List of Contributors Mahmoud Abu-Shakra Bradford C. Braden Rheumatic Diseases Unit Center for Advanced Research in Biotechnology Ben-Gurion University and Soroka Medical Centre University of Maryland Biotechnology Institute Beer-Sheva, Israel Rockville, MD 20850, USA Howard Amital Bernard R. Brodeur Department of Medicine 'B' Unite de Recherche en Vaccinologie Research Unit of Autoimmune Diseases Centre de Recherche du Centre Hospitaller de Chaim Sheba Medical Center rUniversite Laval Tel-Hashomer Sainte-Foy, Quebec, Canada and Sackler Faculty of Medicine Tel-Aviv University Dan Buskila Tel-Aviv, Israel Rheumatic Diseases Unit Ben-Gurion University and Soroka Medical Centre Beer-Sheva, Israel Ronit Bakimer Department of Immunology Michele Carbone Weizmann Institute of Sciences Department of Pathology Rehovot, 76100, Israel University of Chicago Chicago, IL 60637, USA Nenad Ban Department of Biochemistry Antonio Cassone University of California Laboratorio di Batteriologia e Micologia Medica Riverside, CA 92521, USA Istituto Superiore di Sanita Rome, Italy Agostino Bazzichi Department of Biomedicine Paul B. Chapman University of Pisa Melanoma Section 1-56127 Pisa, Italy Clinical Immunology Service Department of Medicine Andrea Benden Memorial Sloan-Kettering Cancer Center The Wistar Institute New York, NY 10021, USA Philadelphia, PA 19104, USA S. Conti F. De Bernardis Istituto di Microbiologia Laboratorio di Batteriologia e Micologia Medica Universita di Parma Istituto Superiore di Sanita Parma, Italy Rome, Italy Elena Csernok Malaya Bhattacharya-Chatterjee Department of Rheumatology Markey Cancer Center University of Liibeck University of Kentucky Rheumaklinik Bad Bramstedt Lexington, KY 40536-0093, USA BadBramstedt, 24576, Germany Constantin A. Bona Lilia Dakovska Department of Microbiology Clinical Center of Endocrinology and Mount Sinai School of Medicine Gerontology Medical Faculty New York, NY 10029-6574, USA Sofia, Bulgaria Vll Franco Dammacco Franz-Josef Gaida Department of Biomedical Sciences and Department of Clinical Chemistry Human Oncology (D.I.MO) Medical Clinic Section of Internal Medicine University Hospital Eppendorf University of Bari Medical School D-20246 Hamburg, Germany Bari, Italy Carlo Garzelli Howard Dang Department of Biomedicine Audie L. Murphy Memorial Veterans Hospital University of Pisa San Antonio, TX 7874, USA 1-56127 Pisa, Italy YaronBarDayan M. Gerloni Department of Medicine 'B' Istituto di Microbiologia Research Unit of Autoimmune Diseases Universita di Parma Chaim Sheba Medical Center Parma, Italy Tel-Hashomer M. Eric Gershwin and Sackler Faculty of Medicine Division of Rheumatology, Allergy and Clinical Tel-Aviv University Immunology Tel-Aviv, Israel University of California at Davis TB 192, School of Medicine Smruti Desai Davis, CA 95616, USA Department of Microbiology and Immunology New York Medical College Michael Grant Valhalla, NY 10595, USA Immunology Program Faculty of Medicine Hildegund C. J. Ertl University of Newfoundland The Wistar Institute St. John's, Newfoundland, Canada Philadelphia, PA 19104, USA Neil S. Greenspan Giuseppe Falcone Department of Biological Science Department of Biomedicine Florida State University University of Pisa Tallahassee, FL 32308-3050, USA 1-56127 Pisa, Italy and Institute of Pathology Jan Fagerberg Case Western Reserve University Department of Oncology (Radiumhemmet) Cleveland, OH 44106-4943, USA Karolinska Hospital S-171 76 Stockhohn, Sweden Wolfgang L. Gross Department of Rheumatology Soldano Ferrone University of Liibeck Department of Microbiology and Immunology Rheumaklinik Bad Bramstedt New York Medical College Bad Bramstedt, 24576, Germany Valhalla, NY 10595, USA Josee Hamel Pnina Fishman Unite de Recherche en Vaccinologie Felsenshtein Research Institute Centre de Recherche du Centre Hospitaller de Beilinson Medical Campus rUniversite Laval Petach Tiqvah, Israel Sainte-Foy, Quebec, Canada Kenneth A. Foon Markey Cancer Center David Harris University of Kentucky Lankenau Hospital Lexington, KY 40536-0093, USA Wynnewood, PA 19096, USA vni Dorothee Herlyn Ivan Kehayov The Wistar Institute Department of Molecular Immunology Philadelphia, PA 19104, USA Institute of Biology and Immunology of Reproduction Bulgarian Academy of Sciences Jorma Hinkula Sofia, Bulgaria Microbiology and Tumorbiology Center Karolinska Institute and Department of Virology