (N-formyl-methionyl-leucyl-phenylalanine) fMLP) showed the least ICAM-1-mediated adhesion. Despite a significant level of adhesion to ICAM-1 transfectants shown by T lymphoblasts generated in a two way MLR there was no evidence of cytolysis of ICAM-1 transfectants. These studies demonstrate the potential of ICAM-1 transfectants as tools for analysis of the role of ICAM-1 in lymphoid adhesion.

SummaryThe contribution of synovial cells to the pathogenesis of rheumatoid arthritis (RA) is only partly understood. Monoclonal antibody (mAb) 1D5 is one of very few mAb ever raised against RA synovial cells in order to study the biology of these cells. Studies on the expression pattern and structural features of the 1D5 Ag suggest that 1D5 recognizes human vascular cell adhesion molecule-1 (VCAM-1), which is an intercellular adhesion molecule. Vascular cell adhesion molecule-1 may be involved in a number of crucial intercellular interactions in RA. [ABSTRACT FROM AUTHOR]