Chapter 21 Resistance and the Immune System: Acquired Immunity Chapter Summary and Essay Questions Chapter 21 continues to look at the immune system. Then the immune system is discussed as the center of specific resistance. A major section is devoted to the antigen–antibody reaction because it is fundamental to immunology. On completing the chapter, you should be able to answer the following essay questions: a. Describe the four important attributes of acquired immunity. b. Define antigens. State the chemical composition of antigens. Describe their size, and name three types of antigens. c. Distinguish between humoral and cell mediate immunity. d. Identify the types of T- and B-cell receptors, and assess their importance to antigen recognition. e. Explain how the clonal selection activates only those B and T cells that recognize “nonself” antigens or epitopes. f. Discuss the cellular origins of the immune system cells in the human body. g. Describe in detail how humoral immunity operates by defining the cells and processes involved. h. Outline the chemical structure of an antibody molecule, and compare the structure and functions of the five types of immunoglobulins. i. Distinguish between a primary antibody response and a secondary antibody response. j. Briefly describe how gene arrangements can generate novel antibodies. k. Summarize the ways the humoral response assists the clearanceof antigens (pathogens). l. Describe in detail how cell-mediated immunity operates by defining the cells and processes involved. m. Justify the need for cytotoxic T cells as part of the acquired immune response. Identify the difference in function of TH1 and TH2 cells to the acquired immune response.