A human tumor necrosis factor (TNF) alpha mutant that binds exclusively to the p55 TNF receptor produces toxicity in the baboon

A number of recent studies have demonstrated that cellular responses to tumor necrosis factor (TNF) mediated by the p55 and the p75 TNF receptors are distinct. To evaluate the relative in vivo toxicities of wild-type TNF alpha (wtTNF alpha) and a novel p55 TNF selective receptor agonist, healthy, anesthetized baboons (Papio sp.) were infused with a near-lethal dose of either wtTNF alpha or a TNF alpha double mutant (dmTNF alpha) that binds specifically to the p55, but not to the p75, TNF receptor. Both wtTNF alpha and dmTNF alpha produced comparable acute hypotension, tachycardia, increased plasma lactate, and organ dysfunction in Papio. However, administration of wtTNF alpha produced a marked granulocytosis and loss of granulocyte TNF receptors, whereas little if any changes in neutrophil number or cell surface TNF receptor density were seen after dmTNF alpha mutant administration. Infusion of dmTNF alpha resulted in a plasma endogenous TNF alpha response that peaked after 90-120 min. We conclude that selective p55 TNF receptor activation is associated with early hemodynamic changes and the autocrine release of endogenous TNF alpha. Significant systemic toxicity results from p55 TNF receptor activation, but the role of the p75 TNF receptor in systemic TNF toxicity requires further study.     

Tumor necrosis factor (TNF)-soluble high-affinity receptor complex as a TNF antagonist

A novel high-affinity inhibitor of tumor necrosis factor (TNF) is described, which is created by the fusion of the extracellular domains of TNF-binding protein 1 (TBP-1) to both the alpha and beta chains of an inactive version of the heterodimeric protein hormone, human chorionic gonadotropin. The resulting molecule, termed TNF-soluble high-affinity receptor complex (SHARC), self-assembles into a heterodimeric protein containing two functional TBP-1 moieties. The TNF-SHARC is a potent inhibitor of TNF-alpha bioactivity in vitro and has a prolonged pharmacokinetic profile compared with monomeric TBP-1 in vivo. Consistent with the long half-life, the duration of action in an lipopolysaccharide-mediated proinflammatory mouse model is prolonged similarly. In a collagen-induced arthritis mouse model, this molecule demonstrates improved efficacy over monomeric TBP-1. Based on these results, we demonstrated that inactivated heterodimeric protein hormones are flexible and efficient scaffolds for the creation of soluble high-affinity receptor complexes.     

肿瘤坏死因子a促进人冠状动脉内皮细胞的凋亡

背景:研究表明冠状动脉内皮细胞凋亡参与了动脉粥样硬化的发生、发展过程。目的:观察肿瘤坏死因子a对人冠状动脉内皮细胞的诱导损伤作用。方法:取对数生长期的人冠状动脉内皮细胞c-12221,分别加入含0(对照),200,400,600mg/L肿瘤坏死因子a的培养液,采用MTT检测细胞增殖率变化,Hoechst 33258/PI双染观察凋亡细胞形态变化,Annexin V-FITC和PI双染流式检测细胞凋亡率变化,高内涵活细胞成像系统检测细胞线粒体膜电位变化。结果与结论:肿瘤坏死因子a呈剂量依赖性抑制人冠状动脉内皮细胞的增殖。Hoechst 33258/PI染色观察可见凋亡细胞染色质凝集、细胞核碎裂成碎片等典型细胞凋亡的特征性变化,不同质量浓度肿瘤坏死因子a组细胞凋亡率高于对照组(P<0.05),线粒体膜电位低于对照组(P<0.05),且呈剂量依赖性。表明肿瘤坏死因子a呈剂量依赖性促进人冠状动脉内皮细胞凋亡,抑制其增殖,作用机制与线粒体凋亡通路有关。     

Estradiol enhances leukocyte binding to tumor necrosis factor (TNF)-stimulated endothelial cells via an increase in TNF-induced adhesion molecules E-selectin, intercellular adhesion molecule type 1, and vascular cell adhesion molecule type 1.