Ronald C. Kennedy Swedish Institute for Infectious Disease Control Department of Microbiology and Immunology 105 21 Stockholm, Sweden The University of Oklahoma Health Sciences Center Marina Incaprera Oklahoma City, OK 73190, USA Department of Biomedicine Heinz Kohler University of Pisa 1-56127 Pisa, Italy Markey Cancer Center University of Kentucky Lexington, KY 40536-0093, USA Franco Indiveri Department of Internal Medicine (DI.M.I) Dieter Krebs University of Genoa Medical School Department of Gynecology and Obstetrics Genoa, Italy University of Bonn Bonn, Germany Lutz Jacob The Wistar Institute Thomas J. Kunicki Philadelphia, PA 19104, USA Roon Research Center for Arteriosclerosis and Thrombosis Division of Experimental Thrombosis and Marc G. Jacquemin Hemostasis Katholieke Universiteit Leuven Department of Molecular and Experimental Center for Molecular and Vascular Biology Medicine and the Department of Vascular Campus Gasthuisberg, O & N Biology B-3000 Leuven, Belgium Scripps Research Institute La Jolla,CA 92037, USA Simon Karpatkin Department of Medicine Stanimir Kyurkchiev New York University Medical School Department of Molecular Immunology New York, NY 10016, USA Institute of Biology and Immunology of Reproduction Saoussen Karray Bulgarian Academy of Sciences Departement d'lmmunologie Sofia, Bulgaria Institut Pasteur 75015 Paris, France Ann Kari Lefvert Immunological Research Laboratory and Department of Medicine Srini Kaveri Karolinska Hospital, Karolinska Institute INSERM U430 and Universite Pierre et Marie Curie S-171 76 Stockholm, Sweden Hopital Broussais Paris, France Patrick S.C. Leung Division of Rheumatology, Allergy and Michel D. Kazatchkine Clinical Immunology INSERM U430 and Universite Pierre et Marie Curie University of California at Davis Hopital Broussais TB 192, School of Medicine Paris, France Davis, CA 95616, USA IX Michael Levi Abraham Mittelman Microbiology and Tumorbiology Center Department of Medicine Karolinska Institute and Department of Virology New York Medical College Swedish Institute for Infectious Disease Control Valhalla, NY 10595, USA 105 21 Stockholm, Sweden Marc Monestier Weiping Li Department of Microbiology and Immunology The Wistar Institute Temple University School of Medicine Philadelphia, PA 19104, USA Philadelphia, PA 19140, USA Min Lin Virology Section Sasha P. Moyes Animal Diseases Research Institute Kennedy Institute of Rheumatology Agriculture and Agri-Food Canada Hammersmith, London W6 7DW, UK Nepean, Ontario K2H 8P9, Canada Sybille Miiller Alexander H. Lucas Markey Cancer Center Children's Hospital Oakland Research Institute Department of Medicine Oakland, CA 94611, USA University of Kentucky Lexington, KY, USA Rizgar A. Mageed Kennedy Institute of Rheumatology Hammersmith, London W6 7DW, UK M.A. Nardi Department of Medicine Vanya Manolova New York University Medical School Department of Molecular Immunology New York, NY 10016, USA Institute of Biology and Immunology of Reproduction Jacob B. Natvig Bulgarian Academy of Sciences Institute of Immunology and Rheumatology Sofia, Bulgaria The National Hospital 0172 Oslo, Norway Haruhiko Maruyama The Wistar Institute Michael Neumaier Philadelphia, PA 19104, USA Department of Clinical Chemistry Michael Mastrangelo Medical Clinic, University Hospital Eppendorf Jefferson Medical College D-20246 Hamburg, Germany Philadelphia, PA 19107, USA Alfred Nisonoff Alexander McPherson Department of Biology Department of Biochemistry Rosenstiel Research Center University of California Brandeis University Riverside, CA 92521, USA Waltham, MA 02254-9110, USA HakanMellstedt Department of Oncology (Radiumhemmet) ElvyraJ.Noronha Karolinska Hospital Department of Microbiology and Immunology S-171 76 Stockholm, Sweden New York Medical College Valhalla, NY 10595, USA Ofer Merimsky Department of Oncology Diane J. Nugent Ichilov Hospital Children's Hospital of Orange County Tel-Aviv 64239, Israel Orange, CA 92668, USA Egbert Oosterwijk Jean-Marie R. Saint-Remy 814 Urological Research Laboratory Katholieke Universiteit Leuven Department of Urology Center for Molecular and Vascular Biology Academic Hospital Nijmegen Campus Gasthuisberg, O & N 6500 HB Nijmegen, The Netherlands B-3000 Leuven, Belgium Harald Schlebusch Harvey I. Pass Department of Gynecology and Obstetrics Thoracic Oncology Section University of Bonn Surgery Branch, NCI/NIH Bonn, Germany