Knowledge of mechanisms involved in the pathogenesis of occlusive arterial dis eases is fundamental for the design of prevention and treatment. A series of studies based on in vitro investigations, the experimental animal and the human being have slowly increased our understanding of cardiovascular diseases and unveiled their secrets to us. Over the last 60 years it has been generally assumed that dietary fats and lipids and the occurrence of atherosclerosis are closely related. Yet, even if epidemiological studies clearly indicate the existence of an association between the amount of composition of dietary lipids and morbidity and mortality of cardio vascular disease, our basic knowledge on cause and effect is still hidden in a cloud of uncertainty. The present book discusses the relation between dietary lipids and arterial throm bosis, which latter process has been observed in the coronary arteries in up to 90% of subjects with acute myocardial infaction. In this volume Dr. Hornstra, who has occupied himself with thrombosis research with never-failing enthusiasm, great skill and critical approach for the last fifteen years, tries to establish possible links between lipid metabolism and thrombosis. His literature studies are comprehensive and his investigations are impressive in that they give a new dimension and a new methodology to research of lipids and thrombosis."

United States government. Defense Nuclear firms, Hoffman-LaRoche and Ciba-Geigy, and by Agency, Armed Forces Radiobiology Research In- the American firm, Travenol. stitute. SIEGMUNDJ. BAUM Furthermore, we greatly appreciate the gener- G. DAVID LEDNEY ous financial support by the Swiss pharmaceutical vi Xlll List of Contributors Part I Regulation of Stem Cell Proliferation L. G. Lajtha 1 Regulation of Stem Cell Proliferation 3 L. G. Lajtha and E. G. Wright Introduction 3 Experimental Evidence 3 Summary 7 References 7 Contents 2 Surface Antigens of Hemopoietic Stem Cells: The Expression of BAS, Thy-1, and H-2 Antigens on CFU-s 9 Ger van den Engh, Jim Russell, and Diane de Cicco Introduction 9 Materials and Methods 10 Results 11 Discussion 13 Summary 14 Acknowledgments 14 References 15 3 The Regulation of Hemopoiesis: Effect of Thymosin or Thymocytes in a Diffusion Chamber 17 S. J. Sharkis, A. Ahmed, L. L. Sensenbrenner, W. W. Jedrzejczak, A. L. Goldstein, and K. W. Sell Introduction 17 Materials and Methods 17 Results 18 Discussion 20 Summary 21 Acknowledgments 21 References 21 4 Anti-CFU-s Activity of Rabbit Anti- mouse Brain Serum: Mechanism of Action 23 Solomon S. Adler, Richard D. Kuznetsky, and Frank E. Trobaugh, Jr. Introduction 23 Materials and Methods 23 Results 26 Discussion 29 Summary 31 Acknowledgments 31 References 31 vii Contents Part II Ralph van Furth, Theo J. L. M. Goud, and Physiology of Committed Dick van Waarde Stem Cells 33 Introduction 65 D.

xi List of first authors xiii Acknowledgements xv INTRODUCTICN Approaches to radiolabelling blood d-c cells: past, present and future M. L. Thakur 3 CELL LABELLllJG TEDlNIQUES 2 Labelling techniques of granulocytes and platelets 17 with 111 In-oxinate M. R. Hardeman, E. G. J. Eitjes-van Overbeek, A. J. M. van Velzen, M. H. Rovekarnp 111rndium-labelling of human washed platelets; kinetics 3 29 and in vivo sequestration sites M. Eber, J. P. Cazenave, J. C. Grob, J. Abecassis, G. !o1ethlin 111Indium loss from platelets by in vitro and ex 4 44 vivo manipulation R. J. Hawker, C. E. Hall, H. C-oldman, C. N. McCollum PIATELEl'S: KrnETIC STUDIES 5 The maturation of megakaryocytes and their precursors 65 J. H. Paulus 6 !o1egakaryocytic precursors 74 J. Breton-Gorius, W. Vainchenker 7 !-1ethods of quantification of platelet production 86 in man. A critical analysis Y. Najean vi 8 Platelet production rate deteDmination with (75se)_ seleno-m:thionine R. Cardinaud, E. Dassin 96 9 Platelet kinetics: the state of the art A. duP Heyns 110 10 Platelet kinetics A. M. Peters 130 Evaluation of models to deteDmine platelet life 11 span and survival curve shape M. G. LOtter, C. P. Herbst, P. N. Badenhorst, A. duP Heyns, P. Wessels, P. C. Minnaar 139 12 Canparison of three m:thods evaluating platelet survival tim: in patients with prosthetic heart valve J. Schbath, D. Ville, B. Hathy, B. Sanchini, E. Benveniste, J. Belleville, M. Dechavanne, J. P. Boissel, J.

