Microbial peptides and superantigens in the pathogenesis of autoimmune diseases of the central nervous system

Seminars in Immunology

Volumn 10, Issue 1, 1998, Pages 57-67

  Brocke, Stefan ^a   Hausmann, Stefan ^c   Steinman, Lawrence ^b   Wucherpfennig, Kai W ^c  

^a NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE   (United States)

^b STANFORD UNIVERSITY   (United States)

^c HARVARD MEDICAL SCHOOL   (United States)

Author keywords

Autoimmune disease; Microbial peptide antigens; Superantigens

Indexed keywords

BACTERIAL PROTEIN; MAJOR HISTOCOMPATIBILITY ANTIGEN CLASS 2; SUPERANTIGEN; T LYMPHOCYTE RECEPTOR;

ANTIGEN PRESENTATION; AUTOIMMUNE DISEASE; CENTRAL NERVOUS SYSTEM DISEASE; CROSS REACTION; DEMYELINATING DISEASE; HUMAN; IMMUNE RESPONSE; MOLECULAR MIMICRY; MULTIPLE SCLEROSIS; NONHUMAN; PATHOGENESIS; REVIEW; T LYMPHOCYTE ACTIVATION;

EID: 0032006777     PISSN: 10445323     EISSN: None     Source Type: Journal    
DOI: 10.1006/smim.1997.0105     Document Type: Article

References (108)

