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Bovine gallbladder mucin binds bilirubin in vitro
August
1983
EDITORIALS
5. Truelove SC, Witts LJ. Cortisone and corticotropin in ulcerative colitis. Br Med J 1959;1:387-94. 6. Kaplan HP, Portnoy P, Binder HJ, et al. A controlled evaluation of intravenous adrenocorticotropic hormone and hydrocortisone in the treatment of acute colitis. Gastroenterology 1975;69:91-5. 7. Powell-Tuck J, Buckell NA, Lennard-Jones JE. A controlled comparison of corticotropin and hydrocortisone in the treatment of severe proctocolitis. Stand J Gastroenterol 1977; 12:971-5. 8. Meyers S, Sachar DB, Goldberg JD, Janowitz HD. Corticotropin
475
versus hydrocortisone in the intravenous treatment of ulcerative colitis. A prospective, randomized, double-blind clinical trial. Gastroenterology 1983;85:351-7.
Address requests for reprints to: Mark A. Peppercorn, M.D., Beth Israel Hospital, Department of Medicine, 330 Brookline Avenue, Boston, Massachusetts 02215. 0 1983 by the American Gastroenterological Association
Infectious Agents and Inflammatory Bowel Disease The search for the etiology of inflammatory bowel disease (IBD) remains one of the most frustrating problems in the field of gastroenterology. Since multiple factors undoubtedly contribute to IBD, different approaches of investigation will be necessary to elucidate its etiology. One such approach has focused on infectious agents as the cause of IBD. Because of the problems of bacterial contamination and immunopathological responses confined to the gut, investigation in this area requires meticulousness and patience. These qualities are reflected in the article by Belsheim et al. (1) on the association between L forms and IBD reported in this issue of GASTROENTEROLOGY. L forms are cell wall-deficient variants of conventional bacteria. They are maintained in special hypertonic medium because of the absence of the protective cell wall and are capable of replication and reversion to the parental form. They were first reported to be associated with IBD in 1970 (2). Although L forms have been shown to induce granulomas in laboratory animals, the mechanism by which they might induce IBD in humans is speculative. Nevertheless, the article by Belsheim et al. confirms and extends the previously noted association between L forms and IBD. The article is noteworthy for several reasons. First, the study is well designed, utilizing a blinded, prospective protocol to examine intestinal biopsy specimens in two separate laboratories for the presence of L forms. Specimens from 189 subjects (71 Crohn’s disease and 121 ulcerative colitis) and 140 control specimens were studied, making this the largest study in this area in the literature. Second, the investigators circumvented the potential methodological problem of antibiotic-induced conversion
of bacteria to L forms in vitro by first filtering the homogenized specimens to remove conventional bacteria. As the authors point out, it is unlikely that filter rupture or leakage occurred selectively in the filters used for the IBD biopsy specimens and not the control specimens. Third, the statistically sound interpretation of the results confirms that bacterial L forms are recovered more frequently from Crohn’s disease (44%) and ulcerative colitis (54%) than control (1%) subjects. In addition, the authors observed that drug treatment in vivo did not alter L-form recovery. Thus, if L forms directly or indirectly cause IBD, the observation that drug therapy in vivo did not affect L-form recovery could explain the persistence of clinical disease despite numerous drug regimens. Also, the observation that L forms were recovered from IBD tissue and not from adjacent stool suggests that tissue factors participate in the localization of L forms. Similar to many provocative studies, the article by Belsheim et al. raises many additional questions. For example, if L forms cause IBD, why were they recovered from only half the IBD patients? In the IBD patients from whom they were not recovered, could disease be caused by L forms before or after their reversion to the parental form? However, since the parental form of the L forms isolated in the study were normal, nonpathogenic gut organisms, how might they cause disease? Also, why were L forms recovered from involved and uninvolved tissue? Finally, since many features of Crohn’s disease and ulcerative colitis indicate that they are two separate disease processes, the similar L-form types and recovery frequencies from subjects in each group are perplexing. With these questions in mind, Belsheim et al. deserve credit for raising the obvious possibili-
476
GASTROENTEROLOGY
EDITORIALS