Adhesion of leukocytes to endothelial cells is a critical step in the development of acute and chronic inflammatory lesions. We report here that estradiol treatment of cultured human umbilical vein endothelial cells stimulated up to a twofold increase in TNF-induced adhesion of both polymorphonuclear leukocytes and PMA-activated peripheral blood mononuclear cells. This effect was more evident (threefold increase) when endothelial cells were cultured on the basement membrane glycoprotein laminin. Progesterone, but not testosterone, had a similar stimulatory effect. Estradiol also promoted a slight increase in interferon gamma-stimulated endothelial cell adherence for peripheral blood mononuclear cells, but no effect of estradiol was observed when adhesion of leukocytes to endothelial cells was stimulated with IL-1 or IL-4. The estradiol-induced increase in leukocyte binding to human umbilical vein endothelial cells was partially blocked by antibodies to the adhesion molecules E-selectin, intercellular adhesion molecule type 1 (ICAM-1), and vascular cell adhesion molecule type 1 (VCAM-1). Indirect immunofluorescence techniques showed that estradiol produces an increase in TNF-induced cell surface expression of these molecules. Northern blot analysis demonstrated a transient increase in TNF-induced expression of mRNA for E-selectin, ICAM-1, and VCAM-1 in endothelial cells treated with estradiol. Our data demonstrate that estradiol has important regulatory functions in promoting leukocyte-endothelial cell interactions that might contribute to the observed predominance in females of some autoimmune inflammatory diseases.     

组织因子刺激体外培养人脐静脉内皮细胞肿瘤坏死因子α、白细胞介素1的表达

目的:组织因子介导了细胞凝集、组织损伤、血栓形成,从而参与"凝血-炎症-血栓形成"网络。组织因子是否为一种独立的前炎症介质介导炎症反应,刺激人脐静脉内皮细胞使之分泌肿瘤坏死因子α、白细胞介素1。方法:实验于2004-09/2006-02在贵阳医学院组织工程与干细胞实验中心(省级重点实验室)完成。利用重组的组织因子刺激体外培养的人脐静脉内皮细胞,并设立空白对照组、0.2mg/L组织因子刺激组和0.8mg/L组织因子刺激组,用ELISA检测不同组织因子刺激浓度在同一刺激时间(6h)其炎症介质(肿瘤坏死因子α、白细胞介素1)的表达分泌情况。结果:①组织因子可以刺激人脐静脉内皮细胞使之分泌肿瘤坏死因子α,0.2mg/L组织因子刺激组与0.8mg/L组织因子刺激组肿瘤坏死因子α水平高于空白对照组(P<0.05);0.8mg/L组织因子刺激组肿瘤坏死因子α水平高于0.2mg/L组织因子刺激组(P<0.05)。②与空白对照组相比较,0.2mg/L组织因子刺激组白细胞介素1水平未升高,0.8mg/L组织因子刺激组略有升高,但差异无显著性意义(P>0.05)。结论:组织因子可以作为一种前炎症介质介导炎症反应,使内皮细胞肿瘤坏死因子α表达增强。     

A Critical Role of the p75 Tumor Necrosis Factor Receptor (p75TNF-R) in Organ Inflammation Independent of ?TNF,Lymphotoxin α, or the p55TNF-R

Despite overwhelming evidence that enhanced production of the p75 tumor necrosis factor receptor (p75TNF-R) accompanies development of specific human inflammatory pathologies such as multi-organ failure during sepsis, inflammatory liver disease, pancreatitis, respiratory distress syndrome, or AIDS, the function of this receptor remains poorly defined in vivo. We show here that at levels relevant to human disease, production of the human p75TNF-R in transgenic mice results in a severe inflammatory syndrome involving mainly the pancreas, liver, kidney, and lung, and characterized by constitutively increased NF-κB activity in the peripheral blood mononuclear cell compartment. This process is shown to evolve independently of the presence of TNF, lymphotoxin α, or the p55TNF-R, although coexpression of a human TNF transgene accelerated pathology. These results establish an independent role for enhanced p75TNF-R production in the pathogenesis of inflammatory disease and implicate the direct involvement of this receptor in a wide range of human inflammatory pathologies.     