1. 1. Rapoport SI (1976) Blood-Brain Barrier in Physiology and Medicine. Raven Press, New York.
2. 2. Bradbury M (1979) The Concept of a Blood-Brain Barrier. John Wiley, Chichester.
3. 3. Wekerle H, Linington C, Lassmann H, Meyermann R (1986) Cellular immune recativity within the CNS. Trends Neurosci 6:271-277
4. 4. Mickey WF, Hsu BL, Kimura H (1991) T-lymphocyte entry into the central nervous system. J Neurosci Res 28:254-260
5. 5. Schluesener HJ, Sobel RA, Linington C, Weiner HL (1987) A monoclonal antibody against myelin oligodendrocyte glycoprotein induces relapses and demyelination in central nervous system autoimmune disease. J Immunol 139:4016-4021
6. 6. Linington C, Bradl M, Lassmann H, Brunner C, Vass K (1988) Augmentation of demyelination in rat acute allergic encephalomyelitis by circulating antibodies directed against a myelin/oligodendrocyte glycoprotein. Am J Pathol 130:443-454
7. 7. Raine CS (1991) Multiple sclerosis: a pivotal role for the T cell in lesion development. Neuropathol Appl Neurobiol 17:265-274
8. 8. Steinman L (1996) Multiple sclerosis: a coordinated immunological attack against myelin in the central nervous system. Cell 85:299-302
9. 9. Hohlfeld R (1997) Biotechnical agents for the immunotherapy of multiple sclerosis: principles, problems and perspectives. Brain 120:865-916
10. 10. Raine CS (1994a) The Dale E. McFarin Memorial Lecture: the immunology of the multiple sclerosis lesion. Ann Neurol 36:S61-S72
11. 11. Raine CS (1994b) Multiple sclerosis: immune system molecule expression in the central nervous system. J Neuropathol Exp Neurol 53:328-337
12. 12. Lassmann H (1983) Comparative neuropathology of chronic experimental allergic encephalomyelitis and multiple sclerosis. Schriftenr Neurol 25:1-135
13. 13. Lassmann H, Zimprich F, Rössler K, Vass K (1991) Inflammation in the nervous system. Basic mechanisms and immunological concepts. Rev Neurol 147:763-781
14. 14. Lassmann H, Suchanek G, Ozawa K (1994) Histopathology and the blood-cerebrospinal fluid barrier in multiple sclerosis. Ann Neurol 36:S42-S46
15. 15. Lucchinetti CF, Bruck W, Rodriguez M, Lassmann H (1996) Distinct patterns of multiple sclerosis pathology indicates heterogeneity in pathogenesis. Brain Pathol 6:259-274
16. 16. Ebers GC (1996) Genetic epidemiology of multiple sclerosis. Curr Opin Neurol 9:155-158
17. 17. McFarland HF, Martin R, McFarlin DE (1997) Genetic influences in multiple sclerosis, in Multiple Sclerosis: Clinical and Pathogenetic Basis (Raine CS, MacFarland HF, Tourtellotte WW, eds). Chapman and Hall, London
18. 18. Oksenberg JR, Seboun E, Hauser SL (1996) Genetics of demyelinating diseases. Brain Pathol 6:289-302
19. 19. Steinman L (1995) Escape from 'horror autotoxicus': pathogenesis and treatment of autoimmune disease. Cell 80:7-10
20. 20. Burns J, Rosenzweig A, Zweiman B, Lisak RP (1983) Isolation of myelin basic protein-reactive T cell lines from normal human blood. Cell Immunol 81:435-440
21. 21. Schluesener HJ, Wekerle H (1985) Au to aggressive T lymphocyte lines recognizing the encephalitogenic region of myelin basic protein: in vitro selection from unprimed rat T lymphocyte populations. J Immunol 135:3128-3133
22. 22. Genain CP, Lee-Parritz D, Nguyen MH, Massacesi L, Joshi N, Ferrante R, Hoffman K, Moseley M, Letvin NL, Hauser SL (1994) In healthy primates, circulating autoreactive T cells mediate autoimmune disease. J Clin Invest 94:1339-1345
23. 23. Kappler JW, Roehm N, Marrack P (1987) T cell tolerance by clonal elimination in the thymus. Cell 49:273-280
24. 24. Sprent J, Webb SR (1995) Intrathymic and extrathymic clonal deletion of T cells. Curr Opin Immunol 7:196-205
25. 25. Brabb T, Goldrath AW, von Dassow P, Paez A, Liggitt, HD, Goverman J (1997) Triggers of autoimmune disease in a murine TCR-transgenic model for multiple sclerosis. J Immunol 159:497-507
26. 26. Vinken PJ et al (1988) Handbook of Clinical Neurology, vol. 52:8 (revised series). Elsevier Science Publishers, Amsterdam
27. 27. Vinken PJ et al, eds (1989) Handbook of Clinical Neurology vol 56:12 (revised series). Elsevier Science Publishers, Amsterdam
