Endothelial cell activation
Authors: Barbara J. Ballermann
Journal: Kidney International (1998)

A 51-year-old white woman was admitted to the Johns Hopkins Hospital with a three-day history of diarrhea characterized by three to four loose bowel movements per day associated with nausea, vomiting, abdominal cramping, fever, epistaxis, and diminished urine output. During the 24 hours prior to admission, she had produced no urine. She denied dysuria, hematuria, or flank pain. She had not noted either a rash or joint or muscle pains, nor had she had a skin or pharyngeal infection. Aside from well-controlled hypertension and a history of an uncomplicated percutaneous coronary angioplasty two years earlier, she had been well before the onset of this illness. She denied any history of urinary tract symptoms or abnormalities. No other members of her family had fallen ill. The patient had been seen for a routine evaluation one month prior to the onset of the present illness. At that time, her blood urea nitrogen was 13 mg/dl; the serum creatinine was 0.8 mg/dl with normal electrolytes. The white blood cell count was 5.5 × 106/ml; hemoglobin, 13.3 g/dl with a hematocrit of 41%. The platelet count was 291 × 106/ml. At the time of admission, the patient was pale, alert, and in no acute distress. Her blood pressure was 148/85 mm Hg; heart rate, 85 beats/min; respiratory rate, 22 breaths/min; temperature 39°C. A pronounced diffuse petechial rash was noted. No adenopathy was present, nor were muscle or joint tenderness. Examination revealed a normal heart and lungs. The abdomen was soft and had mild, diffuse tenderness without rebound tenderness. Rectal examination was normal; stool was positive for occult blood. There was no flank tenderness. No peripheral edema was noted. At no time during her hospital stay was there any hemodynamic compromise. At the time of admission, the blood urea nitrogen was 110 mg/dl; serum creatinine, 11.3 mg/dl; serum sodium, 131 mEq/liter; and serum potassium, 4.9 mEq/liter. The serum bicarbonate concentration was 19 mEq/liter. Hemoglobin was 10.1 g/dl with a hematocrit of 28.2%. The platelet count was 29 × 106/ml. The prothrombin time and partial thromboplastin time were normal. No fibrin degradation products were present. The white blood cell count was 10.7 × 106/ml, with 53% polymorphonuclear neutrophils, 23% bands, 14% lymphocytes, 7% basophils, and 3% atypical lymphocytes. The serum lactate dehydrogenase concentration was 8000 mg/dl and the blood smear showed numerous schistocytes. Catheterization produced 15 ml of urine. The unspun specimen showed numerous white blood cells and 2–5 red blood cells/high-powered field; bacteria were present. Renal ultrasound examination revealed two kidneys of normal size, without evidence of obstruction. Within the first 24 hours of admission, gram-negative rods grew in 3 blood cultures and in the urine culture. The organisms later were identified as Enterobacter aerogenes with broad antibiotic sensitivity. The patient was given antibiotics. Hemodialysis every other day was initiated. Her fever resolved within 24 hours and all evidence of hemolysis ceased within 4 days. Thrombocytopenia improved; the platelet count returned to normal one week after institution of antibiotic therapy. However, complete anuria persisted. On day 10 of her hospital stay, a diagnostic percutaneous renal biopsy was performed. The biopsy, which will be discussed in detail by Dr. Racusen, showed evidence of acute infectious interstitial nephritis (pyelonephritis). In addition, findings on electron microscopy were consistent with acute thrombotic microangiopathy. Three days after the renal biopsy was performed, the patient produced small amounts of urine containing