ty: the presence of L forms in IBD may be secondary to local unknown factors created by the disease process. The initial enthusiasm for an infectious etiology for IBD was the result of animal transmission studies (2). In these studies, the inoculation of homogenized, human IBD tissue into laboratory animals produced granulomas which could then be passaged into other animals. Despite the inability of investigators in other laboratories to reproduce these results (3) and the finding of foreign material (hair and keratin) in many granulomas (4), attempts were made to isolate the putative agent, possibly a virus, using a variety of cell culture systems. The varying sensitivity and specificity of these systems, the problem of mycoplasma contamination (5), and the failure to include control tissue from patients with inflammatory diseases other than IBD again yielded insufficiently reproducible and often conflicting results (6,7). Recently, acid-fast materials suggesting mycobacteria (8) and coryneform organisms (9) were cultured from the mesenteric lymph nodes of IBD patients. On epidemiologic grounds, mycobacteria are an unlikely cause of IBD. Interestingly, Belsheim et al. did not find any L-form mycobacteria in their biopsy specimens. In addition, recent attempts to relate the etiology and the course of IBD to qualitative and/or quantitative changes in normal gut microflora are also insufficiently controlled or too preliminary to provide a basis on which to draw firm conclusions. Thus, the investigations into an infectious cause of IBD have been difficult to interpret because of inadequate controls, methodological problems, conflicting results, and the failure to isolate an organism that fulfills Koch’s postulates. In this regard, an animal model for testing the pathogenicity of infectious agents would help clarify whether the presence of an organism(s) causes IBD or is the consequence of a diseased intestine. Despite the above problems with many of the studies on infectious agents in IBD, exposure to one or more, perhaps still unidentified, gut microorganisms may be the etiologic common denominator in IBD. Acting in a manner analogous to the possibly viral-induced acquired immune-deficiency syndrome (AIDS) but confined to the gut, the microorganisms could act directly, or indirectly through gut antigen presenting cells, on a helper/inducer subset of intestinal T lymphocytes which in turn could act selectively through complex pathways on monocytes/macrophages and a second subset of T lymphocytes. Through soluble signals (monokines and lymphokines) these cells could promote inflammation, antigen-specific granuloma formation, and accelerated fibroblast activity (10-12). Antigen leakage across the mucosal barrier or the recirculation of local cellular immune components could induce the
Vol.
85, No. 2
systemic autoimmune features observed in some IBD patients. Genetic predisposition and/or restriction could influence the response at any of the steps of antigen-cell or cell-cell interaction. That the microorganisms and immune responses largely are confined to the gut makes this a more difficult and consequently more challenging disease process to investigate and understand. PHILLIP
D. SMITH,
M.D.
Laboratory of Microbiology and Immunology National Institute of Dental Research National Institutes of Health Bethesda, Maryland
References 1. Belsheim
MR, Darwish
RZ, Watson
WC, Schieven
B. Bacterial
L-form isolation from inflammatory bowel disease patients. Gastroenterology 1983;85:364-9. 2. Mitchell DN, Rees BJW. Agent transmissible from Crohn’s disease tissue. Lancet 197O;ii:168-71. 3. Bolton PM, Owen E, Heatley RV, Jones Williams W, Hughes LE. Negative findings in laboratory animals for a transmissible agent in Crohn’s disease. Lancet 1973;ii:1122-4. 4. Cohen Z, Leung MK, Jirsch D, Archibald S, Cullen J, Gardner J. Transmission of IBD homogenates in inbred mice and rabbits. In: Pena AS, Weterman IT, Booth CC, Strober W, eds. Proceedings of the Second International Workshop on Crohn’s Disease. The Hague: Martinus Nijhoff Publishers, 1981:259-65. 5. Kapikian AZ, Barile MF, Wyatt RF, et al. Mycoplasma contamination in cell culture of Crohn’s disease material. Lancet 1979;ii:466-7. 6. Aronson MD, Phillips CA, Beeken WL, Forsyth BR. Isolation and characterization of a viral agent from intestinal tissue of patients with Crohn’s disease and other intestinal disorders. Progr Med Virol 1975;21:165-76. 7. Phillpotts RJ, Hermon-Taylor J, Brooke BN. Virus isolation studies in Crohn’s disease: a negative report. Gut 1979; 20:1057-62. 8. Burnham WR, Lennard-Jones JE, Stanford JL, Bird RG. Mycobacterium as a possible cause of inflammatory bowel disease. Lancet 1978;ii:693-6. 9 White S. Investigation into the identity of acid fast organisms isolated from Crohn’s disease and ulcerative colitis. In: Pena AS, Waterman IT, Booth CC, Strober W, eds. Proceedings of the Second International Workshop on Crohn’s Disease. The Hague: Martinus Nijhoff Publishers, 1981:278-82. 10 Ginsburg CH, McCluskey RT, Nepom JT, et al. Antigenand receptor-driven regulatory mechanisms. X. The induction and suppression of hapten-specific granuloma. Am J Path01 1982;106:421-31. 11 Wyler DJ, Wahl SM, Wahl LM. Hepatic fibrosis in schistosomiasis: egg granulomas secrete fibroblast stimulating factor in vitro. Science 1978;202:438-40. 12 Wahl SM. Immunologically induced fibrosis. In: Fleishmajer R, ed. Progress in disease of the skin. New York: Grune & Stratton, 1983 (in press).