28. 28. Johnson RT (1985) Viral aspects of multiple sclerosis, in Handbook of Clinical Neurology, vol. 47:3 (revised series) (Vinken PJ et al, eds), pp 319-336. Elsevier Science Publishers, Amsterdam
29. 29. Ter Meulen V, Katz M (1997) The proposed viral etiology of multiple sclerosis and related demyelinating diseases, in Multiple Sclerosis: Clinical and Pathogenetic Basis (Raine CS, MacFarland HF, Tourtellotte WW, eds), pp 287-305. Chapman and Hall, London
30. 30. Kurtzke JF (1993) Epidemiologie evidence for multiple sclerosis as an infection. Clin Microbiol Rev 6:382-427
31. 31. Panitch HS (1994) Influence of infection on exacerbations of multiple sclerosis. Ann Neurol 36:S25-S28
32. 32. Sibley WA, Bamford CR, Clark K (1985) Clinical viral infections and multiple sclerosis. Lancet 1(8441):1313-1315
33. 33. Miller SD, Karpus WJ (1994) The immunopathogensis and regulation of T-cell-mediated demyelinating diseases. Immunol Today 15:356-361
34. 34. Dal Canto MC, Melvold RW, Kim BS and Miller SD (1995) Two models of multiple sclerosis: experimental allergic encephalomyelitis and Theiler's murine encephalomyelitis virus (TMEV) infection. A pathological and immunological comparison. Microsci Res Technol 15:215-229
35. 35. Goverman J, Woods A, Larson L, Weiner LP, Hood L, Zaller DM (1993) Transgenic mice that express a myelin basic protein-specific T cell receptor develop spontaneous autoimmunity. Cell 72:551-560
36. 36. Pope JG, Karpus WJ, Vanderlugt C, ans Miller SD (1996) Flow cytometric and functional analyses of central nervous system-in filtrating cells in SJL/J mice with Theiler's virus-induced demyelinating disease. Evidence for a CD4 + T cell-mediated pathology. J Immunol 156:4050-4058
37. 37. Miller SD, McRae B, Vanderlugt CL, Nikevich KM, Pope JG, Pope L, Karpus WJ (1995) Evolution of the T-cell repertoire during the course of experimental immune-mediated demyelinating diseases. Immunol Rev 144:225-244
38. 38. Vanderlugt CJ, Miller SD (1996) Epitope spreading. Curr Opin Immunol 8:831-836
39. 39. Clark L, Fareed M, Miller SD, Merryman C, Heber-Katz E (1996) Corneal infection with herpes simplex virus type 1 leads to autoimmune response in rats. J Neurosci Res 15:770-775
40. 40. Tough DF, Sun S, Sprent J (1997) T cell stimulation in vivo by lipopolysaccharide (LPS). J Exp Med 185:2089-2094
41. 41. Segal BM, Klinman DM, Shevach EM (1997) Microbial products induce autoimmune disease by an IL-12-dependent pathway. J Immunol 158:5087-5090
42. 42. Oldstone MBA (1987) Molecular mimicry and autoimmune disease. Cell 50:819-820
43. 43. Davies JM (1997) Molecular mimicry: can epitope mimicry induce autoimmune disease? Immunol Cell Biol 75:113-126
44. 44. Wucherpfennig KW, Strominger JL (1995) Molecular mimicry in T cell-mediated autoimmunity: viral peptides activate human T cell clones specific for myelin basic protein. Cell 80:695-705
45. 45. Chicz RM, Urban RG, Gorga JC, Vignali DAA, Lane WS, Strominger JL (1993) Specificity and promiscuity among naturally processed peptides bound to HLA-DR alleles. J Exp Med 178:27-47
46. 46. Rammensee H-G, Friede T, Stevanovic S (1995) MHC ligands and peptide motifs: first listing. Immunogenetics 41:178-228
47. 47. Reay PA, Kantor RM, Davis MM (1994) Use of global amino acid replacements to define the requirements for MHC binding and T cell recognition of moth cytochrome c (93-103). J Immunol 152:3946-3957
48. 48. Hudrisier D, Mazarguil H, Laval F, Oldstone MBA, Gairin JE (1996) Binding of viral antigens to major histocompatibility complex class I H-2Db molecules is controlled by dominant negative elements at peptide non-anchor residues. Implications for peptide selection and presentation. J Biol Chem 271:17829-17836
49. 49. Garboczi DN, Ghosh P, Utz U, Fan QR, Biddison WE, Wiley DC (1996) Structure of the complex between human T-cell receptor, viral peptide and HLA-A2. Nature 384:134-141
50. 50. Garcia KC, Degano M, Stanfield RL, Brunmark A Jackson MR, Peterson PA, Teyton L, Wilson IA (1996) An αβ T cell receptor structure at 2.5 A and its orientation in the TCR-MHC complex. Science 274:209-219
