Overview of Cell-Mediated Immunity Flashcards
Describe the types of microbes combated by cell-mediated immunity.
Intracellular microbes that survive within phagolysosomes (bacteria, fungi, protozoa).
Non-phagocytic cells (Infected)
Describe the functions and properties of major cytokines produced by CD4+ helper T cells, including interleukin (IL)-2, IL-4, IL-5, IL-17
IL-2: Proliferation and differentiation of T cells
IL-4: Switching of antibodies to IgE
IL-5: Activation of Eosinophils
IL-17: Stimulate acute inflammation
What are the characteristics and functions of CD4+ TH1
TH1: Releases IFN-y; defends against intracellular microbes
Describe the general process of TH1-mediated macrophage activation.
TH1 cells recognize MHC II on macrophage surface. Binds CD40L on macrophages with CD40. Secretes IFN-y
Explain the phases of cell-mediated immune responses from induction to effector mechanisms.
Induction of Response: Antigen recognition in lymphoid organs, T cell expansion and differentiation, differentiated effector T cells enter circulation.
Migration of effector T cells and to other leukocytes to site of infection: effector T cells encounter antigens in peripheral tissues, activation of effector T cells.
T Cell Effector Functions
Explain the general process by which naïve and effector T cells migrate from the blood to the lymphatic system and to sites of infection.
Migrate from blood to lymphoid organs via high endothelial venules and exit via efferent lymphatics. If they do become activated the migrate out of lymphoid organs via efferent lymphatics and go to the bloodstream. At the site of infection they migrate from the blood through the endothelium in the tissue.
Describe the general features of expansion and decline of T cell responses.
During immune response the survival and proliferation are maintained by co-stimulatory signals.
Once infection is cleared the stimuli disappear and T cells die via apoptosis.
Within 1-2 weeks after cleared infection the response is fully subsided and only memory T cells are maintained. This maintains homeostasis.
Describe the general characteristics and functions of memory T cells.
Some activated T cells differentiate into memory T cells. They are long-lived, found in peripheral lymphoid organs, mucosal tissues and in the circulation. They rapidly proliferate and differentiate into effector cells upon recognition of specific antigen.
What are the characteristics and functions of CD4+ TH2
TH2: Releases IL-4, IL-5 and IL-13; defends against helminthic parasites
What are the characteristics and functions of CD4+ TH17
TH17: Releases IL-17A, IL-17F and IL-22; defends against extracellular bacteria and fungi
Functions of interferon (IFN)-Gamma and transforming growth factor (TGF)-Beta.
IFN-y: Activate macrophages
TGF-Beta: Inhibit T cell activation; differentiation of regulatory T cells