Bethesda, MD 20892, USA Jan Schmolling Federico Perosa Department of Gynecology and Obstetrics Department of Biomedical Sciences and University of Bonn Human Oncology (D.I.MO) Bonn, Germany Section of Internal Medicine John R. Schreiber University of Bari Medical School Department of Pediatrics Bari, Italy Case Western Reserve University School of Medicine Chief, Division of Infectious Diseases Dagmar Pieper Rainbow Babies and Childrens Hospital Department of Clinical Chemistry Cleveland, OH 44106, USA Medical Clinic, University Hospital Eppendorf D-20246 Hamburg, Germany Marco Scudeletti Department of Internal Medicine (DI.M.I) Roberto J. Poljak University of Genoa Medical School Center for Advanced Research in Biotechnology Genoa, Italy University of Maryland Biotechnology Institute Michael H. Shearer Rockville, MD 20850, USA Department of Microbiology and Immunology The University of Oklahoma Health Sciences Center L. Polonelli Oklahoma City, OK 73190, USA Istituto di Microbiologia Universita di Parma Mark A. Sherman Parma, Italy Division of Immunology and Department of Molecular Graphics Peter Ragnhammar Beckman Research Institute Department of Oncology (Radiumhemmet) City of Hope National Cancer Center Karolinska Hospital Duarte,CA91010,USA S-171 76 Stockholm, Sweden John E. Shively Division of Immunology and Jochen Reinsberg Department of Molecular Graphics Department of Gynecology and Obstetrics Beckman Research Institute University of Bonn City of Hope National Cancer Center Bonn, Germany Duarte,CA 91010, USA Kenneth H. Roux Yehuda Shoenfeld Department of Biological Science Department of Medicine 'B' Florida State University Research Unit of Autoimmune Diseases Tallahassee, FL 32308-3050, USA Chaim Sheba Medical Center and Tel-Hashomer Institute of Pathology and Sackler Faculty of Medicine Case Western Reserve University Tel-Aviv University Cleveland, OH 44106-4943, USA Tel-Aviv, Israel XI Rajasekharan Somasundaram H. Uemura The Wistar Institute Department of Urology Philadelphia, PA 19104, USA Nara University Nara, Japan Sergio H. Spalter Department of Immunology Uwe Wagner Institute of Biomedical Sciences Department of Gynecology and Obstetrics Sao Paulo, Brasil University of Bonn Bonn, Germany Maria Stamenova Department of Molecular Immunology Institute of Biology and Immunology of BrittaWahren Reproduction Microbiology and Tumorbiology Center Bulgarian Academy of Sciences Karolinska Institute and Department of Virology Sofia, Bulgaria Swedish Institute for Infectious Disease Control 105 21 Stockholm, Sweden Eilleen S. Tackaberry Life Sciences Division Xinhui Wang Bureau of Drug Research Department of Microbiology and Immunology Health Canada New York Medical College Ottawa, Ontario, Canada Valhalla, NY 10595, USA Norman Talal Department of Medicine Ronald E.Ward Division of Clinical Immunology Department of Molecular Immunology University of Texas Health Science Center Roswell Park Cancer Institute San Antonio, TX 78284-7874, USA Buffalo, NY 14263, USA Yasmin Thanavala Pierre Youinou Department of Molecular Immunology Laboratory of Immunology Roswell Park Cancer Institute Brest University Medical School Buffalo, NY 14263, USA Brest, France Keith M. Thompson Institute of Immunology and Rheumatology Jan Zaloudik The National Hospital The Wistar Institute 0172 Oslo, Norway Philadelphia, PA 19104, USA Yaron Tomer En-Min Zhou Division of Endocrinology and Metabolism Virology Section Department of Medicine Animal Diseases Research Institute Mount Sinai School of Medicine Agriculture and Agri-Food Canada New York, NY 10029, USA Nepean, Ontario K2H 8P9, Canada VasilkaTsvetkova Department of Molecular Immunology MoncefZouali Institute of Biology and Immunology of Reproduc Departement d'lmmunologie tion Bulgarian Academy of Sciences Institut Pasteur Sofia, Bulgaria 75015 Paris, France xn ©1997 Elsevier Science B.V. All rights reserved. Idiotypes in Medicine: Autoimmunity, Infection and Cancer Y. Shoenfeld, R.C. Kennedy and S. Ferrone, editors. ANTI-IDIOTYPES AS VACCINES: THEORETICAL CONSIDERATIONS Alfred Nisonoff Department of Biology, Rosenstiel Research Center, Brandeis University, Waltham, MA 02254-9110, USA The intention of this brief introductory chapter is to definition of idiotype are discussed in more detail provide historical background on idiotypy and to discuss elsewhere (Nisonoff, 1995). some of the