many white blood cells. The urine output continued to increase, and the urinalysis showed copious white blood cells throughout her hospital stay. Dialysis was discontinued, and the patient was discharged 10 days after the renal biopsy. Followup one week later showed a serum creatinine of 2.0 mg/dl and a blood urea nitrogen concentration of 18 mg/dl. She failed to keep further appointments. This case demonstrates the clinical features of both pro-coagulant and pro-inflammatory endothelial cell activation. Massive mobilization of von Willebrand factor and P-selectin by calcium-mobilizing agonists is likely to play the predominant role in platelet thrombus formation, so common in patients with thrombotic microangiopathy, while recruitment of inflammatory cells is mediated by a different, NFκB-dependent mechanism mechanism, reflected in this case by interstitial leukocyte infiltration. DR. LORRAINE C. RACUSEN (Associate Professor of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA): The biopsy specimen consists mainly of cortex, with a small amount of medulla. At low power, the very cellular appearance of the cortical and medullary interstitium is immediately evident. Glomeruli are not hypercellular, but there is periglomerular inflammation. At higher power, the interstitial infiltrate consists predominantly of mononuclear cells, with plasma cells, lymphocytes, and monocyte/macrophages. Many polymorphonuclear leukocytes are also found in the interstitium Figure 1A; in some areas these are very numerous, forming mini-abscesses. In addition, occasional foci of eosinophil accumulation are observed. Scattered throughout the specimen are many large and potentially obstructing cellular casts Figure 1A containing polymorphonuclear leukocytes within the tubules. There is localized tubular epithelial cell injury with vacuolization, tubular cell loss, and sloughing of epithelial cells into the lumen. Special stains show intrusion of inflammatory cells through the basement membrane into tubules, at times lifting the epithelial cells from the basement membrane. Prominent interstitial edema is present without evidence of fibrosis. Examination of glomeruli shows normal cellularity and open capillary loops. The silver stain shows some areas of localized interposition. Subtle endothelial cell enlargement with some edema and vacuolization is evident. Patchy arteriolar smooth muscle cell vacuolization is also observed. Immunofluorescence showed no deposition of immunoglobulins or complement components within the glomeruli. Ultrastructural examination shows no glomerular cell proliferation, inflammatory cells, or electron-dense deposits. However, there is widespread evidence of glomerular endothelial and epithelial cell injury Figure 1B. Endothelial cell swelling is evident both at the capillary loop hilum and around the circumference of the glomerular capillaries. The normal endothelial cell fenestrae have been lost. In several areas, endothelial cells have lifted away from the basement membrane, and flocculent material has accumulated between the cells and the glomerular capillary basement membrane. Also evident are extensive epithelial cell foot process effacement and some microvillous transformation of epithelial cells. The changes on biopsy are consistent with a severe interstitial nephritis, probably of infectious etiology. The glomerular changes are consistent with endothelial cell activation. This type of endothelial cell injury typically is seen in thrombotic microangiopathy, although the changes are less severe than those usually seen in the hemolytic-uremic syndrome. DR. BARBARA J. BALLERMANN (Associate Professor of Medicine, Johns Hopkins University School of Medicine): My discussion today