Binding of human rhinovirus and T cells to intercellular adhesion molecule-1 on human fibroblasts. Discordance between effects of IL-1 and IFN-gamma.

Intercellular adhesion molecule-1 (ICAM-1) is found on the surface of many hemopoietic and non-hemopoietic cells and can function as an adhesive ligand for the integrin, leukocyte function associated molecule-1 (LFA-1, CD11a/CD18). ICAM-1/LFA-1 interaction is thought to be of importance in many immune mediated cell-cell adhesion reactions. Recently, the major human rhinovirus (HRV) receptor has been identified as ICAM-1. HRV has been shown to bind specifically to ICAM-1 on transfected COS cells and to purified ICAM-1, which has been adsorbed to plastic microtiter wells. We have compared the ability of ICAM-1 expressed on the surface of human fibroblasts (FB) to function as a receptor for HRV as well as a receptor for LFA-1-bearing human T lymphocytes. We show that FB stimulation by the cytokines IFN-gamma or IL-1, both known inducers of ICAM-1 synthesis and expression in FB, induced an increase in HRV binding to treated cells, which could be inhibited by antibody to ICAM-1. In contrast, only IFN-gamma and not IL-1 treatment of FB resulted in an increased adhesion of T lymphocytes. Binding of HRV to IFN-gamma-treated FB inhibited the subsequent adhesion of T cells. We also show that prior stimulation of FB with IL-1 enhanced the adhesion of HRV to IFN-gamma-stimulated cells, although IL-1 pretreatment was inhibitory for T cell adhesion. As these two cytokines both up-regulate ICAM-1 on the surface of human FB, the contrasting effects of IFN-gamma and IL-1 on human FB ICAM-1 adhesion to HRV and to LFA-1 suggest that qualitative as well as quantitative alterations of the ICAM-1 molecule may contribute to its specificity of ligand recognition.     

A human intercellular adhesion molecule (ICAM-1) distinct from LFA-1

Homotypic adhesion by phorbol ester-stimulated lymphocytes requires LFA-1 and Mg+2 and does not involve like-like interactions between LFA-1 molecules on adjacent cells. The latter finding suggested that a second molecule, distinct from LFA-1, also participates in LFA-1-dependent adhesion. The identification of such a molecule was the object of this investigation. After immunization with LFA-1-deficient EBV-transformed lymphoblastoid cells, a MAb was obtained that inhibits phorbol ester-stimulated aggregation of LFA-1+ EBV lines. This MAb defines a novel cell surface molecule, which is designated intercellular adhesion molecule 1 (ICAM-1). ICAM-1 is distinct from LFA-1 in both cell distribution and structure. In SDS-PAGE, ICAM-1 isolated from JY cells is a single chain of Mr = 90,000. As shown by MAb inhibition, ICAM-1 participates in phorbol ester-stimulated adhesion reactions of B lymphocyte and myeloid cell lines and T lymphocyte blasts. However, aggregation of one T lymphocyte cell line (SKW-3) was inhibited by LFA-1 but not ICAM-1 MAb. It is proposed that ICAM-1 may be a ligand in many, but not all, LFA-1-dependent adhesion reactions.     

Functional involvement of the LFA-1/ICAM-1 adhesion system in the autologous mixed lymphocyte reaction

The integrin surface molecule termed lymphocyte functional antigen-1 (LFA-1), and its physiological ligand intercellular adhesion molecule-1 (ICAM-1), have been proven to play a relevant role in several immune reactions where cell-to-cell contact is required: these reactions include allogeneic mixed lymphocyte reaction (MLR) and direct cytotoxicity. In the present study, we show that monoclonal antibodies (mAbs) directed to LFA-1 as well as to ICAM-1 molecules are able to inhibit T cell proliferation in autologous MLR (AMLR). Such an in vitro reaction is generally considered a functional model of Ia-mediated immunocompetent cell cooperation, and is impaired in several pathological conditions. It is noteworthy that the LFA-1 molecule is largely represented on the T cell surface, whereas ICAM-1 is poorly expressed on resting T cells: autologous stimulation slightly increases ICAM-1 expression. Pretreatment studies indicate that the inhibitory effect of anti-ICAM-1 mAb on T cell proliferation in AMLR is exerted on responder T cells.     