issues involved in the use of anti-idiotypic As pointed out by Arthur Silverstein (1975), the (anti-Id) antibodies as surrogate antigens, and in par concept of idiotypy dates back to the turn of the cen ticular as vaccines. Various aspects of idiotypy have tury, when Paul Ehrlich and others predicted that anti been reviewed elsewhere (Bona and Moran, 1985; bodies might be directed against the combining regions Nisonoff, 1991; Greenspan, 1992; Kearney, 1993 of other antibodies (Himmelweit, 1956). At the time, Shoenfeld et al., 1994; Thanavala and Pride, 1994 of course, nothing was known about the molecular Kohler et al., 1995). The paper by Thanavala and Pride properties of an antibody. Ehrlich used the vague term (1994) includes a list of over 50 investigations in which "side chain" to express the notion that particular chemi anti-Id antibodies have been used to induce antibod cal structures define the antibody combining site and ies against bacteria, viruses, parasites and tumor an that differences in side chains could account for dif tigens. ferences in specificity. In addition to predicting that The property of expressing an idiotype applies to the combining regions of two antibodies could inter antibodies and T-cell receptors; for simplicity the act with one another, Ehrlich visualized the possibility present discussion will be confined to antibodies. that the side chains of an anti-antibody (anti-anti-X) Idiotypy has as its basis the diversity of antibodies, might resemble in structure the antigen (X), thus an which is so great that an epitope present on an anti ticipating Jeme's later formulation of an "internal body may be represented at very low frequency or be image" (see below). These early speculations seem undetectable serologically in pooled normal im particularly remarkable since they were made in the munoglobulins or antibodies of other specificities absence of information as to the actual structures within the same species. Such an epitope is called involved. an idiotope; the idiotype is the collection of idiotopes The modem era of research on idiotypy began in on an antibody molecule. Antibodies reactive with 1955 with the work of Kunkel and his collaborators idiotopes may remain in solution after thorough ad on human myeloma proteins (Slater et al., 1955). They sorption of an anti-Id antiserum with nonspecific demonstrated that individual myeloma proteins possess immunoglobulins. For reasons that are now obvious, antigenic determinants that could not be detected on idiotopes are associated, entirely or in part, with the other such proteins or normal serum Ig. Idiotypy in hypervariable regions of an antibody, discovered by antibodies was reported by Oudin and Michel (1963), Wu and Kabat (1970). Although hypervariable re who were working with rabbit antisalmonella antibod gions probably contribute to most or all idiotopes, ies, and by Kunkel's group in human antibodies to A an idiotope may also include amino acids present in substance (Kunkel et al., 1963). The term "idiotype", a framework region. Anti-idiotopes that bear a struc introduced by Oudin and Michel, was initially reserved tural resemblance to the original, external antigen for determinants identified by a homologous antiserum (see below) constitute only a small proportion of the (rabbit anti-rabbit in this instance). The term "indi anti-Id antibody population. Issues relating to the vidual antigenic specificity" was used by Kunkel and his collaborators, whose initial studies were carried identified, may become a useful tool and provide the out with rabbit antihuman antibodies. The distinction basis for numerous publications (e.g., the phospho- eventually disappeared from the literature and the term choline antigen in BALB/c mice). "idiotype" is now used irrespective of the source of the antiserum. Applications of CRIs For a time it was thought that idiotypes were unique to an individual animal as well as to antibodies of a Applications of CRIs include the following: given specificity. Exceptions were observed starting An idiotype provides a phenotypic marker for the in the late 1960s. Cold agglutinins from different in expression of particular V genes. For example, an early dividuals were found to share idiotopes, although gen demonstration of the linkage of genes encoding idio erally not complete idiotypes (Williams et al., 1968); type and