51. 51. Ota K, Matsui M, Milford EL, Mackin GA, Weiner HL, Hafler D (1990) T-cell recognition of an immunodominant myelin basic protein epitope in multiple sclerosis. Nature 346:183-187
52. 52. Pette M, Fujita K, Wilkinson D, Altmann DM, Trowsdale J, Giegerich G, Hinkkanen A Epplen JT, Kappos L, Wekerle H (1990) Myelin autoreactivity in multiple sclerosis; recognition of myelin basic protein in the context of HLA-DR2 products by T lymphocytes of multiple sclerosis patients and healthy donors. Proc Natl Acad Sci USA 87:7968-7972
53. 53. Martin R, Jaraquemada D, Flerlage M, Richert J, Whitaker J, Long EO, McFarlin DE, McFarland HF (1990) Fine specificity and HLA restriction of myelin basic protein-specific cytotoxic T cell lines from multiple sclerosis patients and healthy individuals. J Immunol 145:540-548
54. 54. Wucherpfennig KW, Zhang J, Witek C, Matsui M, Modabber Y, Ota K, Hafler DA (1994) Clonal expansion and persistence of human T cells specific for an immunodominant myelin basic protein peptide. J Immunol 152:5581-5592
55. 55. Wucherpfennig KW, Sette A, Southwood S, Oseroff C, Matsui M, Strominger JL, Hafler DA (1994) Structural requirements for binding of an immunodominant myelin basic protein peptide to DR2 isotypes and for its recognition by human T cell clones. J Exp Med 179:279-290
56. 56. Wucherpfennig KW, Hafler DA, Strominger JL (1995) Structure of human T-cell receptors specific for an immunodominant myelin basic protein peptide: positioning of T-cell receptors on HLA-DR2/peptide complexes. Proc Natl Acad Sci USA 92:8896-8900
57. 57. Vergelli M, Hemmer B, Kalbus M, Vogt AB, Ling N, Conlon P, Coligan JE, McFarland H, Martin R (1997) Modifications of peptide ligands enhancing T cell responsiveness imply large numbers of stimulatory ligands for autoreactive T cells. J Immunol 158:3746-3752
58. 58. Ausubel LJ, Kwan CK, Sette A, Kuchroo V, Hafler DA (1996) Complementary mutations in an antigenic peptide allow for crossreactivity of autoreactive T-cell clones. Proc Natl Acad Sci USA 93:15317-15322
59. 59. Hemmer B, Fleckenstein BT, Vergelli M, Jung G, McFarland H, Martin R, Wiesmüller K-H (1997) Identification of high potency microbial and self ligands for a human autoreactive class II-Restricted T cell clone. J Exp Med 185:1651-1659
60. 60. McRae BL, Karandikar NJ, Miller SD (1997) Degenerate antigen recognition by effector CD4 + T cells in experimental autoimmune encephalomyelitis. J Neuroimmunol 75:156-162
61. 61. Inobe J-i, Yamamura T, Kunishita T, Tabira T (1993) T lymphocyte lines and clones selected against synthetic myelin basic protein 82-102 peptide from Japanese multiple sclerosis patients. J Neuroimmunol 46:83-90
62. 62. Warren KG, Catz I, Steinman L (1995) Fine specificity of the antibody response to myelin basic protein in the central nervous system in multiple sclerosis: the minimal B-cell epitope and a model of its features. Proc Natl Acad Sci USA 92:11061-11065
63. 63. Wucherpfennig KW, Catz I, Hausmann S, Strominger JL, Steinman L, Warren KG (1997) Recognition of the immunodominant myelin basic protein peptide by autoantibodies and HLA-DR2 restricted T-cell clones from multiple sclerosis patients: identity of key contact residues in the B-cell and T-cell epitopes. J Clin Invest 100:1114-1122
64. 64. Talbot PJ, Paquette J-S, Ciurli C, Antel JP, Quellet F (1996) Myelin basic protein and human coronavirus 229E cross-reactive T cells in multiple sclerosis. Ann Neurol 39:233-240
65. 65. Cohn ML, Robinson ED, Thomas D, Faerber M, Carey S, Sawyer R, Goswami KKA, Johnson AH, Richert JR (1996) T cell responses to the paramyxovirus simian virus 5: studies in multiple sclerosis and normal populations. Pathobiology 64:131-135
66. 66. Fujinami RS, Oldstone MBA (1985) Amino acid homology between the encephalitogenic site of myelin basic protein and virus: mechanism for autoimmunity. Science 230:1043-1045
67. 67. Gautam AM, Pearson CI, Smilek DE, Steinman L, McDevitt HO (1992) Apolyalanine peptide with only five native myelin basic protein residues induces autoimmune encephalomyelitis. J Exp Med 176:605-609