addresses the mechanisms whereby endothelial cell activation by bacterial toxins and inflammatory mediators contributed to the dramatic presentation and clinical course of this patient. Endothelium is the principal barrier to cell movement from the circulation into tissues and usually serves an anticoagulant function. Immune injury often prompts endothelial cell swelling and vacuolization. Such ultrastructural changes are associated with increased expression of leukocyte adhesion molecules, chemokine elaboration, and augmented procoagulant activity. A good example of the ultrastructural appearance of activated glomerular capillary endothelial cells is shown in the electron micrograph of the case presented today Figure 1B. Glomerular endothelial cell swelling is a nonspecific reaction, although we have known for 3 decades that in the hemolytic-uremic syndrome[1VITSKY B.H. SUZUKI Y. STRAUSS L. CHURG J. The hemolytic-uremic syndrome: a study of renal pathologic alterations.Am J Pathol. 1969; 57: 627-647PubMed Google Scholar] and pre-eclampsia[2FAITH G.C. TRUMP B.F. The glomerular capillary wall in human kidney disease: acute glomerulonephritis, systemic lupus erythematosus, and preeclampsia-eclampsia. Comparative electron microscopic observations and a review.Lab Invest. 1966; 15: 1682-1719PubMed Google Scholar] these changes can be severe enough to reduce capillary perfusion. Activation of glomerular endothelium in immune-complex-mediated proliferative glomerulonephritis occurs in areas of subendothelial cell immune-complex or antibody deposition, where evidence for endothelial cell proliferation is also frequently detected[3FISH A.J. HERDMAN R.C. MICHAEL A.F. PICKERING R.J. GOOD R.A. Epidemic acute glomerulonephritis associated with type 49 streptococcal pyoderma. II. Correlative study of light, immunofluorescent and electron microscopic findings.Am J Med. 1970; 48: 28-39Abstract Full Text PDF PubMed Scopus (45) Google Scholar]. The clinical observation of platelet consumption and formation of schistocytes in cases of thrombotic microangiopathy results from activation of endothelial cell pro-coagulant activity. Leukocyte influx into the kidney in response to infection, or into glomeruli in cases of glomerulonephritis, reflects activation of endothelial cell leukocyte recruitment mechanisms. Local activation of pro-coagulant and leukocyte recruitment mechanisms coexist in most cases of inflammatory endothelial cell activation, whereas procoagulant mechanisms predominate in the thrombotic microangiopathies. The case presented today lends itself nicely to the discussion of both phenomena, given the concomitant evidence for acute infectious interstitial nephritis with massive infiltration of the kidneys by inflammatory cells and the clinical and electron microscopic evidence for thrombotic microangiography. As I stated, my goal is to provide a comprehensive overview of the mechanisms of endothelial cell activation. Endothelial cell activation can be direct, for example, when anti-endothelial cell antibodies result in complement fixation at the endothelial cell surface, or when bacterial toxins or toxic pharmacologic agents act on endothelial cells. Activation also can result from the release of cytokines by neighboring cells, for instance, in response to infection or antigen-antibody complex formation. Circulating anti-endothelial cell antibodies are sometimes observed in patients with vasculitis[4WANG C.R. LIU M.F. TSAI R.T. CHUANG C.Y. CHEN C.Y. Circulating intercellular adhesion molecules-1 and autoantibodies including anti-endothelial cell, anti-cardiolipin, and anti-neutrophil cytoplasma antibodies in patients with vasculitis.Clin Rheumatol. 