The practice of transfusing blood started at the bedside but over the last few decades blood transfusion has become more and more a laboratory directed discipline. The emphasis on serology and laboratory controlled measures has made blood transfusion safer and more effective, but laboratory and clinical aspects of the discipline have tended to become increasingly separated. As a result of this separation clinical developments in blood transfusion may not have derived full benefit from the knowledge accrued in blood transfusion services. Over the last five years the Red Cross Blood Bank Groningen-Drenthe has organised yearly symposia with a clinical theme in order to bring blood banks and clinicians closer together. Many of the recent major advances in clinical medicine have been based on developments in blood transfusion practice. This is certainly true for paediatric medicine. For instance, in paediatric oncology, including leukemia, cell separator programmes have made available new forms of support. Further, blood component therapy has provided an effective means of control in some of the bleeding disorders of children. Some of these topics are discussed in this symposium dealing with intensive care. Haemolytic disease of the newborn and exchange transfusion are other aspec.ts of intensive care. Our purpose in dealing with them was twofold.

G. F. FUEGER Among the many processes in Physiology few appear mo e inviting to be studied by tracers and external imaging than the variety of the routes of migratory (blood) cells in health and disease. Much emphasis has been placed lately on the methods of labelling of the white blood cells. It is obviously quite important and necessary to refine the methods of leucocytic labelling, particularly to search for ways to label selectively a specific group of white blood cells, but there is also the need to review and keep abreast with the developing knowledge of the white blood cells themselves, especially their behaviour under pathological conditions, as seen by histology and scintigraphy, their biological properties, their immunological characteristics and the mechanisms of the control of leucocytic functions. Similarly, it appears desirable to analyze animal models of inflammation as well as to review the dosimetry and the biodistribution of labelled white blood cells in humans. This book is the result of a cooperative effort to review certain highlights of the physiology of leucocytes, labelled and unlabelled, as a corollary to the effort concerning the labelling of white blood cells. In preparing this book we aim for a better understanding and definition of the goals to be achieved by the successful labelling of the migratory cells of the body. XI CONTRIBUTORS Becker, H. Medizinische Universitaetsklinik der Uni versitaet Graz, Graz, Landeskrankenhaus, haus, Austria Bjurman, B. Department of Radiation Physics, General Hospital, Malmoe, Sweden Chiles, C."

Where do you begin to look for a recent, authoritative article on the diagnosis or management of a particular malignancy? The few general oncology text books are generally out of date. Single papers in specialized journals are informative but seldom comprehensive; these are more often preliminary reports on a very limited number of patients. Certain general journals frequently publish good in-depth reviews of cancer topics, and published symposium lectures are often the best overviews available. Unfortunately, these reviews and supplements appear sporadically, and the reader can never be sure when a topic of special interest will be covered. Cancer Treatment and Research is a series of authoritative volumes that aim to meet this need. It is an attempt to establish a critical mass of oncology literature covering virtually all oncology topics, revised frequently to keep the coverage up to date, and easily available on a single library shelf or by a single personal subscription. We have approached the problem in the following fashion: first, by dividing the oncology literature into specific subdivisions such as lung cancer, geni tourinary cancer, pediatric oncology, etc.; and second, by asking eminent authorities in each of these areas to edit a volume on the specific topic on an annual or biannual basis. Each topic and tumor type is covered in a volume appearing frequently and predictably, discussing current diagnosis, staging, markers, all forms of treatment modalities, basic biology, and more."

Plasma fractionation and blood transfusion are inherently linked. Blood bankers need to have a sincere interest in fractionation and purification techniques in order to understand the need for carefully controlled source material collection and initial processing. Developments point to a shift in technology, implementation and application of plasma fractions to be produced, such that early anticipation from both bloodbankers and fractionators in a joint interest and effort are needed. As usual there is good news and bad news. We are referring in that respect to the exciting presentation about the future of bloodbanking. Although the blood donor still plays a major role in bloodbanking, new technologies could terminate the conventional blood transfusion service in the next 20-40 years. Sooner or later DNA technology will play an important role in bloodbanking and bloodbankers will have to deal with cultivated red cells as a replacement of our donor blood. Several fractionation techniques like column chromatography, controlled pore glass chromatography, heparin double cold precipitation technology and polyelectrolite fractionation are available, which may result in better yields for some of the plasma proteins. These techniques are likely to replace in part the old Cohn fractionation in the near future.