68. 68. Gautam AM, Lock CB, Smilek DE, Pearson CI, Steinman L, McDevitt HO (1994) Minimal structural requirements for peptide presentation by major histocompatibility complex class II molecules: implications in induction of autoimmunity. Proc Natl Acad Sci USA 91:767-771
69. 69. Singh VK, Nagaraju K (1996) Experimental autoimmune uveitis: molecular mimicry and oral tolerance. Immunol Res 15:323-346
70. 70. Garza KM, Tung KSK (1995) Frequency of molecular mimicry among T cell peptides as the basis for autoimmune disease and autoantibody induction. J Immunol 155:5444-5448
71. 71. van Eden W, Hogervorst EJM, Hensen EJ, van der Zee R, van Embden JDA, Cohen IR (1989) A cartilage-mimicking T-cell epitope on a 65K mycobacterial heat shock protein: adjuvant arthritis as a model for human rheumatoid arthritis. Curr Top Microbiol Immunol 145:27-43
72. 72. Moudgil KD, Chang TT, Eradat H, Chen AM, Gupta RS, Brahn E, Sercarz EE (1997) Diversification of T cell responses to carboxy-terminal determinants within the 65-kD heat-shock protein is involved in regulation of autoimmune arthritis. J Exp Med 185:1307-1316
73. 73. Huber SA, Cunningham MW (1996) Streptococcal M protein peptide with similarity to myosin induces CD4 + T cell-dependent myocarditis in MRL/+ + mice and induces partial tolerance against coxsackieviral myocarditis. J Immunol 156:3528-3534
74. 74. von Herrath MG, Evans CF, Horwitz MS, Oldstone MBA (1996) Using transgenic mouse models to dissect the pathogenesis of virus-induced autoimmune disorders of the islets of Langerhans and the central nervous system. Immunol Rev 152:111-143
75. 75. Ohashi PS, Oehen S, Buerki K, Pircher H, Ohashi CT, Odermatt B, Malissen B, Zinkernagel RM, Hengartner H (1991) Ablation of 'tolerance' and induction of diabetes by virus infection in viral antigen transgenic mice. Cell 65:305-317
76. 76. Oldstone MBA, Nerenberg M, Southern P, Price J, Lewicki H (1991) Virus infection triggers insulin-dependent diabetes mellitus in a transgenic model: role of anti-self (virus) immune response. Cell 65:319-331
77. 77. Evans CF, Horwitz MS, Hobbs MV, Oldstone MBA (1996) Viral infection of transgenic mice expressing a viral protein in oligodendrocytes leads to chronic central nervous system autoimmune disease. J Exp Med 184:2371-2384
78. 78. Kuchroo VK, Martin CA, Greer JM, Ju ST, Sobel RA, Dorf ME (1993) Cytokines and adhesion molecules contribute to the ability of myelin proteolipid protein-specific T cell clones to mediate experimental allergic encephalomyelitis. J Immunol 151:4371-4382
79. 79. Lafaille JJ, Keere FV, Hsu AL, Baron JL, Haas W, Raine CS, Tonegawa S (1997) Myelin basic protein-specific T helper (Th2) cells cause experimental autoimmune encephalomyelitis in immunodeficient hosts rather than protect them from the disease. J Exp Med 186:307-312
80. 80. Marrack P, Kappler J (1990) The staphylococcal enterotoxins and their relatives. Science 248:705-711
81. 81. Kotzin BL, Leung DY, Kappler J, Marrack P (1993) Superantigens and their potential role in human disease. Adv Immunol 54:99-166
82. 82. Kotzin BL (1995) Superantigens and their role in disease. Hosp Pract 29:59-70
83. 83. Renno T, Acha-Orbea H (1996) Superantigens in autoimmune diseases: still more shades of gray. Immunol Rev 154:175-191
84. 84. Acha-Orbea H, MacDonald HR (1995) Superantigens of the mouse mammary tumor virus. Annu Rev Immunol 13:459-486
85. 85. Held W, Acha-Orbea H, MacDonald HR, Waanders GA (1994) Superantigens and retroviral infection: insights from mouse mammary tumor virus. Immunol Today 15:184
86. 86. Bergdoll MS (1995) Importance of Staphylococci that produce nanogram quantities of enterotoxin. Intern J Med Microbiol 282:1-6
87. 87. Seth A, Stern LJ, Ottenhoff TH, Engel I, Owen MJ, Lamb JR, Klausner RD, Wiley DC (1994) Binary and ternary complexes between T-cell receptor, class II MHC and superantigen in vitro. Nature 369:324-327
88. 88. Swaminathan S, Furey W, Pletcher J, Sax M (1992) Crystal structure of staphylococcal enterotoxin B, a superantigen, Nature 359:801-806
89. 89. Kappler JW, Herman A, Clements J, Marrack P (1992) Mutations defining functional regions of the superantigen staphylococcal enterotoxin. Br J Exp Med 175:387-396