1993; 12: 375-380Crossref PubMed Scopus (24) Google Scholar], scleroderma[5HOLT C.M. LINDSEY N. MOULT J. MALIA R.G. GREAVES M. HUME A. ROWELL N.R. HUGHES P. Antibody-dependent cellular cytotoxicity of vascular endothelium: Characterization and pathogenic association in systemic sclerosis.Clin Exp Immunol. 1989; 78: 359-365PubMed Google Scholar], and possibly also antineutrophil-cytoplasmic-antibody (ANCA)-associated vasculitis[6CHAN T.M. FRAMPTON G. JAYNE D.R. PERRY G.J. LOCKWOOD C.M. CAMERON J.S. Clinical significance of anti-endothelial cell antibodies in systemic vasculitis: a longitudinal study comparing anti-endothelial cell antibodies and anti-neutrophil cytoplasm antibodies.Am J Kidney Dis. 1993; 22: 387-392Abstract Full Text PDF PubMed Scopus (89) Google Scholar]. Although endothelial cells do not express the most common ANCA antigens, proteinase 3 and myeloperoxidase, these enzymes can associate non-covalently with the glycocalyx of endothelial-cell plasma membrane after being released from degranulating neutrophils[7SAVAGE C.O. GASKIN G. PUSEY C.D. PEARSON J.D. Anti-neutrophil cytoplasm antibodies can recognize vascular endothelial cell-bound anti-neutrophil cytoplasm antibody-associated autoantigens.Exp Nephrol. 1993; 1: 190-195PubMed Google Scholar], where they then are subject to ANCA binding with consequent complement-dependent endothelial cell lysis. The display of ANCA antigens at the plasma membrane surface of active neutrophils results in an oxidative burst[8SAVAGE C.O.S. POTTINGER B.E. GASKIN G. PUSEY C.D. PEARSON J.D. Autoantibodies developing to myeloperoxidase and proteinase 3 in systemic vasculitis stimulate neutrophil cytotoxicity toward cultured endothelial cells.Am J Pathol. 1992; 141: 335-342PubMed Google Scholar]. Under those circumstances, endothelial cell injury is caused by oxygen-free radicals, proteases, and lipid mediators. Binding of anti-endothelial cell antibodies to their target antigens[9CAMUSSI G. BIESECKER G. CALDWELL P.R. BIANCONE L. ANDRES G. BRENTJENS J.R. Role of the membrane attack complex of complement in lung injury mediated by antibodies to endothelium.Int Arch Allergy Appl Immunol. 1993; 102: 216-223Crossref Scopus (5) Google Scholar], subendothelial cell immune-complex deposition, for instance, in SLE and poststreptococcal glomerulonephritis[10TATENO S. KOBAYASHI Y. SHIGEMATSU H. HIKI Y. Study of lupus nephritis: Its classification and the significance of subendothelial deposits.Q J Med. 1983; 295: 907-918Google Scholar,11SORGER K. GESSLER U. HUBNER F.K. KOHLER H. SCHULZ W. STUHLINGER W. THOENES G.H. THOENES W. Subtypes of postinfectious glomerulonephritis: Synopsis of clinical and pathological features.Clin Nephrol. 1982; 17: 114-128PubMed Google Scholar], or interaction of antibodies with the glomerular basement membrane[12WILSON C.B. DIXON F.J. Antiglomerular basement membrane antibody-induced glomerulonephritis.Kidney Int. 1973; 3: 74-89Abstract Full Text PDF PubMed Scopus (370) Google Scholar] leads to complement fixation and complement-mediated endothelial cell injury[13SCHUMAKER V.N. ZAVODSZKY P. POON P.H. Activation of the first component of complement.Annu Rev Immunol. 1987; 5: 21-42Crossref PubMed Scopus (125) Google Scholar]. Some of the products of the activated complement cascade interact directly with endothelial cells to activate endothelial cell procoagulant and leukocyte adhesion functions Figure 2A. Receptors for the first component of complement, C1q[13SCHUMAKER V.N. ZAVODSZKY P. POON P.H. Activation of the first component of complement.Annu Rev Immunol. 1987; 5: 21-42Crossref PubMed Scopus (125) Google Scholar], are expressed by leukocytes, platelets, and mesangial and endothelial cells[14VANDEN DOBBELSTEEN M.E. VANDER WOUDE F.J. SCHROEIJERS W.E. KLAR-MOHAMAD N. VAN ES L.A. DAHA M.R. C1Q, a subunit of the first component of complement, enhances the binding of aggregated IgG to rat renal mesangial cells.J Immunol. 