Bone marrow transplantation has emerged as a major form of treatment for a broad range of human diseases. Marrow transplantation has many unique biologic features and its principles differ markedly from the transplantation of solid organs. This volume overviews the present status of bone marrow transplantation and summarizes recent progress and controversies. Ad vances in defining the underlying biology of marrow transplantation are discussed. The current status of several major clinical problem areas are reviewed, including engraftment, acute and chronic graft-versus-host dis ease, immunodeficiency, and opportunistic infections. The therapeutic role of allogeneic and autologous bone marrow transplantation is discussed, and results are compared with alternative therapies. lX List of contributors ANASETII, CLAUDIO, M. D. , Fred Hutchinson Cancer Research Center, 1124 Columbia Street, Seattle, Washington 98104 APPELBAUM, FRED, M. D. , Fred Hutchinson Cancer Research Center, 1124 Columbia Street, Seattle, Washington 98104 ARMITAGE, JAMES 0. , M. D. , Department of Internal Medicine, Univer sity of Nebraska Medical Center, 42nd and Dewey Avenue, Omaha, Nebraska 68105 BEATIY, PATRICK G. , M. D. , Fred Hutchinson Cancer Research Center, 1124 Columbia Street, Seattle, Washington 98104 BIERMAN, PHILIP J. , M. D. , Department of Internal Medicine, Univer sity of Nebraska Medical Center, 42nd and Dewey Avenue, Omaha, Nebraska 68105 BUTTURINI, ANNA, M. D. , Department of Pediatrics, University of Parma School of Medicine, Parma, Italy CHAMPLIN, RICHARD, M. D.

AIMS OF THE COLOGNE-SYMPOSIUM ON RADIOLABELLED PLATELETS In 1976, M. Thakur et al (1) were the first to publish a paper concerning the in vivo thrombus detection with 111- In-labelled platelets. Previous attempts at scintigraphic thrombus localisation had been disappointing because of the unspecific binding of a number of the isotopes used, as well as the poor labelling efficiency or an insufficient low gamma-emitting property. Because of its physical characteristics (2.8 days half-life, 94% gamma emission) 111 Indium turned out to be the best isotope for platelet kinetic studies as well as for the measurement of platelet incorporation by Thrombi to be used up until now. The lipophile complexes of Ill-In (8-hydroxyquinoline, acetylacetone, tropolone) diffuse passively into the platelets without altering the function or the life span of the platelets. This advantage has let to an increase in the clinical applications of 1211-In labelled platelets. Today, radiolabelled platelets are used for thrombus detection in several different medical areas such as cardiology, nephrology. angiology or neurology. Even though many scientists and hospital doctors now routinely use radiolabelled platelet as a diagnostic tool, there is as yet not a standardized labelling method. In addition to this, there are neither standardized image procedures for the different clinical applications nor an agreement about specificity and sensitivity of the method. In 1983, a symposium on Radiolabelled Cellular Blood Elements was organized by M.Thakur, M.R.Hardeman and M.D.

Hairy cell Leukaemia (HCL) has always attracted an interest out of all proportion to its frequency and continues to do so. There are two reasons for this. The first is that the disease is unusually responsive to therapy and second is that it has provided a number of important insights into B-cell biology. This monograph is a comprehensive account of hairy cell leukaemia and aims to provide a more detailed account than is available in the existing literature. The work is timely because a consensus has now emerged concerning accurate differential diagnosis a nd curative treatment. These aspects therefore form the focus of the book and are considered in detail. The basic advances in the laboratory that encourage the belief that elucidation of the underlying oncogenic event in the disease may be within reach. The background to this belief is extensively renewed. As a result the monograph will be of interest and practical value to both clinicians and researchers in this and related fields.

Human Lymphoma: The Clinical Implications of the REAL Classification is a unique volume. It is based on the recent developments in classification and overall understanding of human lymphoid neoplasms which are relatively common neoplasms and which epidemiological evidence suggests are increasing in frequency. This field has been the cause of confusion in the past as a result of conficting ideas on the classification of lymphoma and related diseases. However a new vision of the field has emerged and the is encapsulated in the pioneering REAL classification and in a forthcoming WHO scheme, both of which are covered in the book. The volume will appeal to hematologists, pathologists and oncologists and will, thanks to a diverse and expert authorship, serve to increase the working knowledge of all three groups.