heavy chain allotype indicated, in turn, the different mice of the B ALB/c strain were found to pro linkage of VH and CH genes (Blomberg et al., 1972; duce antibodies to pneumococcal C-carbohydrate that Pawlaketal., 1973). expressed the same idiotype (Cohn et al., 1969); shared The presence in an individual patient of myeloma idiotype in antibodies to streptococcal carbohydrates proteins of the IgM and IgG classes that shared idiotype was noted in some members of a partially inbred fam provided early evidence that class switching can occur ily of rabbits (Eichmann and Kindt, 1971); all indi while maintaining expression of the same VH gene vidual A/J mice were found to produce antibodies to (Wang et al., 1970). This had been inferred earlier the p-azobenzenearsonate hapten that shared idiotype through a demonstration of shared VH allotype in (Kuettner et al., 1972). In the case of induced anti rabbit IgG and IgM (Todd and Inman, 1967). Identity bodies shared idiotypy occurred in some but not all of of partial amino acid sequences of VH and VL regions the relevant antibody population. of the IgG and IgM myeloma proteins that shared Such recurrent or cross-reactive idiotypes (CRIs) idiotype provided convincing evidence for the reality are now known to be fairly prevalent in inbred strains of the proposed class switching mechanism (Wang et of mice and have proven useful in a variety of stud al, 1973). ies (see below). In general, antibodies encoding CRIs Many studies of somatic mutations, and the rela are encoded by germline genes that require few or tionship of specific mutations to affinity maturation no somatic mutations to allow expression of the in antibodies have made use of CRIs; one can read idiotype. A probable additional requirement is that ily screen for monoclonal antibodies expressing the antibodies expressing the idiotype have a sufficiently CRI by serological analysis and thereby obtain a high affinity so that receptors on B cells expressing collection of similar but nonidentical antibodies the idiotype can compete successfully with other re belonging to the same genetic family. From their ceptors specific for the same antigen but differing in sequences one can draw conclusions concerning the idiotype. This combination — expression in the germ sequential accumulation of mutations that have taken line and an affinity high enough to be competitive - place and their effects on affinity and on the ex can explain the recurrence of an idiotype within an pression of particular idiotopes that comprise the inbred strain, as well as intrastrain differences. (An idiotype. tibodies to a given antigen may be associated with a In collaboration with the laboratory of Erik Seising CRI in one strain but not another.) Despite the asso (Durdik et al., 1989) we used CRI expression as a ciation with germ line genes antibodies expressing clonal marker to provide serological evidence for a CRI exhibit heterogeneity (e.g., Lamoyi et al., interchromosomal H chain isotype switching in a 1980). Somatic mutations may result in a substan transgenic mouse. CRIs have also been used as clonal tial increase in affinity while preserving some (usu markers for studies of B cell development and the fate ally not all) of the idiotopes that comprise the idiotype of clones of B cells. (Sharon, 1990). The term CRI should thus be con The existence of CRIs facilitated the demonstra sidered as describing an idiotype family rather than tion that pretreatment with anti-Id antibodies can sup an idiotype. press the subsequent appearance of the idiotype in Whether a particular idiotype is cross-reactive response to challenge with the relevant antigen in vivo within an inbred strain depends on the antigen and the (Hart et al, 1972; Strayer et al., 1975) or in vitro strain. The actual prevalence of CRIs may be much (Cosenza and Kohler, 1972). A single anti-Id reagent lower than the popular perception because a CRI, once can be used for experiments on suppression with vari- ous members of an inbred strain. The suppression of 2. Interaction of the Anti-Id with Cellular Receptors idiotype by anti-Id provided one of the foundations (Other than Antibodies) for the External Antigen for Niels Jeme's idiotype network theory of immune regulation (Jeme, 1974). There have been numerous reports of the interaction of anti-Ids with cellular receptors for a variety of ex ternal