Induction by IL 1 and interferon-gamma: tissue distribution, biochemistry, and function of a natural adherence molecule (ICAM-1)

ICAM-1 is a cell surface glycoprotein originally defined by a monoclonal antibody (MAb) that inhibits phorbol ester-stimulated leukocyte aggregation. Staining of frozen sections and immunofluorescence flow cytometry showed intercellular adhesion molecule-1 (ICAM-1) is expressed on non-hematopoietic cells such as vascular endothelial cells, thymic epithelial cells, certain other epithelial cells, and fibroblasts, and on hematopoietic cells such as tissue macrophages, mitogen-stimulated T lymphocyte blasts, and germinal center dendritic cells in tonsils, lymph nodes, and Peyer's patches. ICAM-1 staining on vascular endothelial cells is most intense in T cell areas in lymph nodes and tonsils showing reactive hyperplasia. ICAM-1 is expressed in low amounts on peripheral blood leukocytes. Phorbol ester-stimulated differentiation of myelomonocytic cell lines greatly increases ICAM-1 expression. ICAM-1 expression on dermal fibroblasts is increased threefold to fivefold by either interleukin 1 (IL 1) or interferon-gamma at 10 U/ml over a period of 4 or 10 hr, respectively. The induction is dependent on protein and mRNA synthesis and is reversible. ICAM-1 displays Mr heterogeneity in different cell types with a Mr of 97,000 on fibroblasts, 114,000 on the myelomonocytic cell line U937, and 90,000 on the B lymphoblastoid cell JY. ICAM-1 biosynthesis involves a Mr approximately 73,000 intracellular precursor. The non-N-glycosylated form resulting from tunicamycin treatment has a Mr of 55,000. ICAM-1 isolated from phorbol myristic acetate (PMA) stimulated U937 and from fibroblasts yields an identical major product of Mr = 60,000 after chemical deglycosylation. ICAM-1 MAb interferes with the adhesion of phytohemagglutinin blasts, and the adhesion of the cell line SKW3 to human dermal fibroblast cell layers. Pretreatment of fibroblasts but not lymphocytes with ICAM-1 MAb, and of lymphocytes but not fibroblasts with lymphocyte function-associated antigen 1 MAb inhibits adhesion. Intercellular adhesion is increased by prior exposure of fibroblasts to IL 1, and correlates with induction of ICAM-1.     

Lymphocyte function-associated antigen-1 (LFA-1) interaction with intercellular adhesion molecule-1 (ICAM-1) is one of at least three mechanisms for lymphocyte adhesion to cultured endothelial cells

Intercellular adhesion molecule-1 (ICAM-1) on the surface of cultured umbilical vein and saphenous vein endothelial cells was upregulated between 2.5- and 40-fold by rIL-1, rTNF, LPS and rIFN gamma corresponding to up to 5 X 10(6) sites/cell. Endothelial cell ICAM-1 was a single band of 90 kD in SDS-PAGE. Purified endothelial cell ICAM-1 reconstituted into liposomes and bound to plastic was an excellent substrate for both JY B lymphoblastoid cell and T lymphoblast adhesion. Adhesion to endothelial cell ICAM-1 in planar membranes was blocked completely by monoclonal antibodies to lymphocyte function associated antigen-1 (LFA-1) or ICAM-1. Adhesion to artificial membranes was most sensitive to ICAM-1 density within the physiological range found on resting and stimulated endothelial cells. Adhesion of JY B lymphoblastoid cells, normal and genetically LFA-1 deficient T lymphoblasts and resting peripheral blood lymphocytes to endothelial cell monolayers was also assayed. In summary, LFA-1 dependent (60-90% of total adhesion) and LFA-1-independent basal adhesion was observed and the use of both adhesion pathways by different interacting cell pairs was increased by monokine or lipopolysaccharide stimulation of endothelial cells. The LFA-1-dependent adhesion could be further subdivided into an LFA-1/ICAM-1-dependent component which was increased by cytokines and a basal LFA-1-dependent, ICAM-1-independent component which did not appear to be affected by cytokines. We conclude that ICAM-1 is a regulated ligand for lymphocyte-endothelial cell adhesion, but at least two other major adhesion pathways exist.     

IL-4 regulates endothelial cell activation by IL-1, tumor necrosis factor, or IFN-gamma.