An up-to-date overview of blood coagulation, hemostatis, and thrombosis, this volume also provides a state-of-the-art report of current anti-thrombotic and anti-coagulant strategies as well as a summary of current research interest in the area and potential future targets. It attempts to balance traditional pharmacology with the newer sciences of molecular biology and in so doing, sets a framework for future advances in the field. The book is a concise, current and useful reference for the basic researcher as well as the practicing physician working in the fields of cardiology, internal medicine or surgery.

This volume documents our growing understanding of the human major histocompatibility complex. The application of this information is ever more important as the limits of transplantation continue to be reduced, including the recent success of bone marrow transplantation between unrelated but closely matched individuals. In addition, the need to transfuse platelets in the face of immunologic barriers continues to challenge transfusion services. Thus, the serologic information summarized in this volume is essential for optimal patient care. At the same time, recombinant DNA technology has led to a revolution in our understanding of many aspects of basic biology. Among the advances has been the initial characterization of the structure of some HLA loci. While this will ultimately improve clinical services, constant reference to serologic data is essential so that the powerful new techniques can be applied in the most effective ways. The timing of the First Red Cross International Histocompatibility Workshop is fortunate as it brings together experts from around the world to address the state of the art. We are all grateful to Dr. John Lee and his colleagues for organizing the workshop, and for bringing together in this volume the material to be presented in Beijing during October 17-23, 1990. Leon W. Hoyer, M.D.

This volume presents the proceedings of the Fourth Annual Symposium on the Molecular Biology of Hemopoiesis, held in Reno, Nevada, November 1 and 2, 1988. Its focus on erythropoiesis represents an attempt to cover a rapidly expanding field, which has gone from elegant studies of erythro poietin physiology, to molecular biology, to clinical applications and again to physiology. The rapid development has been made possible by cloning of erythropoietin gene and the availability of recombinant hormone. The regulation of heme and its derivatives has also been aided by techniques of molecular biology; there is now a concerted effort to better understand how these enzymes contribute to proliferation, differentiation and maturation of the erythron. Globin gene derrangements have been targets of recent research in an attempt to correct the defect by genetic engineering. In the chapters of this book, several groups "expressed" their views on this subject. Finally, we analyze various regulators of erythropoiesis, both in vivo and in vitro. Dr. Richard Levere was a pioneer in many studies of heme metabolism and of erythropoiesis. He has been a generous supporter of research in this field and of our past meetings. It is only. fitting that this volume should be dedicated to him."

The rapid and continuous upsurge of interesting data in the subject of tumor immunology necessitates the publication of an annual series to furnish the updated materials to the students, researchers, and clinicians in this rapidly advancing field. Concepts and methodologies are ever changing. Also, current research in tumor immunology promises to offer breakthroughs in the future. Important is the need to communicate to the right people the exact role of immunodiagnostic methods and immunolog ical intervention in cancer prevention and treatment. The role of immuno therapy in combination with conventional modalities of treatment needs in its proper perspective. Oncogene, interferon, lympho to be understood kines, monoclonal antibodies, natural killer cells, platelet-mediated cyto toxicity of antibody-coated target cells, suppressor cells, platelet-derived factors, plasma-blocking factors, control of suppressor cell function, ab rogation of plasma-blocking factors, etc., are some of the areas that are continually advancing. Progress in these areas will have implication in cancer therapy. Further, it is already understood that if immunocompe tence of the host can be maintained at a reasonably good level, there exists the potential to increase the therapeutic indexes of conventional modalities of treatment. This series will attempt to present updated infor mation in all these areas based on contributed and solicited articles. P. K."

The theme of this 14th International Symposium on Blood Transfusion is closely related to the work and scientific contributions of the Dutch cryobiology pioneer Dr. Herman W. Krijnen of the Dutch Red Cross Central Laboratory. Dr. Krijnen was known and respected in the national and interna tional blood transfusion community as an extremely competent scientist and a beloved and admired colleague. Dr. Krijnen was intentionally honoured with the invitation to open this symposium on cryopreservation and low temperature biology in blood transfusion and be the guest of honour at this event. Unfortunately, Dr. Krijnen suddenly died on the first of June 1989. In honour and mem ory of Dr. Krijnen this symposium will therefore be dedicated to him. Since the lOth International Symposium on Blood Transfusion in 1985 highlighted the theme of "Future developments in blood banking", major changes have occurred in the blood banking world. Most of these changes were forced upon the Blood Banks by the fear of spreading AIDS through contaminated donations. This not only led to the wide spread testing of blood, but also to a more appropriate counselling of the community and the blood donors in specific. Additionally, virus inacti vation techniques were introduced for those components derived from multiple donations and intended for a regular transfusion in haemophi lia patients and others.