antigens (reviewed in Gaulton and Greene, ANTI-ID ANTIBODIES EXPRESSING AN IN 1986). The earliest example was the work of Sege and TERNAL IMAGE OF THE ANTIGEN Peterson (1978), who showed that anti-anti-insulin antibodies could bind to insulin receptors on fat cells Included in Jeme's network theory was the proposal of the rat and, in addition, induce some of the biologi that the paratope of an anti-Id molecule (anti-anti- cal effects of insulin. This was the first strong experi X) might in some instances bear a structural resem mental evidence supporting Jerne's concept of an blance to an epitope on the external antigen, X. Jeme intemal image. The interaction with cellular receptors, used the term "intemal image of the antigen" to de especially if the appropriate biological effects are me scribe such a stmcture on the anti-Id antibody. Sub diated, is perhaps more convincing than the induction sequent evidence supporting the validity of this of antibodies as evidence for structural relatedness of concept led to the proposed use of anti-Id antibodies antigen and anti-Id. It seems unlikely, for example, as vaccines (Nisonoff and Lamoyi, 1981; Roitt et al., that the insulin receptor would bear much structural 1981). resemblance to an anti-insulin antibody outside the in sulin binding region. CRITERIA FOR STRUCTURAL SIMILARITY 3. Competition of Antigen and Anti-Id for Binding OF EPITOPES ON THE ANTIGEN (X) AND to Anti-X antibodies ANTI-ID This is a rather weak criterion because only partial 1. Capacity of the Anti-Id to Induce the Synthesis overlap may be needed for steric interference with of Anti-X Antibodies binding. This of course is a key element of structural relatedness 4. Comparison by X-ray Crystallography of the because it is directly relevant to the capacity of the Interaction of Antigen and Anti-Id with the Same anti-Id to act as a surrogate antigen in a vaccine. (The Antibody question of T-cell stimulation will be considered later.) However, the experiment is not convincing if, as some This is obviously the ultimate method for comparing times reported, it is carried out in an animal that is structures on the antigen and anti-Id that make con syngeneic with the donor of the anti-X antibodies used tact with the antibody. Results obtained by this tech to generate the anti-Id. Within an inbred strain the same nique will be considered later. idiotype may be present on many B cells. Such cells may be activated to produce anti-X antibodies by an anti-Id reagent directed to an epitope outside the DEGREE OF STRUCTURAL RELATEDNESS antigen-binding region; in this case there would be no BETWEEN THE ANTIGEN AND ANTI-ID requirement for a structural resemblance of the anti- Id and the antigen. Such an anti-Id would, however, This question is of critical importance with respect to probably fail to stimulate the formation of anti-X anti the potential use of anti-Id reagents as vaccines. The bodies in a heterologous species; thus, a mouse anti- large number of instances in which anti-Id reagents Id with these properties would not be useful as a have been successfully used to induce antibodies to a vaccine in humans. Because some idiotypes are cross- variety of antigens, including pathogens (e.g., reactive even in different strains of mice, a mouse anti- Schoenfeld et al., 1994; Thanavala and Pride, 1994; Id should be tested for its capacity to induce anti-X in Bona and Moran, 1985; Nisonoff, 1991), leaves no another species. If, for example, it stimulates anti-X doubt that the appropriate B cells can frequently be antibodies in rabbits it seems quite possible that it will stimulated by such immunization. However, the pre also do so in humans. cise nature of the structural similarity between the antigen and anti-Id is relevant to another question, antigen and antibody V regions were scanned for namely, whether the anti-Id can activate antigen- maximum homology. Stretches of 8—25 amino acids specific T cells. For many pathogens, as well as tumors, were generally compared. T-cell responsiveness is known or predicted to be es Such studies clearly indicate that certain anti-Ids sential for the prevention or cure of the disease. MHC share partial amino sequences with the antigen. In ad restriction and T-cell recognition are based on linear dition, direct evidence for the induction by anti-Id of amino acid sequences whereas antibody