questions 3

Cells of the Immune System

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Topic updated on 12/23/16 2:11pm

Overview
  • Immune cells have two main lineages This illustration highlights the basic development of various blood cells from hematopoietic stem cells.
    • lymphoid cells (NK cells, T lymphocytes, B lymphocytes)
    • myeloid cells (mast cells, basophils, neutrophils, eosinophils, monocytes/macrophages)
  • Derived from bone marrow hematopoietic stem cells
Lymphoid cells
  • Helper T cells (CD4+)
    • main functions
      • help B cells make antibodies
      • activate macrophages via IFN-γ
    • surface proteins
      • T cell receptor (TCR)
        • antigenic recognition domain
        • α and β chain heterodimer
        • can only bind processed antigens
        • signals through CD3
      • CD3, CD4, CD28 (binds B7), CD40L
    • types
      • TH0
        • "un-decided" naive helper T cell
      • TH1
        • results from strong antigenic insult with macrophage/NK recruitment
          • mainly intracellular bacteria
        • stimulates cell mediated immunity
          • activation of macrophages/NK cells
        • presence of IL-12 and IFN-γ
        • TH1 induced to produce IFN-γ
          • IFN-γ suppresses TH2 development
          • promotes TH1 development
        • high in tuberculoid leprosy
          • less severe than lepromatous leprosy
        • involved in granuloma formation 
          • TH1 secretion of IFN-gamma leads to the development of epithelioid macrophages
      • TH2
        • lack of strong stimuli with no macrophage/NK recruitment
        • stimulates humoral effector mechanisms
        • antibody production
        • TH2 cells produce IL-4, IL-5, IL-10, IL-13
          • IL-4 and IL-10 supresses TH1 development
      • TH17
        • produce IL-17
        • proinflammatory
          • thought to play a role in autoimmunity
  • Regulatory T cells
    • play a large role in preventing autoimmunity by suppressing CD4 and CD8 function
    • produce IL-10, TGF-β
    • surface proteins
      • CD3, CD4, CD25
  • Cytotoxic T cells (CD8+)
    • main functions
    • kill virally infected cells
    • surface proteins
    • CD2, CD3, CD8, TCR
  • B-cells 
    • main functions
      • make antibodies
    • suface proteins
      • B-cell receptor (IgM/D)
        • contains antigenic recognition domain
        • dimer of (heavy chain+light chain)
        • can bind free antigens
        • signals through Ig-α, Ig-β, CD19, CD21
      • MHC II, B7, CD19, CD20, CD21 (receptor for Epstein Barr virus), CD40 (binds CD40L)
  • Plasma cells
    • fully differentiated B cell
    • produce antibodies
  • NK cells
    • main functions
      • kill virally infected cells
      • kill tumor cells
      • kill antibody-coated cells
    • surface proteins
      • CD16, CD56, CD3-, receptors for MHC I
Myeloid cells
  • Monocytes
    • main functions
      • phagocytosis
      • becomes macrophage
    • suface proteins
      • CD14, CD40, B7, receptors for Fc and C3b 
  • Macrophages
    • main functions
      • phagocytosis
      • secretion of cytokines
      • stimulation of healing
      • chronic inflammatory response
    • suface proteins
      • CD14, MHC II, receptors for C3b, Fc 
  • Dendritic cells 
    • main functions
      • antigen capture
      • antigen transportation
      • antigen presentation
    • Langerhans cells = dendritic cells of skin and mucosa 
      • contain Birbeck granules
  • Neutrophils
    • main functions
      • phagocytosis
      • acute inflammatory response
        • especially in systemic infection
      • secretion of cytokines
  • Eosinophils
    • main functions
      • kill antibody coated parasites
  • Basophils
    • main functions
      • allergic response
      • non-phagocytic
  • Mast cells
    • main functions
      • allergic response
        • histamine release


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