1993; 151: 4315-4324Google Scholar,15PEERSCHKE E.I. MALHOTRA R. GHEBREHIWET B. REID K.B. WILLIS A.C. SIM R.B. Isolation of a human endothelial cell C1q receptor (C1qR).J Leukoc Biol. 1993; 53: 179-184PubMed Google Scholar]. In myeloid and mesangial cells, C1q receptors facilitate Fc receptor-dependent immune-complex phagocytosis and oxygen-free-radical formation[16SIM R.B. REID K.B.M. C1: molecular interactions with activating systems.Immunol Today. 1991; 12: 307-311Abstract Full Text PDF PubMed Scopus (74) Google Scholar]. In endothelial cells, which only express Fc receptors when primed by interferon γ[17RYAN U.S. SCHULTZ D.R. DEL VECCHIO P.J. RYAN J.W. Endothelial cells of bovine pulmonary artery lack receptors for C3b and for the Fc portion of immunoglobulin G.Science. 1980; 208: 748-749Crossref PubMed Scopus (18) Google Scholar,18RYAN U.S. SCHULTZ D.R. RYAN J.W. Fc and C3b receptors on pulmonary endothelial cells: Induction by injury.Science. 1981; 214: 557-558Crossref PubMed Scopus (66) Google Scholar], antigen-antibody-fixed C1q nevertheless stimulates endothelial cell expression of the neutrophil adhesion molecules E-selectin, ICAM-1, and VCAM-1 by activating C1q receptors[19LOZADA C. LEVIN R.I. HUIE M. HIRSCHHORN R. NAIME D. WHITLOW M. RECHT P.A. GOLDEN B. CRONSTEIN B.N. Identification of C1q as the heat-labile serum cofactor required for immune complexes to stimulate endothelial expression of the adhesion molecules E-selectin and intercellular and vascular cell adhesion molecules 1.Proc Natl Acad Sci USA. 1995; 92: 8378-8382Crossref PubMed Scopus (117) Google Scholar], even in the absence of other co-stimulants. Activation of the classical complement cascade by antigen-bound IgG and IgM antibodies releases the anaphylatoxins C3a, C4a, and C5a, which are produced by proteolytic cleavage of the inactive C4, C3, and C5 complement components. In endothelial cells, activation of C5a receptors rapidly mobilizes P-selectin to the cell surface and induces von Willebrand factor (vWF) secretion[20FOREMAN K.E. VAPORCIYAN A.A. BONISH B.K. JONES M.L. JOHNSON K.J. GLOVSKY M.M. EDDY S.M. WARD P.A. C5a-induced expression of P-selectin in endothelial cells.J Clin Invest. 1994; 94: 1147-1155Crossref PubMed Scopus (375) Google Scholar]. Both pre-formed vWF and P-selectin, stored in endothelial cell Weibel-Palade bodies, are rapidly mobilized by several calcium-mobilizing agonists in addition to C5a, for instance, thrombin, histamine, and leukotriene C4[21WAGNER D.D. The Weibel-Palade body: the storage granule for von Willebrand factor and P-selectin.Thromb Haemost. 1993; 70: 105-110Crossref PubMed Google Scholar]. The ultimate product of complement activation is the membrane attack complex C5b-9, which forms large pores in the plasma membrane[22MULLER-EBERHARD H.J. The membrane attack complex.Annu Rev Immunol. 1986; 4: 503-528Crossref PubMed Scopus (351) Google Scholar]. In patients with vasculitis, C5b-9 has been localized to endothelial cells[23BOOM B.W. MOMMAAS M. DAHA M.R. VERMEER B.J. Complement-mediated endothelial cell damage in immune complex vasculitis of the skin: ultrastructural localization of the membrane attack complex.J Invest Dermatol. 1989; 93: 68S-72SAbstract Full Text PDF PubMed Scopus (18) Google Scholar], and C5b-9 mediates endothelial cell destruction following xenotransplantation[24ROLLINS S.A. MATIS L.A. SPRINGHORN J.P. SETTER E. WOLFF D.W. Monoclonal antibodies directed against human C5 and C8 block complement-mediated damage of xenogeneic cells and organs.Transplantation. 