Chapter 12 Learning Objectives Define the following terms:Humoral immunity Antibody isotype Isotype switching Mutation Affinity maturation T-dependent antigens T-independent antigens Cross-linking Follicular helper T cells Follicular dendritic cells Extrafollicular focus Germinal center Mantle zone Follicle Hapten Conjugate vaccine AID Somatic (hyper)mutation Immune complex Alternative RNA processing SHIP Fc receptor Mucosal immunity Neonatal immunity Terminal differentiation Immunogen Learning Objectives - Important concepts to know At the end of this chapter, you should be able to: 1. Explain the process of B cell activation from the time a naive mature B cell is shown antigen for the first time until it produces secreted antibodies. A timeline of events may be helpful. Some items to think about include: a. What provides signal #1 and signal #2? b. What types of things can activate a B cell? c. What receptors are involved? d. What is the consequence of B cell activation? e. What antibody isotypes are produced? f. What cytokines are involved? g. What is the difference between the primary and secondary immune response? 2. Describe the morphology and list the functions of plasma cells. How are plasma cells different from B cells?3. Outline the various pathways in which antigens are delivered to B cells in the lymph node including the role cytokines play in this process (please note: B cells are also found in lymphoid follicles in the mucosa of the respiratory and digestive tracts – we well talk more about this later in the semester). 4. Describe how B cell activation differs from T cell activation. How does activation of T-dependent B cells differ from T-independent B cells? 5. List examples of T-dependent and T-independent antigens. 6. Explain the difference between T-dependent and T-independent responses. What cells are involved and where are these responses taking place? 7. Compare and contrast the three subsets of B cells including (a table may be useful): a. if they are activated by T-dependent or T-independent antigens b. the location where each of these subsets of B cells are found c. the types of plasma cells they produce (short-lived or long-lived) d. the antibody isotype(s) that can be produced 8. Describe the changes that occur within B cells once they are activated (hint: there are four of them). What are the consequences of these changes (what can the B cells in turn do)? 9. Describe the interaction between B cells and helper T cells. a. Describe the role chemokines play in activating T-dependent B cells. b. Identify the location in which B cells and T cells interact with one another. 10. Explain what is interesting about the antigen that is used to activate naive CD4+ T cells and the antigen used to activate T-dependent B cells. 11. Explain the hapten-carrier effect, including: a. What is a/the hapten? b. What is a/the carrier? c. What is the purpose/benefit of using a hapten-carrier? d. What real-life application is this particularly useful for? 12. Identify the T cell zone and B cell zone in the lymph node.13. Describe the germinal center reaction, including: a. the purpose and consequence of forming a germinal center b. the organization of the follicles within the lymph node c. identifying the regions within the follicles d. identifying the types of cells you would expect to find in each of the regions of the follicle e. describing the events that occur in each of the regions of the follicle f. Be sure to note any important molecules required for cell-cell interaction 14. Describe the process of isotype switching, including: a. the cells involved b. the cytokines involved c. the antibody isotype produced as a consequence of the cytokine d. the effector functions of the specific antibody isotypes e. the mechanism of isotype switching (what is happening at the DNA/RNA/protein level, including the enzyme required for gene rearrangement) f. the consequence of isotype switching 15. Explain the correlation between antibody structure and effector function. 16. Explain the process of affinity maturation, including: a. the purpose of affinity maturation b. the mechanism of affinity maturation c. the difference between low-affinity and high-affinity antibodies d. the location where these changes are taking place (in the antibody and in the human body) 17. Explain the purpose and consequences of antibody testing (hint: what cells survive and what cells undergo apoptosis?).18. Compare the structural difference between a membrane-bound antibody and a secreted antibody. What mechanism allows the production of these two forms of antibodies? 19. Compare primary and secondary antibody responses, including: a. the antigen the immune response is stimulated by b. the time it takes to produce a maximum antibody response c. the relative amount of antibody produced d. the antibody isotypes produced e. the relative amount of memory cells produced f. the type of plasma cell involved (short-lived or long-lived) g. the benefits of the secondary antibody response 20. Discuss the mechanism and importance of B cell inhibition (how we stop B cell activation). Please look up the following information in your textbook: In the textbook on Chapter 9, which of the figures in the chapter describes the hapten-carrier effect? Which component is recognized by the B cell and which component is recognized by the T cells? Please read the section on the “Role of CD40L:CD40 Interaction in T-Dependent B Cell Activation: on page 248-249 and answer the following questions: What is the role of the interaction between CD40 and CD40L in activating B cells? Using Figure 12-13 on p. 251, describe the process by which T-dependent B cells are activated (hint: in your answer, include the cells and their movement within the lymphoid organ). X-linked hyper-IgM syndrome - What is it and what is it caused by? What are the effects of this