Address requests for reprints to: Phillip D. Smith, M.D., Building 30, Room 322, National Institutes of Health, Bethesda, Maryland 20205. 0 1983 by the American Gastroenterological Association
1983
EDITORIALS
5. Truelove SC, Witts LJ. Cortisone and corticotropin in ulcerative colitis. Br Med J 1959;1:387-94. 6. Kaplan HP, Portnoy P, Binder HJ, et al. A controlled evaluation of intravenous adrenocorticotropic hormone and hydrocortisone in the treatment of acute colitis. Gastroenterology 1975;69:91-5. 7. Powell-Tuck J, Buckell NA, Lennard-Jones JE. A controlled comparison of corticotropin and hydrocortisone in the treatment of severe proctocolitis. Stand J Gastroenterol 1977; 12:971-5. 8. Meyers S, Sachar DB, Goldberg JD, Janowitz HD. Corticotropin
475
versus hydrocortisone in the intravenous treatment of ulcerative colitis. A prospective, randomized, double-blind clinical trial. Gastroenterology 1983;85:351-7.
Address requests for reprints to: Mark A. Peppercorn, M.D., Beth Israel Hospital, Department of Medicine, 330 Brookline Avenue, Boston, Massachusetts 02215. 0 1983 by the American Gastroenterological Association
Infectious Agents and Inflammatory Bowel Disease The search for the etiology of inflammatory bowel disease (IBD) remains one of the most frustrating problems in the field of gastroenterology. Since multiple factors undoubtedly contribute to IBD, different approaches of investigation will be necessary to elucidate its etiology. One such approach has focused on infectious agents as the cause of IBD. Because of the problems of bacterial contamination and immunopathological responses confined to the gut, investigation in this area requires meticulousness and patience. These qualities are reflected in the article by Belsheim et al. (1) on the association between L forms and IBD reported in this issue of GASTROENTEROLOGY. L forms are cell wall-deficient variants of conventional bacteria. They are maintained in special hypertonic medium because of the absence of the protective cell wall and are capable of replication and reversion to the parental form. They were first reported to be associated with IBD in 1970 (2). Although L forms have been shown to induce granulomas in laboratory animals, the mechanism by which they might induce IBD in humans is speculative. Nevertheless, the article by Belsheim et al. confirms and extends the previously noted association between L forms and IBD. The article is noteworthy for several reasons. First, the study is well designed, utilizing a blinded, prospective protocol to examine intestinal biopsy specimens in two separate laboratories for the presence of L forms. Specimens from 189 subjects (71 Crohn’s disease and 121 ulcerative colitis) and 140 control specimens were studied, making this the largest study in this area in the literature. Second, the investigators circumvented the potential methodological problem of antibiotic-induced conversion
of bacteria to L forms in vitro by first filtering the homogenized specimens to remove conventional bacteria. As the authors point out, it is unlikely that filter rupture or leakage occurred selectively in the filters used for the IBD biopsy specimens and not the control specimens. Third, the statistically sound interpretation of the results confirms that bacterial L forms are recovered more frequently from Crohn’s disease (44%) and ulcerative colitis (54%) than control (1%) subjects. In addition, the authors observed that drug treatment in vivo did not alter L-form recovery. Thus, if L forms directly or indirectly cause IBD, the observation that drug therapy in vivo did not affect L-form recovery could explain the persistence of clinical disease despite numerous drug regimens. Also, the observation that L forms were recovered from IBD tissue and not from adjacent stool suggests that tissue factors participate in the localization of L forms. Similar to many provocative studies, the article by Belsheim et al. raises many additional questions. For example, if L forms cause IBD, why were they recovered from only half the IBD patients? In the IBD patients from whom they were not recovered, could disease be caused by L forms before or after their reversion to the parental form? However, since the parental form of the L forms isolated in the study were normal, nonpathogenic gut organisms, how might they cause disease? Also, why were L forms recovered from involved and uninvolved tissue? Finally, since many features of Crohn’s disease and ulcerative colitis indicate that they are two separate disease processes, the similar L-form types and recovery frequencies from subjects in each group are perplexing. With these questions in mind, Belsheim et al. deserve credit for raising the obvious possibili-
476
GASTROENTEROLOGY
EDITORIALS