interactions cellular immunity specific for external antigens, in involve the three-dimensional structure of the anti cluding pathogens and tumor antigens, has been re gen. With respect to interaction with an antibody mol ported by a number of laboratories (Nepom et al., 1984; ecule, even if the contact amino acids in the antigen Lee et al., 1985; Williams et al., 1989; Mellstedt et al., and anti-Id were identical this would provide no guar 1991; Velge-Roussel et al., 1991; Chatterjee et al., antee of appropriate similarity of linear sequences in 1993; Durrant et al., 1994; Herlyn et al., 1994; Yang the epitopes responsible for T-cell stimulation. and Thanavala, 1995; Chakraborty et al, 1995; Durrant The amount of published data relevant to the ques et al., 1995; Foon et al., 1995). T-cell involvement is tion of structural resemblance is limited. Bruck et al. implied in all of these studies and a direct demonstra (1986) demonstrated a significant resemblance be tion of T-cell activation was made in several instances. tween amino acid sequences of a monoclonal anti-Id and the antigen under investigation (type 3 reovirus hemagglutinin). About half of a 16-amino acid se X-RAY CRYSTALLOGRAPHIC INVESTIGA quence of the hemagglutinin shows homology with a TIONS OF MIMICRY OF ANTIGEN BY ANTI-ID framework segment of the VH region. The remainder of the 16-amino acid sequence is homologous to a VL X-ray crystallography is the definitive method for dem sequence, mainly from the second CDR. It is of inter onstrating structural resemblance between an epitope est that both the VL and VH peptide sequences showed of the antigen and anti-Id. A limitation is the large cross reactivity with the hemagglutinin at the T-cell amount of effort required and the consequent paucity level. In addition, studies with synthetic peptides of data. Nevertheless, interesting conclusions have indicated that the regions of sequence similarity been derived by comparing the crystal structures of corresponded with the site of attachment of the he Id—anti-Id and Id-antigen complexes. Each crystallo- magglutinin to receptors on cells (Williams et al., graphic study made use of Fab or Fv fragments of a 1989). monoclonal antibody and its monoclonal anti-Id. Another example comes from the laboratory of A crystallographic investigation by Garcia et al. Fougereau (Mazza et al., 1985). The antigen used was (1992) demonstrates one mechanism by which mim a random copolymer of glutamic acid, alanine and tyro icry may occur. With angiotensin II (All) as the exter sine. The DH regions of several monoclonal anti-Ids nal antigen they generated Abl, Ab2 and Ab3. The contained the sequences tyr-tyr-glu or glu-glu-tyr that mouse monoclonal Ab3 was found to bind All with are closely related to immunodominant sequences of high affinity. Of particular interest was the observa the antigen. tion that, in binding to Ab3, the All antigen adopted a With thyrotropin as the antigen, Taub et al. (1992) conformation very similar to that of a loop in CDR3 detected sequences resembling those of the antigen in of the light chain of an (unrelated) myeloma protein; the CDR regions of two anti-Id mAbs. Synthetic this might well account for the apparent mimicry of polypeptides based on these sequences interacted with All by Ab2, i.e., the ability of Ab2 to induce anti-All. thyrotropin receptors on rat thyroid cells and inhibited By X-ray analysis Bentley et al. (1990) found no certain biological effects of thyrotropin in vitro. A evidence for structural similarity (mimicry) of the moderate amount of sequence homology was also ob epitopes of the antigen, lysozyme, and the Fab of anti- served between a heavy chain CDR sequence in a Id that interact with the same antibody. The authors monoclonal anti-Id and a 23-amino acid sequence of claimed that the anti-Id expressed an internal image a known epitope of the antigen, hepatitis B surface of the antigen according to serological criteria. How antigen (Pride et al., 1992; see also Taub et al., 1989). ever, this conclusion was based on the induction of It should be noted that the degree of sequence ho anti lysozyme antibodies, by immunization with anti- mology observed in these investigations rarely ex Id (Ab2), in the same strain (BALB/c) that provided ceeded 50% despite the fact that the sequences of the the Abl. As discussed above such an immunization