After studying this chapter, you should be able to:
- Understand the concept of stem cells and their importance.
- Summarize the causes of the major disorders affecting red blood cells.
- Discuss the general structure of the red blood cell membrane.
- Know the biochemical bases of the ABO blood group substances.
- Indicate the major biochemical features of neutrophils and understand the basis of chronic granulomatous disease.
- Appreciate the importance of integrins in health and disease.
Blood cells have been studied intensively because they are obtained easily, because of their functional importance, and because of their involvement in many disease processes. The structure and function of hemoglobin, the porphyrias, jaundice, and aspects of iron metabolism are discussed in previous chapters. Table 52–1 summarizes the causes of a number of important diseases affecting red blood cells; some are discussed in this chapter, and the remainder are discussed elsewhere in this text. Anemia is a very prevalent condition with many causes. The discovery of the causes of certain types of anemias (eg, of pernicious anemia [a form of B12 deficient anemia] and of sickle cell anemia) has been an area where the reciprocal relationship between medicine and biochemistry referred to in Chapter 1 has been extremely beneficial. The World Health Organization (WHO) defines anemia as a hemoglobin level of <130 g/L in men and <120 g/L in females. There are many causes of anemia; only the most prevalent or biochemically relevant are mentioned here. A simplified classification of the causes of anemia is given in Table 52–2. It has been estimated that some 300,000 children are born each year with a severe inherited disorder of hemoglobin, the majority in low- or middle-income countries. Because infant mortality is decreasing, many of these children will survive to present a global health problem. Certain of the blood group systems, present on the membranes of erythrocytes and other blood cells, are of extreme importance in relation to blood transfusion and tissue transplantation. Every organ in the body can be affected by inflammation; neutrophils play a central role in acute inflammation, and other white blood cells, such as lymphocytes, play important roles in chronic inflammation. Leukemias, defined as malignant neoplasms of blood-forming tissues, can affect precursor cells of any of the major classes of white blood cells; common types are acute and chronic myelocytic leukemia, affecting precursors of the neutrophils; and acute and chronic lymphocytic leukemias. Knowledge of the molecular mechanisms involved in the causation of the leukemias is increasing rapidly, but is not discussed in any detail in this text. Combination chemotherapy, using combinations of various chemotherapeutic agents, all of which act at one or more biochemical loci, has been remarkably effective in the treatment of certain of these types of leukemias. Understanding the role of red and white cells in health and disease requires a knowledge of certain fundamental aspects of their biochemistry.
Table 52–1 Summary of the Causes of Some Important Disorders Affecting Red Blood Cells