Stimulation of fibroblast chemotaxis by human recombinant tumor necrosis factor alpha (TNF-alpha) and a synthetic TNF-alpha 31-68 peptide

Macrophages are a major source of fibrogenic factors that promote healing of injured tissue. The recruitment of fibroblasts to sites of tissue injury is a prerequisite for optimal repair of tissue damage. In the present study, human recombinant tumor necrosis factor alpha (hrTNF-alpha), a major macrophage-derived cytokine, was demonstrated to be a potent fibroblast chemoattractant, inducing migration at picomolar concentrations. Anti-hrTNF-alpha monoclonal antibody neutralized most of the fibroblast chemotactic activity generated during short-term culture of human peripheral blood monocytes stimulated with bacterial lipopolysaccharide, suggesting that TNF-alpha is a major monocyte-derived fibroblast chemoattractant. The portion of the human TNF-alpha molecule responsible for its chemotactic stimulation of fibroblasts appears to reside in residues 31-68. This region is highly conserved between TNF-alpha and lymphotoxin. This peptide is not only itself chemotactic but is also able to block the chemotactic response of fibroblasts to hrTNF-alpha and vice versa, suggesting that they each mediate fibroblast migration through similar mechanisms. These data further underscore the potential importance of TNF-alpha in modulating a variety of fibroblast functions, including chemotaxis and synthesis of collagen, glycosaminoglycans, interleukin 1 alpha (IL-1 alpha) and -beta, human histocompatibility leukocyte antigen A and B antigens, collagenase, prostaglandin E2, and IL-6.     

Tumor necrosis factor (TNF) receptor shedding controls thresholds of innate immune activation that balance opposing TNF functions in infectious and inflammatory diseases

Tumor necrosis factor (TNF) is a potent cytokine exerting critical functions in the activation and regulation of immune and inflammatory responses. Due to its pleiotropic activities, the amplitude and duration of TNF function must be tightly regulated. One of the mechanisms that may have evolved to modulate TNF function is the proteolytic cleavage of its cell surface receptors. In humans, mutations affecting shedding of the p55TNF receptor (R) have been linked with the development of the TNFR-associated periodic syndromes, disorders characterized by recurrent fever attacks and localized inflammation. Here we show that knock-in mice expressing a mutated nonsheddable p55TNFR develop Toll-like receptor-dependent innate immune hyperreactivity, which renders their immune system more efficient at controlling intracellular bacterial infections. Notably, gain of function for antibacterial host defenses ensues at the cost of disbalanced inflammatory reactions that lead to pathology. Mutant mice exhibit spontaneous hepatitis, enhanced susceptibility to endotoxic shock, exacerbated TNF-dependent arthritis, and experimental autoimmune encephalomyelitis. These results introduce a new concept for receptor shedding as a mechanism setting up thresholds of cytokine function to balance resistance and susceptibility to disease. Assessment of p55TNFR shedding may thus be of prognostic value in infectious, inflammatory, and autoimmune diseases.     

急性白血病骨髓基质细胞肿瘤坏死因子α分泌活性及其意义

目的：探讨急性白血病（ＡＬ）骨髓基质细胞肿瘤坏死因子α（ＴＮＦα）分泌活性。方法：应用体外骨髓基质细胞培养法及ＴＮＦα生物活性检测法，对ＡＬ患者２０例及正常对照者１０名的骨髓基质细胞培养上清中的ＴＮＦα活性水平进行检测，并同步检测了患者血清、骨髓白血病细胞培养上清中的ＴＮＦα活性。结果：ＡＬ骨髓基质细胞形成能力较差，但其ＴＮＦα活性明显高于对照组（Ｐ＜０．０５）；少部分急性髓系白血病（ＡＭＬ）骨髓白血病细胞能自发分泌ＴＮＦα；患者血清中的ＴＮＦα活性显著高于正常对照（Ｐ＜０．００１）。结论：ＡＬ患者骨髓基质细胞存在量和质的异常，ＴＮＦα的异常分泌可能是导致ＡＬ增殖的一个重要因素     

Tumor necrosis factor alpha is a critical component of interleukin 13-mediated protective T helper cell type 2 responses during helminth infection.