1995; 60: 1284-1292Crossref PubMed Scopus (37) Google Scholar]. Large quantities of C5b-9 produce frank endothelial cell lysis[25SUTTORP N. BHAKDI S. Terminal complement complex and endothelial cells.Z Kardiol. 1989; 78: 140-142PubMed Google Scholar]. Two powerful inhibitors of membrane-attack-complex formation, CD59 and HRF (homologous restriction factor) are expressed by endothelial cells, including renal glomerular and peritubular endothelial cells[26LEHTO T. HONKANEN E. TEPPO A.M. MERI S. Urinary excretion of protectin (CD59), complement SC5b-9 and cytokines in membranous glomerulonephritis.Kidney Int. 1995; 47: 1403-1411Abstract Full Text PDF PubMed Scopus (49) Google Scholar, 27NOSE M. KATOH M. OKADA N. KYOGOKU M. OKADA H. Tissue distribution of HRF20, a novel factor preventing the membrane attack of homologous complement, and its predominant expression on endothelial cells in vivo.Immunology. 1990; 70: 145-149PubMed Google Scholar, 28QUIGG R.J. MORGAN B.P. HOLERS V.M. ADLER S. SNEED III, A.E. LO C.F. Complement regulation in the rat glomerulus: Crry and CD59 regulate complement in glomerular mesangial and endothelial cells.Kidney Int. 1995; 48: 412-421Abstract Full Text PDF PubMed Scopus (46) Google Scholar]. These proteins protect endothelial cells from complement-mediated damage in species-specific fashion. Indeed, human CD59 protects against xenoantibody-mediated endothelial cell lysis. This finding suggests that the xenotransplantation barrier might be overcome, in part, by using organs from animals transgenic for human CD59[29CHARREAU B. CASSARD A. TESSON L. LE MAUFF B. NAVENOT J.M. BLANCHARD D. LUBLIN D. SOULILLOU J.P. ANEGON I. Protection of rat endothelial cells from primate complement-mediated lysis by expression of human CD59 and/or decay-accelerating factor.Transplantation. 1994; 58: 1222-1229PubMed Google Scholar]. Inhibitors of earlier steps in the complement-activation cascade, including decay accelerating factor, which inhibits C3 and C5 convertase function, are also expressed by endothelial cells and are similarly protective against complement activation[30BROOIMANS R.V. VAN WIERINGEN P.A. VAN ES L.A. DAHA M.R. Relative roles of decay-accelerating factor. membrane cofactor protein, and CD59 in the protection of human endothelial cells against complement-mediated lysis.Eur J Immunol. 1992; 22: 3135-3140Crossref PubMed Scopus (69) Google Scholar]. Complement activation at the endothelial surface does not always lead to cell lysis, probably because of these endothelial complement inhibitors. Consequently, sublytic effects of C5b-9 have been described, most prominent among them the induction of procoagulant activity[31SIMS P.J. WIEDMER T. Induction of cellular procoagulant activity by the membrane attack complex of complement.Semin Cell Biol. 1995; 6: 275-282Crossref PubMed Scopus (47) Google Scholar]. The C5b-9 complex stimulates vWF release and cell-surface P-selectin expression[32HATTORI R. HAMILTON K.K. MCEVER R.P. SIMS P.J. Complement proteins C5b-9 induce secretion of high molecular weight multimers of endothelial von Willebrand factor and translocation of granule membrane protein GMP-140 to the cell surface.J Biol Chem. 1989; 264: 9053-9060Abstract Full Text PDF PubMed Google Scholar] and markedly increases endothelial cell tissue factor production Figure 2A[33SAADI S. HOLZKNECHT R.A. PATTE C.P. STERN D.M. PLATT J.L. Complement-mediated regulation of tissue factor activity in endothelium.J Exp Med. 1995; 182: 1807-1814Crossref PubMed Scopus (229) Google Scholar]. In addition, C5b-9 stimulates E-selectin and ICAM-1 expression[34KILGORE K.S. SHEN J.P. MILLER B.F. WARD P.A. WARREN J.S. Enhancement by the complement membrane attack complex of tumor necrosis factor-alpha-induced endothelial cell expression of E-selectin and ICAM-1.J Immunol. 