Immunology *2

• Antigens

  Generally, bigger and more complex is better
• Poor Antigens

  • Simple molecules
  • Small, unattached molecules
  • Large but repetitive molecules
• Good Antigens

  COMPLEX whole proteins
• Antibody Functions

  • Comes through mucous membranes
  • Causes allergic reactions
• Major Histocompatibility Complex (MHC) surface proteins

  • MHC I proteins are found on all nucleated cells and are necessary for cell recognition
  • MHC II proteins are found only on "antigen-presenting cells" like macrophages and B cells and are particularly important in T helper cell activation
• The Specific Immune Response

  The "Third Line of Defense"
• Overview of the Specific Immune Response

  1. Engulfment, digestion, and presentation of antigens by a dendritic (phagocytic) cell

  2. Lymphocyte development

  3. Presentation & activation

  4. Initiation of Humoral Immunity

  5. Initiation of Cell-Mediated Immunity

  
• Presentation & Activation

  • Monocytes (and sometimes B cells) come in contact with antigen (generally pieces of an invader)
  • Monocytes "process" antigen which activates specific T-helper cells
  • T-helper cells then activate specific B cells, which produce antibodies

  
• Initiation of Humoral Immunity

  • Activated B cells differentiate into plasma cells and memory B cells
  • Plasma cells go on to produce specific antibodies which was activated by T-helper cells

  
• Initiation of Cell-Mediated Immunity

  • "Naïve" T cells are activated to form more T-helper, cytotoxic ('killer') T, and Memory T cells
  • Cytokines that regulate immune system also released

  
• Generation of Unique Receptors with Unique Antibodies and Clones

  • As lymphocytes develop, genes involved in antigen binding are rearranged so each clone only produces a single receptor... forever
  • Any clones that target "self" molecules are eliminated
  • A specific antigen selects only the clone(s) that match it, initiating an immune response

  
• 1. Cell Receptors

  • Similar in function and structure to antibodies on B cells
  • Variable (V) regions and constant (C) regions
  • Recognize specific antigens presented by phagocytes
• Activation of T-helper cells by Antigen Presenting Cells (APCs)

  Activation of B cells and Antibody Production and Cytokine Storms

  
• Superantigens and Cytokine Storms can be deadly