In vivo manipulation of cytokine and/or cytokine receptor expression has previously shown that resistance to infection with the caecum-dwelling helminth Trichuris muris is dependent on interleukin (IL)-4 and IL-13 while susceptibility is associated with a T helper cell type 1 (Th1) cytokine response. Using gene-targeted mice deficient in tumor necrosis factor (TNF) receptor signaling and anti-TNF-alpha monoclonal antibody treatment, we have extended these studies to reveal a critical role for TNF-alpha in regulation of Th2 cytokine-mediated host protection. In vivo blockade of TNF-alpha in normally resistant mice, although not altering IL-4, IL-5, or IL-13 production in the draining lymph node, significantly delayed worm expulsion for the duration of treatment. IL-13-mediated worm expulsion in IL-4 knockout (KO) mice was also shown to be TNF-alpha dependent, and could be enhanced by administration of recombinant TNF-alpha. Furthermore, TNF receptor KO mice failed to expel T. muris, producing high levels of parasite-specific immunoglobulin G2a and the generation of a predominantly Th1 response, suggesting that the absence of TNF function from the onset of infection dramatically alters the phenotype of the response. These results provide the first demonstration of the role of TNF-alpha in regulating Th2 cytokine-mediated responses at mucosal sites, and have implications for the design of rational therapies against helminth infection and allergy.     

Tumor necrosis factor alpha is a potent synergistic factor for the proliferation of primitive human hematopoietic progenitor cells and induces resistance to transforming growth factor beta but not to interferon gamma

Since tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and transforming growth factor (TGF)-beta have all been shown to be specific inhibitors of early human hematopoiesis, we wanted to investigate the interactions of these three cytokines on very primitive human adult bone marrow CD34++CD38- hematopoietic progenitor cells, using a pre-colony-forming cell (pre-CFC) assay, which detects the effects of these cytokines on the initial phases of the differentiation of these primitive progenitors, which are unresponsive to interleukin (IL) 3 alone. Surprisingly, TNF-alpha was a very potent stimulator of the proliferation of CD34++CD38- cells and was the most potent synergistic factor for the IL-3-induced proliferation of these cells of all cytokines tested (IL-1, IL-6, granulocyte colony-stimulating factor, kit ligand). TNF-alpha was the only cytokine that, as a single added factor, induced substantial proliferation in CD34++CD38- cells in the presence of IL-3, except for kit ligand, which induced very limited proliferation. TNF-alpha, moreover, induced a high degree of resistance to the inhibitory effects of TGF-beta in a dose-dependent way. The inhibitory effects of IFN-gamma, however, were not affected by the presence of TNF-alpha. We hypothesize that in situations of the hematopoietic stress, TNF-alpha may abrogate the inhibitory effect of ambient TGF-beta in the bone marrow microenvironment to allow primitive stem cells to proliferate and differentiate in response to an increased demand for mature blood cells.     

Tumor necrosis factor/cachectin stimulates peritoneal macrophages, polymorphonuclear neutrophils, and vascular endothelial cells to synthesize and release platelet-activating factor

Murine tumor necrosis factor (mTNF) stimulates production of platelet-activating factor (PAF) by cultured rat peritoneal macrophages in amounts comparable to those formed during treatment with the calcium ionophore A23187 or phagocytosis of zymosan. The cell-associated PAF that was released into the medium was identical to synthetic PAF, as determined with physicochemical, chromatographic, and enzymatic assays. Furthermore, de novo synthesis of PAF by macrophages was demonstrated by the incorporation of radioactive precursors such as [3H]acetyl-coenzyme A or [3H]2-lyso-PAF. Macrophages incubated with mTNF for 4 h synthesized PAF only during the first h of treatment. At this time, the amount of cell-associated PAF was approximately equal to that released into the medium. The cell-associated PAF decreased afterwards, whereas that in the medium did not correspondingly increase, suggesting that some PAF was being degraded. The response of rat macrophages to different doses of mTNF and human TNF (hTNF) was examined. Maximal synthesis of PAF was obtained with 10 ng/ml of mTNF and 50 ng/ml of hTNF. This finding may be explained by a lower affinity of hTNF for TNF receptors of rat cells. The hTNF stimulated production of PAF by human vascular endothelial cells cultured from the umbilical cord vein. The time course of PAF synthesis was slower than that observed with macrophages, with maximal production between 4 and 6 h of treatment. Optimal synthesis of PAF was obtained with 10 ng/ml of hTNF. Only 20-30% of the PAF synthesized by endothelial cells was released into the medium, even after several hours of incubation. Synthesis of PAF in response to TNF was also detected in rat polymorphonuclear neutrophils, but not in human tumor cells and dermal fibroblasts. Therefore, production of PAF is a specialized response that is transient in macrophages continuously treated with TNF, and that appears to be controlled by unidentified regulatory mechanisms.     