ty: the presence of L forms in IBD may be secondary to local unknown factors created by the disease process. The initial enthusiasm for an infectious etiology for IBD was the result of animal transmission studies (2). In these studies, the inoculation of homogenized, human IBD tissue into laboratory animals produced granulomas which could then be passaged into other animals. Despite the inability of investigators in other laboratories to reproduce these results (3) and the finding of foreign material (hair and keratin) in many granulomas (4), attempts were made to isolate the putative agent, possibly a virus, using a variety of cell culture systems. The varying sensitivity and specificity of these systems, the problem of mycoplasma contamination (5), and the failure to include control tissue from patients with inflammatory diseases other than IBD again yielded insufficiently reproducible and often conflicting results (6,7). Recently, acid-fast materials suggesting mycobacteria (8) and coryneform organisms (9) were cultured from the mesenteric lymph nodes of IBD patients. On epidemiologic grounds, mycobacteria are an unlikely cause of IBD. Interestingly, Belsheim et al. did not find any L-form mycobacteria in their biopsy specimens. In addition, recent attempts to relate the etiology and the course of IBD to qualitative and/or quantitative changes in normal gut microflora are also insufficiently controlled or too preliminary to provide a basis on which to draw firm conclusions. Thus, the investigations into an infectious cause of IBD have been difficult to interpret because of inadequate controls, methodological problems, conflicting results, and the failure to isolate an organism that fulfills Koch’s postulates. In this regard, an animal model for testing the pathogenicity of infectious agents would help clarify whether the presence of an organism(s) causes IBD or is the consequence of a diseased intestine. Despite the above problems with many of the studies on infectious agents in IBD, exposure to one or more, perhaps still unidentified, gut microorganisms may be the etiologic common denominator in IBD. Acting in a manner analogous to the possibly viral-induced acquired immune-deficiency syndrome (AIDS) but confined to the gut, the microorganisms could act directly, or indirectly through gut antigen presenting cells, on a helper/inducer subset of intestinal T lymphocytes which in turn could act selectively through complex pathways on monocytes/macrophages and a second subset of T lymphocytes. Through soluble signals (monokines and lymphokines) these cells could promote inflammation, antigen-specific granuloma formation, and accelerated fibroblast activity (10-12). Antigen leakage across the mucosal barrier or the recirculation of local cellular immune components could induce the
Vol.
85, No. 2
systemic autoimmune features observed in some IBD patients. Genetic predisposition and/or restriction could influence the response at any of the steps of antigen-cell or cell-cell interaction. That the microorganisms and immune responses largely are confined to the gut makes this a more difficult and consequently more challenging disease process to investigate and understand. PHILLIP
D. SMITH,
M.D.
Laboratory of Microbiology and Immunology National Institute of Dental Research National Institutes of Health Bethesda, Maryland
References 1. Belsheim
MR, Darwish
RZ, Watson
WC, Schieven
B. Bacterial
L-form isolation from inflammatory bowel disease patients. Gastroenterology 1983;85:364-9. 2. Mitchell DN, Rees BJW. Agent transmissible from Crohn’s disease tissue. Lancet 197O;ii:168-71. 3. Bolton PM, Owen E, Heatley RV, Jones Williams W, Hughes LE. Negative findings in laboratory animals for a transmissible agent in Crohn’s disease. Lancet 1973;ii:1122-4. 4. Cohen Z, Leung MK, Jirsch D, Archibald S, Cullen J, Gardner J. Transmission of IBD homogenates in inbred mice and rabbits. In: Pena AS, Weterman IT, Booth CC, Strober W, eds. Proceedings of the Second International Workshop on Crohn’s Disease. The Hague: Martinus Nijhoff Publishers, 1981:259-65. 5. Kapikian AZ, Barile MF, Wyatt RF, et al. Mycoplasma contamination in cell culture of Crohn’s disease material. Lancet 1979;ii:466-7. 6. Aronson MD, Phillips CA, Beeken WL, Forsyth BR. Isolation and characterization of a viral agent from intestinal tissue of patients with Crohn’s disease and other intestinal disorders. Progr Med Virol 1975;21:165-76. 7. Phillpotts RJ, Hermon-Taylor J, Brooke BN. Virus isolation studies in Crohn’s disease: a negative report. Gut 1979; 20:1057-62. 8. Burnham WR, Lennard-Jones JE, Stanford JL, Bird RG. Mycobacterium as a possible cause of inflammatory bowel disease. Lancet 1978;ii:693-6. 9 White S. Investigation into the identity of acid fast organisms isolated from Crohn’s disease and ulcerative colitis. In: Pena AS, Waterman IT, Booth CC, Strober W, eds. Proceedings of the Second International Workshop on Crohn’s Disease. The Hague: Martinus Nijhoff Publishers, 1981:278-82. 10 Ginsburg CH, McCluskey RT, Nepom JT, et al. Antigenand receptor-driven regulatory mechanisms. X. The induction and suppression of hapten-specific granuloma. Am J Path01 1982;106:421-31. 11 Wyler DJ, Wahl SM, Wahl LM. Hepatic fibrosis in schistosomiasis: egg granulomas secrete fibroblast stimulating factor in vitro. Science 1978;202:438-40. 12 Wahl SM. Immunologically induced fibrosis. In: Fleishmajer R, ed. Progress in disease of the skin. New York: Grune & Stratton, 1983 (in press).
Address requests for reprints to: Phillip D. Smith, M.D., Building 30, Room 322, National Institutes of Health, Bethesda, Maryland 20205. 0 1983 by the American Gastroenterological Association