This chapter describes the fundamental properties of the immune system. The immune system is comprised of white blood cells that fight off infections and it is the immune system that is ultimately destroyed as a consequence of HIV infection. The chapter begins with a description of the physiology and anatomy of the blood (hematopoietic) system and the functions of red blood cells (erythrocytes) and white blood cells (leukocytes). It continues with a description of the development of the immune system and shows how all the diverse cells of the immune system arise from a common stem cell in the bone marrow.
The various classes of white cells and their functions are described, including the central role of helper T cells, the most important cellular target of HIV, in the immune response. The role of T and B lymphocytes in humoral and cell-mediated immunity is explained. The immune system has three fundamental properties- specificity, diversity, and memory- that allow it to recognize a diverse range of foreign invaders and quickly eliminate them from the body. The reader learns in this chapter about B cells that produce proteins called antibodies and how antibody specificity and diversity are generated. The reader also learns how T cells recognize foreign or virally-infected cells and destroys them. The concept of a primary and secondary immune response and how immunological memory forms the basis for vaccination is explained.
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