Uncoupling the proinflammatory from the immunosuppressive properties of tumor necrosis factor (TNF) at the p55 TNF receptor level: implications for pathogenesis and therapy of autoimmune demyelination

Multiple sclerosis (MS) is a disabling inflammatory demyelinating disease of the central nervous system, considered to result from self-reactivity to myelin antigens. Tumor necrosis factor (TNF) and the p55 TNF receptor (TNFR) have been strongly implicated in MS pathogenesis. We reveal in this study a dual role for TNF in experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. In addition to its well-established proinflammatory effects, TNF exhibits potent immunosuppressive properties, providing one possible explanation for the immune and disease activating effect of anti-TNF treatment of MS. We show that in TNF-deficient mice, myelin-specific T cell reactivity fails to regress and expansion of activated/memory T cells is abnormally prolonged, leading to exacerbated EAE. Strikingly, immunosuppression by TNF and protection against EAE does not require the p55 TNFR, whereas the same receptor is necessary for the detrimental effects of TNF during the acute phase of the disease. Thus, blocking the function of the p55 TNFR in autoimmune demyelination may inhibit the noxious proinflammatory activities of TNF without compromising its immunosuppressive properties.     

Unusually large von Willebrand factor multimers increase adhesion of sickle erythrocytes to human endothelial cells under controlled flow

The interactions of normal erythrocytes and erythrocytes from patients having hemoglobin S hemoglobinopathies with normal human endothelial cells (EC) were investigated under flow conditions. When EC supernatant, containing 2.8-11.0 U/dl of von Willebrand factor (vWF) antigen and vWF multimeric forms larger than those present in normal plasma, was the red blood cell (RBC)-suspending medium instead of serum-free medium (SFM), the adhesion of sickle RBC, but not normal RBC, to endothelial cells was greatly increased (range of enhancement of sickle RBC adhesion, 2- to 27-fold). Adhesion of sickle RBC to endothelial cells was reduced to near serum-free levels when EC supernatant was immunologically depleted of vWF forms. Sickle RBC suspended in SFM containing 200 U/dl of purified vWF multimers of the type found in normal human plasma or 300 micrograms/ml human fibronectin were only slightly more adhesive to endothelial cells than sickle RBC suspended in SFM alone. These data indicate that unusually large vWF multimers produced by endothelial cells are potent mediators of the adhesion of sickle erythrocytes to endothelial cells. Vaso-occlusive crises in sickle cell anemia may be caused, at least in part, by adhesive interactions between the abnormal surfaces of sickle RBC and the endothelium after the release of unusually large vWF multimeric forms from stimulated or damaged endothelial cells.     

Tumor necrosis factor-alpha inhibits stem cell factor-induced proliferation of human bone marrow progenitor cells in vitro. Role of p55 and p75 tumor necrosis factor receptors.

Stem cell factor (SCF), a key regulator of hematopoiesis, potently synergizes with a number of hematopoietic growth factors. However, little is known about growth factors capable of inhibiting the actions of SCF. TNF-alpha has been shown to act as a bidirectional regulator of myeloid cell proliferation and differentiation. This study was designed to examine interactions between TNF-alpha and SCF. Here, we demonstrate that TNF-alpha potently and directly inhibits SCF-stimulated proliferation of CD34+ hematopoietic progenitor cells. Furthermore, TNF-alpha blocked all colony formation stimulated by SCF in combination with granulocyte colony-stimulating factor (CSF) or CSF-1. The synergistic effect of SCF observed in combination with GM-CSF or IL-3 was also inhibited by TNF-alpha, resulting in colony numbers similar to those obtained in the absence of SCF. These effects of TNF-alpha were mediated through the p55 TNF receptor, whereas little or no inhibition was signaled through the p75 TNF receptor. Finally, TNF-alpha downregulated c-kit cell-surface expression on CD34+ bone marrow cells, and this was predominantly a p55 TNF receptor-mediated event as well.     