Alteration in the surface membrane of endothelial cells (EC) is a feature of endothelial activation both at sites of inflammation in vivo and after stimulation with cytokines in vitro. The effects of stimulating EC with IL-1 or TNF include enhanced adhesiveness for polymorphonuclear leukocytes (PMN) and T cells, the induction of EC leukocyte adhesion molecule-1 (ELAM-1) expression, and the increased expression of intercellular adhesion molecule-1 (ICAM-1) and the 1.4C3 Ag. In contrast, IFN-gamma stimulation increases EC binding of T cells but not PMN and enhances ICAM-1 expression but not ELAM-1 or 1.4C3 Ag expression. Recently we have reported that the T cell-derived cytokine IL-4 also increases EC adhesiveness for T cells but not PMN. In this study we have examined the effect of IL-4 on the expression of several cytokine-inducible EC activation Ag, by using a previously described ELISA technique. IL-4 modulation of activation Ag expression was concentration dependent, optimal at around 100 U/ml, and exhibited a unique pattern compared to that seen with the other cytokines. Although, IL-4 stimulation increased 1.4C3 Ag expression (p less than 0.001), it significantly inhibited constitutive ICAM-1 expression (p less than 0.01) and did not induce ELAM-1. Furthermore, IL-4 exhibited significant synergy with IL-1 or TNF in inducing 1.4C3 Ag expression (p less than 0.001) but inhibited the increased expression of ICAM-1 produced by IL-1, TNF, or IFN-gamma (p less than 0.01) and inhibited the induction of ELAM-1 by IL-1 and TNF (p less than 0.001). In contrast, IL-4 had no effect on the expression of EC HLA-class I, -DR, -DP, or -DQ and neither enhanced nor inhibited the effect of IFN-gamma on the expression of these molecules. Finally, although IL-4 alone caused little if any shape change in EC monolayers, it strongly synergized with TNF or IFN-gamma in causing a change in shape to a more fibroblastic morphology. These observations indicate that IL-4 increases EC adhesiveness for T cells by the induction of a different adhesion molecule to ICAM-1. Furthermore, the ability of IL-4 to both enhance and inhibit the expression of activation Ag on EC already activated by IL-1, TNF, or IFN-gamma suggests that it may be important in altering the quality of inflammatory responses such as may occur during the development and maintenance of chronic or immune-mediated inflammation.     

Intrinsic ICAM-1/LFA-1 activation mediates altered responsiveness of atopic asthmatic airway smooth muscle

Cell adhesion molecules (CAMs) have been importantly implicated in the pathobiology of the airway responses in allergic asthma, including inflammatory cell recruitment into the lungs and altered bronchial responsiveness. To elucidate the mechanism of CAM-related mediation of altered airway responsiveness in the atopic asthmatic state, the expressions and actions of intercellular adhesion molecule-1 (ICAM-1) and its counterreceptor ligand lymphocyte function-associated antigen-1 (LFA-1; i.e., CD11a/CD18) were examined in isolated rabbit airway smooth muscle (ASM) tissues and cultured human ASM cells passively sensitized with sera from atopic asthmatic patients or nonatopic nonasthmatic (control) subjects. Relative to control tissues, the atopic asthmatic sensitized ASM exhibited significantly enhanced maximal contractility to acetylcholine and attenuated relaxation responses to isoproterenol. These proasthmatic changes in agonist responsiveness were ablated by pretreating the atopic sensitized tissues with a monoclonal blocking antibody (MAb) to either ICAM-1 or CD11a, whereas a MAb directed against the related beta(2)-integrin Mac-1 had no effect. Moreover, relative to control tissues, atopic asthmatic sensitized ASM cells displayed an autologously upregulated mRNA and cell surface expression of ICAM-1, whereas constitutive expression of CD11a was unaltered. Extended studies further demonstrated that 1) the enhanced expression and release of soluble ICAM-1 by atopic sensitized ASM cells was prevented when cells were pretreated with an interleukin (IL)-5-receptor-alpha blocking antibody and 2) administration of exogenous IL-5 to naive (nonsensitized) ASM cells induced a pronounced soluble ICAM-1 release from the cells. Collectively, these observations provide new evidence demonstrating that activation of the CAM counterreceptor ligands ICAM-1 and LFA-1, both of which are endogenously expressed in ASM cells, elicits autologously upregulated IL-5 release and associated changes in ICAM-1 expression and agonist responsiveness in atopic asthmatic sensitized ASM.     