1995; 155: 1434-1441PubMed Google Scholar]. Tumor necrosis factor α (TGFα) and interleukin-1β (IL-1β) are central mediators of endothelial cell activation. They stimulate endothelial cells to secrete chemokines and express leukocyte-adhesion molecules, and they turn endothelium into a procoagulant surface[35WENZEL U.O. ABBOUD H.E. Chemokines and renal disease.Am J Kidney Dis. 1995; 26: 982-994Abstract Full Text PDF PubMed Scopus (62) Google Scholar,36LUSCINSKAS F.W. GIMBRONE M.A. Endothelial-dependent mechanisms in chronic inflammatory leukocyte recruitment.Annu Rev Med. 1996; 47: 413-421Crossref PubMed Scopus (151) Google Scholar]. Both TNFα and IL-1β are secreted by tissue macrophages and other resident cells Figure 2B in response to bacterial endotoxin (lipopolysaccharide, LPS); this response is markedly augmented by interferon[37SHAKHOV A.N. COLLART M.A. VASSALLI P. NEDOSPASOV S.A. JONGENEEL V.C. Kappa-B-type enhancers are involved in lipopolysaccharide-mediated transcriptional activation of the tumor necrosis factor-alpha gene in primary macrophages.J Exp Med. 1990; 171: 35-47Crossref PubMed Scopus (701) Google Scholar]. In addition, phagocytosis of opsonized particles, Fc receptor cross-linking[38STEIN M. GORDON S. Regulation of tumor necrosis factor (TNF) release by murine peritoneal macrophages: role of cell stimulation and specific phagocytic plasma membrane receptors.Eur J Immunol. 1991; 21: 431-437Crossref PubMed Scopus (72) Google Scholar], IgG and IgA immune complexes[39LAUFER J. BOICHIS H. FARZAM N. PASSWELL J.H. IgA and IgG immune complexes increase human macrophage C3 biosynthesis.Immunology. 1995; 84: 207-212Google Scholar], and C5a[40OKUSAWA Z. YANCEY K.B. VANDER MEER J.W.M. ENDRES S. LONNEMANN G. HEFTER K. FRANK M.M. BURKE J.F. DINARELLO C.A. GELFAND J.A. C5a stimulates secretion of tumor necrosis factor from human mononuclear cells in vitro. Comparison with secretion of interleukin 1β and interleukin 1α.J Exp Med. 1988; 168: 443-448Crossref PubMed Scopus (175) Google Scholar] all stimulate TNFα secretion. TNFα is also secreted by T-lymphocytes during the process of T-cell-receptor engagement with major histocompatibility complex (MHC) class-II bound antigens[41TREDE N.S. HEHA R.S. CHATILA T. Transcriptional activation of IL-1β and tumor necrosis factor-α genes by MHC class II ligands.J Immunol. 1991; 146: 2310-2315PubMed Google Scholar] and by activated polymorphonuclear neutrophils[42DJEU J. SERBOUSEK D. BANCHARD D.K. Release of tumor necrosis factor by human polymorphonuclear leukocytes.Blood. 1990; 76: 1405-1409Crossref PubMed Google Scholar]. Interleukin-1β is synthesized by monocyte/macrophages; potent stimuli for its synthesis are LPS and macrophage contact with CD4+ T-cells[43DINARELLO C.A. Role of interleukin-1 in infectious diseases.Immunol Rev. 1992; 127: 119-146Crossref PubMed Scopus (173) Google Scholar]. Also, TNFα strongly stimulates IL-1β synthesis by macrophages and by a number of other cell types, including endothelial cells. Studies also have shown the presence of TNFα and IL-1β in resident glomerular cells in glomerulonephritis both in experimental animals and in patients[44BAUD L. OUDINET J.P. BENS M. NOE L. PERALDI M.N. RONDEAU E. ETIENNE J. ARDAILLOU R. Production of tumor necrosis factor by rat mesangial cells in response to bacterial lipopolysaccharide.Kidney Int. 1989; 35: 1111-1118Abstract Full Text PDF PubMed Scopus (177) Google Scholar, 45MALIDE D. RUSSO P. BENDAYAN M. Presence of tumor necrosis factor alpha and interleukin-6 in renal mesangial cells of lupus nephritis patients.Hum Pathol. 1995; 26: 558-564Abstract Full Text PDF PubMed Scopus (110) Google Scholar, 46BAUD L. ARDAILLOU R. Tumor necrosis factor in renal injury.Miner Electrolyte Metab. 