During the past decade, there have been numerous direct and indirect scientific contributions to both the etiology and therapy of aplastic anemia and related bone marrow failure syndromes. Clinical observations, such as autologous bone marrow recovery after conditioning with immunosup pressive agents for bone marrow transplantation; failure to achieve en graftment in some identical twins without prior immunosuppressive ther apy; and hematologic response to immunosuppressive agents, have led to the concept of immune-mediated etiology of acquired aplastic anemia. Such a concept was further strengthened by laboratory findings, implicat ing the role of activated cytotoxic T lymphocytes and abnormal produc tion of inhibitory lymphokines. The immunologic mechanisms may also apply to the idiosyncratic bone marrow aplasias associated with drugs, toxic chemicals, and viruses. These agents may alter normal cellular recog nition sites by interacting with cellular components and result in loss of self tolerance. Immunologic mechanisms have long been advocated in many other organ failures, and the hemopoietic organ is no exception. It is of interest that parallel clinical and laboratory investigations in juvenile diabetes mellitus type I and in rodent models of this disease have yielded results compatible with the same pathogenic mechanisms. The infiltration of pancreatic islets by activated T lymphocytes, functional and morphological alterations of islet cells upon incubation with lymphokines such as gamma interferon and tumor necrosis factor, and clinical response to cyclosporine are a few examples."

An overview of diagnosis and current management of myelodysplastic syndromes.

- Reviews the performance of the pharmacological treatments currently available and analyses the potential for new treatments
- High quality clinical photos and figures to enhance descriptions and improve reader comprehension
- Useful reference text for healthcare professionals needing to know more about myelodysplastic syndromes

In 1628 William Harvey published his discovery of the existence of the microcirculation which he deduced from careful anatomical and physiological study. Thirty-three years later, Malpighi confirmed the presence of capillaries through direct microscopical observation. Subsequent scientific advance has been slow, and in view of the fact that microvascular in the genesis and expression of many pathophysiology may be implicated diseases, our know ledge of human microvascular function is surprisingly limited. This ignorance attests to the difficulty of studying something that is both minute and inaccessible without disturbing the quantity that is being measured. In the last fifteen years, however, direct techniques have been developed for studying human microvascular pressure, flow and permeability. These methods have provided new insights into human microvascular function in health and disease. At the same time there has been a steady growth of new indirect techniques based on a w ide range of physical principles that reflect some or other aspect of microvascular function.

Cytokines are cellular growth factors which also provide communication between cells and their milieu. This clearly is an exciting area in modern medicine that will have significant impact on various facets of transfusion. Erythropoietin therapy stimulates red cell production while thrombopoietin seems to positively affect megakaryopoiesis and can be an added armamentarium for the thrombocytopenic patient. Using haematnopoietic growth factors, stem cells could be mobilized early to the peripheral blood for collection and subsequent transplantation into haemato-oncology patients instead of bone marrow transplantation. Using a cocktail of cytokines in cell culture, stem cells could be expanded and selected for therapy. Cytokines and growth factors can even be modified, which may lead to successful gene therapy in malignancies, including solid tumour vaccines. However, the presence of cytokines in certain blood products could have biological effects following transfusion, although its clinical relevance needs to be ascertained. There is much potential for the use of cytokines in the treatment of infections. Early diagnostic methods are now available to monitor their levels and relevance. It is likely that cytokines will increasingly play a role in therapy and could develop our fundamental knowledge about the development of T-cells. An ethical dilemma remains, however, regarding the use of cytokines in healthy donors for harvesting suitable specific cells. Longer clinical observation will be necessary to gather the necessary information. Cytokines and growth factors in blood transfusion was the theme of the 21st International Symposium in Blood Transfusion, where twenty clinicians and scientists, experts in their own fields, were invited to update the above information. Their findings are presented in four sections in this volume: Fundamental aspects - cytokines in development of T-cells, growth factors in haematopoiesis, growth factor receptors and signal transduction, cytokine response in platelet and whole blood transfusions. Function, production and diagnosis &endash; laboratory diagnostics of cytokines and growth factors, cytokines in blood components, cytokines and growth factors in cell expansions, cytokines for genetic modification towards gene therapy, progenitor cells from healthy donors. Application in clinical medicine &endash; clinical relevance of cytokines in transfusion products, cytokines and growth factors in solid tumours, gene therapy in malignancies, vaccine strategies inducing T-cell immunity against tumours, cytokines in the treatment of infections, thrombopoietin and megakaryopoiesis. Future potential use in transfusion medicine &endash; erythropoietin, immunotherapy, ethical aspects of the use of cytokines and growth factors in donors, potential of cytokines and growth factors in transfusion medicine.