The immunocytokine scFv23/TNF sensitizes HER-2/neu-overexpressing SKBR-3 cells to tumor necrosis factor (TNF) via up-regulation of TNF receptor-1

Overexpression of HER-2/neu confers cellular resistance to tumor necrosis factor (TNF)-mediated cytotoxicity to SKBR-3 breast cancer cell lines. To understand the correlation between HER-2/neu expression and TNF resistance, we examined the unique signaling pathways associated with the cytotoxic effects of the immunocytokine scFv23/TNF, recombinant single-chain antibody fusion constructs containing TNF and targeting HER-2/neu, in TNF-resistant SKBR-3-LP cells. We found that treatment of HER-2/neu-overexpressing SKBR-3-LP cells with scFv23/TNF resulted in a 5- to 7-fold higher level of TNF receptor-1 expression 48 hours after exposure. In addition, treatment of SKBR-3-LP cells with scFv23/TNF resulted in down-regulation of Akt phosphorylation and induced apoptosis through cleavage of caspase-8, caspase-3, and poly(ADP-ribose) polymerase. ScFv23/TNF-induced cytotoxicity was inhibited by blocking of the binding of the TNF component of scFv23/TNF to TNF receptor-1 and was dependent on activation of caspase-8 and caspase-3. These results indicate that the immunocytokine scFv23/TNF sensitizes TNF-resistant HER-2/neu-overexpressing SKBR-3-LP cells to TNF-induced apoptosis via the overexpression of TNF receptor-1 and suggest that the overexpression of TNF receptor-1 plays a crucial role in TNF sensitivity in HER-2/neu-overexpressing cancer cells. ScFv23/TNF targeting the HER-2/neu may be an effective cytotoxic agent against HER-2/neu-overexpressing cancer cells, which are inherently resistant to TNF.     

Adhesion of human basophils, eosinophils, and neutrophils to interleukin 1-activated human vascular endothelial cells: contributions of endothelial cell adhesion molecules

Cytokines such as interleukin 1 (IL-1) promote adhesiveness in human umbilical vein endothelial cells for leukocytes including basophils, eosinophils, and neutrophils, and induce expression of adherence molecules including ICAM-1 (intercellular adhesion molecule-1), ELAM-1 (endothelial-leukocyte adhesion molecule-1), and VCAM-1 (vascular cell adhesion molecule-1). In the present study, blocking monoclonal antibodies (mAb) recognizing ICAM-1, ELAM-1, and VCAM-1 have been used to compare their roles in IL-1-induced adhesion of human basophils, eosinophils, and neutrophils. IL-1 treatment of endothelial cell monolayers for 4 hours induced a four- to eight-fold increase in adhesion for each cell type. Treatment of endothelial cells with either anti-ICAM-1 or anti-ELAM-1 mAb inhibited IL-1-induced adherence of each cell type. In contrast, treatment with anti-VCAM-1 mAb inhibited basophil and eosinophil (but not neutrophil) adhesion, and was especially effective in blocking eosinophil adhesion. The effects of these mAb were at least additive. Indirect immunofluorescence and flow cytometry demonstrated expression of VLA-4 alpha (very late activation antigen-4 alpha, a counter-receptor for VCAM-1) on eosinophils and basophils but not on neutrophils. These data document distinct roles for ICAM-1, ELAM-1, and VCAM-1 during basophil, eosinophil, and neutrophil adhesion in vitro, and suggest a novel mechanism for the recruitment of eosinophils and basophils to sites of inflammation in vivo.     

Recombinant human interferon-inducible protein 10 is a chemoattractant for human monocytes and T lymphocytes and promotes T cell adhesion to endothelial cells

The human cytokine interferon-inducible protein 10 (IP-10) is a small glycoprotein secreted by activated T cells, monocytes, endothelial cells, and keratinocytes, and is structurally related to a family of chemotactic cytokines called chemokines. Although this protein is present in sites of delayed-type hypersensitivity reactions and lepromatous leprosy lesions, the biological activity of IP-10 remains unknown. We report here that recombinant human IP-10 stimulated significant in vitro chemotaxis of human peripheral blood monocytes but not neutrophils. Recombinant human IP-10 also stimulated chemotaxis of stimulated, but not unstimulated, human peripheral blood T lymphocytes. Phenotypic analysis of the stimulated T cell population responsive to IP-10 demonstrated that stimulated CD4+ and CD29+ T cells migrated in response to IP-10. This resembles the biological activity of the previously described T cell chemoattractant RANTES. Using an endothelial cell adhesion assay, we demonstrated that stimulated T cells pretreated with optimal doses of IP-10 exhibited a greatly enhanced ability to bind to an interleukin 1-treated endothelial cell monolayer. These results demonstrate that the IP-10 gene encodes for an inflammatory mediator that specifically stimulates the directional migration of T cells and monocytes as well as potentiates T cell adhesion to endothelium.