1995; 21: 336-341PubMed Google Scholar]. In the patient presented today, the induction of inflammatory cytokines by bacterial LPS probably was responsible, at least in part, for endothelial cell-dependent recruitment of lymphocytes into the interstitium. Whether cytokine production was sufficient to explain activation of glomerular endothelial cells or whether an additional, unidentified bacterial toxin participated in promoting glomerular endothelial cell procoagulant activity is not known. In endothelial cells, TNFα and IL-1β activate the nuclear transcription factor NF-κB/Rel, thereby triggering the transcription of a number of genes that control the endothelial cell inflammatory response[47COLLINS T. READ M.A. NEISH A.S. WHITLEY M.Z. THANOS D. MANIATIS T. Transcriptional regulation of endothelial cell adhesion molecules: NF-kappa B and cytokine-inducible enhancers.FASEB J. 1995; 9: 899-909Crossref PubMed Scopus (1479) Google Scholar]. Factor NF-κB/Rel is a dimeric complex consisting of NF-κB and Rel subunits, the former ∼ 50 kD, the latter ∼ 65 kD in size. The 65 kD Rel component exists preformed in endothelial cells, either bound to a larger (∼ 105 kD) precursor of NF-κB, which requires proteolytic cleavage to the ∼ 50 kD form for activation, or the 50 kD/65 kD NF-κB/Rel complex is bound to IκB-α, which masks the NF-κB nuclear targeting sequence. Processing of the 105 kD precursor of NF-κB or degradation of IκB-α via the ubiquitin/proteasome pathway results in activation[48PALOMBELLA V.J. RANDO O.J. GOLDBERG A.L. MANIATIS T. The ubiquitin-proteasome pathway is required for processing the NF-κB1 precursor protein and the activation of NF-κB.Cell. 1994; 78: 773-785Abstract Full Text PDF PubMed Scopus (1856) Google Scholar]. Phosphorylation of IκB-α targets it for degradation[47COLLINS T. READ M.A. NEISH A.S. WHITLEY M.Z. THANOS D. MANIATIS T. Transcriptional regulation of endothelial cell adhesion molecules: NF-kappa B and cytokine-inducible enhancers.FASEB J. 1995; 9: 899-909Crossref PubMed Scopus (1479) Google Scholar], and inhibition of IκB-α phosphorylation prevents NF-κB/Rel activation in endothelial cell[49CHEN C.C. ROSENBLOOM C.L. ANDERSON D.C. MANNING A.M. Selective inhibition of E-selectin, vascular cell adhesion molecule-1. and intercellular adhesion molecule-1expression by inhibitors of kappa-B-alpha phosphorylation.J Immunol. 1995; 155: 3538-3545PubMed Google Scholar]. Also, nitric oxide inhibits IκB-α degradation and NF-κB/Rel activation[50PENG H.B. LIBBY P. LIAO J.K. Induction and stabilization of I kappa B alpha by nitric oxide mediates inhibition of NF-kappa B.J Biol Chem. 1995; 270: 14214-14219Crossref PubMed Scopus (600) Google Scholar]. Upon activation, the NF-κB/Rel dimer rapidly moves to the nucleus, where it interacts with a number of promoters, among them those for leukocyte adhesion molecules E-selectin, VCAM-1, and ICAM-1, procoagulant molecules like tissue factor, and other components of the inflammatory response, for instance, the IL-8 promoter[47COLLINS T. READ M.A. NEISH A.S. WHITLEY M.Z. THANOS D. MANIATIS T. Transcriptional regulation of endothelial cell adhesion molecules: NF-kappa B and cytokine-inducible enhancers.FASEB J. 1995; 9: 899-909Crossref PubMed Scopus (1479) Google Scholar]. The actions of TNFα and IL-1β on endothelial cells are diverse, stimulating procoagulant activity, leukocyte adhesion, and mediator release Figure 2C. Leukocyte adhesion to endothelium is a necessary step for facilitating recruitment of leukocytes into areas of inflammation. Distinct adhesion molecules and chemokines regulate this process for different leukocyte subsets. Although the specific molecules involved differ depending on the type of inflamm