All medical specialists who must contend with the possibility of thrombosis will be interested in Anticoagulation. This book evaluates anticoagulation procedures from various points of view - from Current Trends in Anti-thrombotic Drugs, to Treatment of Ischemic Vascular Disorders; from Anticoagulants in Pregnancy, to Anticoagulation in the Elderly, from the Effects of Anticoagulant Therapy on the Heart, to Anticoagulation in various Surgical Procedures. Anticoagulation is a resource of approaches to the management of this common medical problem.

A rapid increase in our understanding of the biology of platelets and their role in disease in recent years has been paralleled by increasing successes with established platelet-modifying therapies in many clinical conditions. This text focuses on the clinical role of platelets in a wide variety of haematologic, cardiovascular and other disorders, providing a practical, clinically relevant handbook for all clinicians and researchers interested in platelets and their role in disease. Covering platelet physiology, bleeding disorders, thrombotic disorders and antithrombotic therapy. Chapters cover all the conventional and less conventional aspects of platelet involvement in disease, with an emphasis on recent clinical developments. Clear take home messages have been included in each chapter to aid clinical practice. With contributions from leading experts across three continents, Platelets in Hematologic and Cardiovascular Disorders is an up-to-date, well illustrated, practical resource for everyone involved in clinical practice with platelet disorders.

This volume constitutes the proceedings of a satellite symposium of the XXXth congress of the International Union of Physiological Sciences. The symposium has been held In Banff, Alberta Canada July 9-11 1986. The program was organized to provide a selective overview of current developments in cardiac biophysics, biochemistry, and physiology. In order to highlight areas of develop ing ideas and to stimulate the participants' inquisitiveness into the nature and complexity of the integrated cardiovascular system, lectures and discussions were presented that emphasized evolving and sometimes provocative concepts in the field. With the same goal in mind we have, for the readers of this volume, briefly summarized the general discussions. We would like to thank several individuals whose dedication made this sym posium and publication of the proceedings possible. Mrs. Lois Kokoski and Mrs. Madeleine Aldridge of the Conference Office of the University of Calgary seemingly effortlessly handled the details of the symposium. Peter de Tombe, Dr. Peter Backx and Dr. Jeroen Bucx transcribed the general discussions. Finally, we appreciate the extra effort of our secretaries, Lenore Doell and Gregory Douglas, and the work of Anna Tyberg who prepared the final manuscripts for publication. Henk E.D.J. ter Keurs, M.D. Ph.D. John V. Tyberg, M.D. Ph.D."

Haemoglobin is one of the most important molecules in the animal kingdom. Its function is to carry oxygen to tissues. In lower invertebrates the blood pigment is present in the haemolymph and is not bound in cells. Later in the course of phylo genesis haemoglobin remains associated with cells which produce it and in this form it reaches the peripheral circulation. In higher organisms the haemoglobin production is thus determined by two main factors: haemoglobin synthesis in erythroid cells and the formation of these erythroid cells which depends on cell proliferation in haematopoietic organs. Human haemoglobin is made up of two chains which combine from four different polypeptide chains formed in varying ratios in different periods of the life cycle. During the life span of humans the following haemoglobins are formed: embryonic haemoglobins Gower 1 and 2, foetal haemoglobin F and two adult haemoglobins A and A . E-and IX-chains are part of the embryonic haemoglobins Gower 1 (E4) and 2 Gower 2 (1X2E2). These haemoglobins predominate in embryos during the second month of pregnancy and at the end of the first trimester they are completely re placed by foetal haemoglobin F ( Y2). Adult haemoglobin A consists of two IX and two -chains and is the main component of red cells in adults. A relatively small component of red cells accounting for less than 2 % of the total haemo globin, is haemoglobin A2 (1X0)."