Purified intercellular adhesion molecule-1 (ICAM-1) is a ligand for lymphocyte function-associated antigen 1 (LFA-1)

Lymphocyte function-associated antigen 1 (LFA-1) is a leukocyte cell surface glycoprotein that promotes intercellular adhesion in immunological and inflammatory reactions. It is an alpha beta complex that is structurally related to receptors for extracellular matrix components, and thus belongs to the integrin family. ICAM-1 (intercellular adhesion molecule-1) is a distinct cell surface glycoprotein. Its broad distribution, regulated expression in inflammation, and involvement in LFA-1-dependent cell-cell adhesion have suggested that ICAM-1 may be a ligand for LFA-1. We have purified ICAM-1 and incorporated it into artificial supported lipid membranes. LFA-1+ but not LFA-1- cells bound to ICAM-1 in the artificial membranes, and the binding could be specifically inhibited by anti-ICAM-1 treatment of the membranes or by anti-LFA-1 treatment of the cells. The cell binding to ICAM-1 required metabolic energy production, an intact cytoskeleton, and the presence of Mg2+ and was temperature dependent, characteristics of LFA-1- and ICAM-1-dependent cell-cell adhesion.     

Effect of cytokines on ICAM-1 and ZO-1 expression on human airway epithelial cells

The presence of adhesion molecules on airway epithelial cells may be important in recruiting leukocytes to the epithelium. The study aimed at investigating the effects of interleukin (IL)-4, IL-8, IL-13 and interferon-gamma (IFN-gamma) on cell viability and intracellular adhesion molecule (ICAM)-1 and zonula occludens protein (ZO)-1 expression on cultured human basal and columnar airway epithelial cells. Cycloheximide (CHX) induced cell death in both cell lines. The cytokines IL-4, IL-8, IL-13 and IFN-gamma had only minor effects on cell proliferation in the columnar 16HBE14o-cells, and inhibited the effects of CHX on cell death. IFN-gamma increased ICAM-1 expression in both cell lines. Western blot analysis showed that CHX inhibited both ICAM-1 and ZO-1 expression in the basal cell line. A combination of IL-4 and IFN-gamma appeared to break the tight junctions. IL-4 and IL-13 potentiated CHX-induced apoptosis in basal cells but not in columnar cells, possibly due to low levels of the IL-4 receptor. It is concluded that cytokines produced by airway epithelium may have a role in regulating sequestering of leukocytes to the airways during airway inflammation.     

ICAM-3 interacts with LFA-1 and regulates the LFA-1/ICAM-1 cell adhesion pathway

The interaction of lymphocyte function-associated antigen-1 (LFA-1) with its ligands mediates multiple cell adhesion processes of capital importance during immune responses. We have obtained three anti-ICAM-3 mAbs which recognize two different epitopes (A and B) on the intercellular adhesion molecule-3 (ICAM-3) as demonstrated by sequential immunoprecipitation and cross-competitive mAb-binding experiments. Immunoaffinity purified ICAM-3-coated surfaces were able to support T lymphoblast attachment upon cell stimulation with both phorbol esters and cross-linked CD3, as well as by mAb engagement of the LFA-1 molecule with the activating anti-LFA-1 NKI-L16 mAb. T cell adhesion to purified ICAM-3 was completely inhibited by cell pretreatment with mAbs to the LFA-1 alpha (CD11a) or the LFA-beta (CD18) integrin chains. Anti-ICAM-3 mAbs specific for epitope A, but not those specific for epitope B, were able to trigger T lymphoblast homotypic aggregation. ICAM-3-mediated cell aggregation was dependent on the LFA-1/ICAM-1 pathway as demonstrated by blocking experiments with mAbs specific for the LFA-1 and ICAM-1 molecules. Furthermore, immunofluorescence studies on ICAM-3-induced cell aggregates revealed that both LFA-1 and ICAM-1 were mainly located at intercellular boundaries. ICAM-3 was located at cellular uropods, which in small aggregates appeared to be implicated in cell-cell contacts, whereas in large aggregates it appeared to be excluded from cell-cell contact areas. Experiments of T cell adhesion to a chimeric ICAM-1-Fc molecule revealed that the proaggregatory anti-ICAM-3 HP2/19 mAb was able to increase T lymphoblast attachment to ICAM-1, suggesting that T cell aggregation induced by this mAb could be mediated by increasing the avidity of LFA-1 for ICAM-1. Moreover, the HP2/19 mAb was costimulatory with anti-CD3 mAb for T lymphocyte proliferation, indicating that enhancement of T cell activation could be involved in ICAM-3-mediated adhesive phenomena. Altogether, our results indicate that ICAM-3 has a regulatory role on the LFA-1/ICAM-1 pathway of intercellular adhesion.     