90. 90. Jardetzky TS, Brown JH, Gorga JC, Stern LJ, Urban RG, Chi YI, Stauffacher C, Strominger JL, Wiley DC (1994) Three-dimensional structure of a human class II histocompatibility molecule complexed with superantigen. Nature 368:711-718
91. 91. Kim J, Urban RG, Strominger JL, Wiley DC (1994) Toxic shock syndrome toxin-1 complexed with a class II major histocompatibility molecule HLA-DR1. Science 266:1870-1874
92. 92. Ulrich RG, Bavari S, Olson MA (1995) Staphylococcal enterotoxins A and B share a common structural motif for binding class II major histocompatibility complex molecules. Nature Struct Biol 2:554-560
93. 93. Johnson HM, Torres B, Soos JM (1996) Superantigens: structure and relevance to human disease. Proc Soc Exp Biol Med 212:99-109
94. 94. Schiffenbauer J, Johnson HM, Butfiloski EJ, Wegrzyn L, Soos JM (1993) Staphylococcal enterotoxins can re-activate experimental allergic encephalomyelitis. Proc Natl Acad Sci USA 90:8543-8546
95. 95. Brocke S, Gaur A, Piercy C, Gautam A, Gijbels K, Fathman CG, Steinman L (1993) Induction of relapsing paralysis in experimental autoimmune encephalomyelitis by bacterial superantigen. Nature 365:642-644
96. 96. Brocke S, Veromaa T, Weissman IL, Gijbels K, Steinman L (1994) Infection and multiple sclerosis: a possible role for superantigens? Trends Microbiol 2,7:250-254
97. 97. Soos JM, Hobeika AC, Butfiloski EJ, Schiffenbauer J, Johnson HM (1995) Accelerated induction of experimental allergic encephalomyelitis in PL/J mice by a non-V/38-specific superantigen. Proc Natl Acad Sci USA 92:6082-6086
98. 98. Soos JM, Subramaniam PS, Hobeika AC, Schiffenbauer J, Johnson HM (1995) The interferon pregnancy recognition hormone, IFN-tau, blocks both development and superantigen reactivation of experimental allergic encephalomyelitis without associated toxicity. J Immunol 155:2747-2753
99. 99. Gaur A, Fathman CG, Steinman L, Brocke S (1993) SEB induced anergy: modulation of immune response to T cell determinants of myoglobin and myelin basic protein. J Immunol 150:3062-3069
100. 100. Rott O, Mignon-Godefroy, Fleischer B, Charreire J, Cash E (1995) Superantigens induce primary T cell responses to soluble autoantigens by a non-Vβ-specific mechanism of bystander activation. Cell Immunol 161:158-165
101. 101. Rott O, Wekerle H, Fleischer B (1992) Protection from experimental allergic encephalomyelitis by application of a bacterial superantigen. Int Immunol 4:347-353
102. 102. Soos JM, Schiffenbauer J, Johnson HM (1993) Treatment of PL/J mice with the superantigen staphylococcal enterotoxin B prevents development of experimental allergic encephalomyelitis. J Neuroimmunol 43:39-43
103. 103. Kalman B, Lublin FD, Lattime E, Joseph J, Knobler RL (1993) Effects of staphylococcal enterotoxin B on T cell receptor V beta utilization and clinical manifestations of experimental allergic encephalomyelitis. J Neuroimmunol 45:83-88
104. 104. Kim C, Siminovitch KA, Ochi A (1991) Reduction of lupus nephritis in MRL/lpr mice by a bacterial superantigen treatment. J Exp Med 174:1431-1437
105. 105. Prabhu Das MR, Cohen A, Zamvil SS, Offner H, Kuchroo VK (1996) Prior exposure to superantigen can inhibit or exacerbate autoimmune encephalomyelitis: T-cell repertoire engaged by the autoantigen determines clinical outcome. J Neuroimmunol 71:3-10
106. 106. Crisi GM, Santambrogio L, Hochwald GM, Smith SR, Carlino JA, Thorbecke GJ (1995) Staphylococcal enterotoxin B and tumor-necrosis factor-α-induced relapses of experimental allergic encephalomyelitis: protection by transforming growth factor-β and interleukin-10. Eur J Immunol 25:3035-3040
107. 107. Stinissen P, Vandevyver C, Medaer R, Vandegaer L, Nies J, Tuyls L, Hafler DA, Raus J, Zhang J (1995) Increased frequency of T cells in cerebrospinal fluid and peripheral blood of patients with multiple sclerosis. Reactivity, cytotoxicity, and T cell receptor V gene rearrangements. J Immunol 154:4883-4894
108. 108. Conrad B, Weissmahr RN, Boni J, Arcari R, Schüpbach J, Mach B (1997) A human endogenous retroviral superantigen as candidate autoimmune gene in type I diabetes. Cell 90:303-313