Biology of Immune Response

• What is the first step in the biology of immune response?

  Recognition of antigen
• What is the role of antigen-presenting cells (APCs) in the immune response?


  They carry antigens to the lymph nodes
• How do APCs display peptide antigens to T cells?


  Via major histocompatibility molecules
• What distinguishes Class I MHC from Class II MHC?


  Class I MHC presents endogenous antigens, while Class II MHC presents exogenous antigens
• What type of T cells are activated by Class I MHC?


  CD8+ T cells
• What type of T cells are activated by Class II MHC?


  CD4+ T cells
• What is required for the activation of naïve T cells?


  Co-stimulation from antigen-presenting cells
• Which proteins do APCs need to provide for T-cell activation?


  CD80 and CD86
• What is the role of T-helper cells in the immune response?


  They orchestrate the immune response via cytokine secretion
• What cytokines do Th1 cells secrete?


  Interferon-gamma, interleukin-2, and tumor necrosis factor-alpha
• What is the function of Th2 cells?


  To control the clearance of extracellular parasites
• What cytokines do Th17 cells produce?


  IL-17 and IL-22
• What is the role of T regulatory (Treg) cells?


  To suppress the immune response to self-antigens
• What percentage of CD4 antigen do Treg cells possess?


  5%
• How do cytotoxic T cells destroy infected cells?


  Through cell-to-cell contact and initiating apoptosis
• What do CD8+ cytotoxic T cells recognize?


  Intracellular antigens
• What are the two primary strategies used by cytotoxic T cells to kill their targets?


  Release of cytotoxic granules and ligation of death receptors
• What are the two toxic substances released by cytotoxic T cells?


  Perforins and granzymes
• What is the main goal of the immune response to T-dependent antigens?


  To destroy the antigen with the help of T cells
• What do B cells require to become activated by T-dependent antigens?


  Binding of surface immunoglobulins to the immunoglobulin receptor
• What happens when CD40 on B cells binds with CD40 Ligand on T-helper cells?


  It delivers activating signals to the B cells
• What is the role of cytokines released by T cells in relation to B cells?


  They enhance B cell transformation into plasma cells
• What is the fate of B cells after they undergo cell division?


  They can differentiate into plasma cells or memory cells
• What is the most common class of immunoglobulin?

  IgM
• What is immunoglobulin isotype switching?


  It is the process by which B cells change the type of antibody they express
• What is affinity maturation in the immune response?


  It is the process by which immunoglobulin binds with increasing strength to an antigen
• What is the main characteristic of the immune response to T-independent antigens?


  T cells are not required for activation
• What is the main goal of the immune response to T-independent antigens?


  Production of IgM
• What happens to B cells when they encounter T-independent antigens?


  They undergo proliferation and differentiation
• What are the key steps in the activation of T cells?


  1. Naïve T cells enter secondary lymphoid organs.
  2. Encounter APCs presenting antigens on MHC molecules.
  3. Receive co-stimulation from CD80 and CD86.
  4. Become activated T cells.