Molecular cloning of murine intercellular adhesion molecule (ICAM-1).

We have previously reported a murine lymphocyte surface antigen MALA-2 of approximately 95,000 Mr which is expressed mainly on activated lymphocytes. The rat monoclonal antibody YN1/1 that detects this antigen profoundly inhibits mixed lymphocyte response. We have now purified MALA-2 and determined its partial amino acid sequence. By using non-redundant synthetic oligonucleotides as probes, based on the amino acid sequence, we have isolated two full length cDNA clones encoding MALA-2. The two clones are identical except for the 5' end sequence. Expression of MALA-2 on transfected COS cells is only achieved with one of the two cDNA clones. The nucleotide sequence as well as the deduced amino acid sequence of MALA-2 display striking homology with those of the recently reported human intercellular adhesion molecule ICAM-1. All the unique features of the human ICAM-1, including its homology with the neural adhesion molecule NCAM, its internal repeat structure and the immunoglobulin-like structure, are found in MALA-2. Furthermore, purified MALA-2 crosslinked to a solid support binds Con A blasts that express LFA-1, the putative receptor for ICAM-1, and the binding can be blocked by YN1/1 antibody or antimurine LFA-1 antibody indicating a direct interaction of these molecules in cell adhesion. Therefore, we consider MALA-2 to be the murine homolog of human ICAM-1. Since ICAM-1 is known to be of primary importance in immune responses and inflammatory reactions, having a monoclonal antibody and a mouse model will provide the opportunity to study the functional role of ICAM-1 in vivo.     

Functional evaluation of DC-SIGN monoclonal antibodies reveals DC-SIGN interactions with ICAM-3 do not promote human immunodeficiency virus type 1 transmission

DC-SIGN, a type II membrane-spanning C-type lectin that is expressed on the surface of dendritic cells (DC), captures and promotes human and simian immunodeficiency virus (HIV and SIV) infection of CD4(+) T cells in trans. To better understand the mechanism of DC-SIGN-mediated virus transmission, we generated and functionally evaluated a panel of seven monoclonal antibodies (MAbs) against DC-SIGN family molecules. Six of the MAbs reacted with myeloid-lineage DC, whereas one MAb preferentially bound DC-SIGNR/L-SIGN, a homolog of DC-SIGN. Characterization of hematopoietic cells also revealed that stimulation of monocytes with interleukin-4 (IL-4) or IL-13 was sufficient to induce expression of DC-SIGN. All DC-SIGN-reactive MAbs competed with intercellular adhesion molecule 3 (ICAM-3) for adhesion to DC-SIGN and blocked HIV-1 transmission to T cells that was mediated by THP-1 cells expressing DC-SIGN. Similar but less efficient MAb blocking of DC-mediated HIV-1 transmission was observed, indicating that HIV-1 transmission to target cells via DC may not be dependent solely on DC-SIGN. Attempts to neutralize DC-SIGN capture and transmission of HIV-1 with soluble ICAM-3 prophylaxis were limited in success, with a maximal inhibition of 60%. In addition, disrupting DC-SIGN/ICAM-3 interactions between cells with MAbs did not impair DC-SIGN-mediated HIV-1 transmission. Finally, forced expression of ICAM-3 on target cells did not increase their susceptibility to HIV-1 transmission mediated by DC-SIGN. While these findings do not discount the role of intercellular contact in facilitating HIV-1 transmission, our in vitro data indicate that DC-SIGN interactions with ICAM-3 do not promote DC-SIGN-mediated virus transmission.     

Stimulation of B lymphocytes through surface Ig receptors induces LFA-1 and ICAM-1-dependent adhesion.

Engagement of the surface Ig receptor with anti-IgM antibodies stimulates murine B lymphocytes to markedly increase their expression of the cell adhesion molecules ICAM-1 and LFA-1. Stimulated B cells display increased homotypic adhesiveness and form spontaneous heterotypic conjugates with T lymphocytes. This latter T-B cell interaction is further enhanced if T cells have been previously activated with phorbol esters. In all cases, the formation of cell-cell conjugates is dependent on LFA-1-ICAM-1-mediated interactions as assessed in mAb blocking experiments. B lymphocytes stimulated with anti-IgM display a marked increase in binding to ICAM-1-transfected L cells. This cell-cell interaction is inhibited by anti-LFA-1 mAb binding to the B lymphocyte. Together, these results demonstrate that there is an induction of both ICAM-1 and LFA-1 on stimulated B cells and a corresponding increase in the adhesiveness of these cells. These findings suggest that Ag binding to the surface Ig receptor could prepare a B lymphocyte for subsequent interaction with a T lymphocyte. This provides insight into how efficient T-B collaboration may occur between very infrequent Ag-specific lymphocytes.     

Rolling of Th1 cells via P-selectin glycoprotein ligand-1 stimulates LFA-1-mediated cell binding to ICAM-1

Activated T cells migrate from the blood into nonlymphoid tissues through a multistep process that involves cell rolling, arrest, and transmigration. P-Selectin glycoprotein ligand-1 (PSGL-1) is a major ligand for P-selectin expressed on subsets of activated T cells such as Th1 cells and mediates cell rolling on vascular endothelium. Rolling cells are arrested through a firm adhesion step mediated by integrins. Although chemokines presented on the endothelium trigger integrin activation, a second mechanism has been proposed where signaling via rolling receptors directly activates integrins. In this study, we show that Ab-mediated cross-linking of the PSGL-1 on Th1 cells enhances LFA-1-dependent cell binding to ICAM-1. PSGL-1 cross-linking did not enhance soluble ICAM-1 binding but induced clustering of LFA-1 on the cell surface, suggesting that an increase in LFA-1 avidity may account for the enhanced binding to ICAM-1. Combined stimulation by PSGL-1 cross-linking and the Th1-stimulating chemokine CXCL10 or CCL5 showed a more than additive effect on LFA-1-mediated Th1 cell adhesion as well as on LFA-1 redistribution on the cell surface. Moreover, PSGL-1-mediated rolling on P-selectin enhanced the Th1 cell accumulation on ICAM-1 under flow conditions. PSGL-1 cross-linking induced activation of protein kinase C isoforms, and the increased Th1 cell adhesion observed under flow and also static conditions was strongly inhibited by calphostin C, implicating protein kinase C in the intracellular signaling in PSGL-1-mediated LFA-1 activation. These results support the idea that PSGL-1-mediated rolling interactions induce intracellular signals leading to integrin activation, facilitating Th1 cell arrest and subsequent migration into target tissues.     

Cytokines modulate endothelial cell intracellular signal transduction required for VCAM-1-dependent lymphocyte transendothelial migration

Vascular cell adhesion molecule-1 (VCAM-1) activates endothelial cell NADPH oxidase which catalyzes production of reactive oxygen species (ROS). This activity is required for VCAM-1-dependent lymphocyte migration. The focus of our study was to determine whether these VCAM-1-dependent functions are modulated by cytokines. TGF-beta1 or IFN-gamma pretreatment of mouse endothelial cell lines inhibited VCAM-1-dependent B and T cell transendothelial migration without affecting initial lymphocyte adhesion. Neutralizing anti-TGF-beta1 blocked the effects of TGF-beta1 pretreatment of endothelial cells, whereas addition of anti-TGF-beta1 after TGF-beta1 pretreatment of the endothelial cells did not block TGF-beta1-mediated inhibition. Neutralizing anti-IFN-gamma also blocked the inhibitory effects of IFN-gamma. TGF-beta1 and IFN-gamma blocked migration by inhibiting the VCAM-1-stimulated production of low levels of ROS (0.1-0.9 microM H2O2). These results demonstrate that both TGF-beta1 and IFN-gamma directly affect the endothelial cells' ability to promote lymphocyte migration. IL-4 had differing effects on T and B cells during transmigration. IL-4 augmented T cell migration across the endothelial cell lines but did not affect T cell adhesion. Conversely, IL-4 increased B cell adhesion to the endothelial cell lines without affecting migration. In summary, cytokines can directly modulate microvascular endothelial cell intracellular signaling, demonstrating a new level of cytokine regulation of lymphocyte diapedesis.