Immunology

• What is 80% of periodontal destruction due to?

  Host immune response rather than bacteria directly
• What is an immunoglobulin?

  An antibody produced by plasma cells
• What happens when a B Lymphocyte meets its specific antigen?


  • proliferates and differentiates
  • creates plasma cells, memory cells
  • All the plasma cells produce an antibody to the antigen
  • IgG or IgA or IgM or IgD or IgE antibody
  • the relative number of cells producing antibody: IgG>IgA>IgM>IgD>IgE5
• What is the major class of Antibody?

  • IgG
  • blood, tissue fluid (incl GCF)
  • 75% of the total serum immunoglobulin level.
  • defends against toxins, spreading micro-organisms.
  • predominant in the secondary immune response.
• What is an opsonin?

  a substance present in serum which promotes phagocytosis of bacteria
• Are IgG antibodies effective opsonins?

  Yes!! - facilitates phagocytosis
• What two forms does IgA occur in?

  • found in serum, cannot activate the complement system here
  • Secretory IgA found in respiratory and gastrointestinal surfaces and sweat, tears, saliva and colostrum
  • antiseptic - covering parts of pathogens, inhibiting their adherence to surface mucosal cells
  • activate the complement system in the presence of Lysozyme to kill some organisms
• What is the difference between primary and secondary response?

  Primary - first interaction with a pathogen.

  Secondary - body already dealt with pathogen, and launches a second response
• What is the largest of the immunoglobulin molecules?

  IgM - Earliest antibody response in a primary immune response, but it is short lived. Most natural antibodies, such as the blood group AB iso agglutinins are IgM class
• What is the complement system?

  Serum proteins produced by the liver that assist the immune system in destroying microbes Complex group of enzymes in the blood
• Are there high or low levels of IgD in the blood?

  LOW - Cannot activate the complement system, About half of the antigen specific receptors on B lymphocyte membranes are composed of IgD antibodies
• What individuals are high levels of IgE found in?

  Allergic individuals
• Which two ways can the complement system be activated?

  The classic pathway, The alternative pathway
• What is the classic pathway of the complement system?

  • Starts by activating complement factor C1 and then the others in more or less numerical order(C1,4,2,3,5-9)
  • mechanism adopted by the antigen-antibody complexes
  • IgG and IgM can activate C1
• What is the alternative pathway of the complement system?

  • Replaces the first 3 factors of the classical pathway (C1, C4, C2,) with factors D and B which directly activate C3
  • follows same terminal stages as the classical pathway
• What does an activated complement system cause?

  • release histamine from mast cells- produces vasodilation, increased vascular permeability - broncho-constriction
  • Attraction of polymorphs (PMNs) to the site
  • Induces phagocytosis of immune complexes
  • activated complement molecules adhere to macrophages and polymorphs
  • When C8/C9 become activated, produce membrane damage by phospholipase activity
• What else can activate the complement system?

  Structural components (e.g endotoxin) or products (e.g proteases) of bacteria, can activate the complement system by an alternative pathway
• What is the role of the Complement system?

  • increase blood flow and vascular permeability
  • allows antimicrobial factors in blood to “leak” into the tissues
  • Attracts polymorphs to the site
  • Encouraging immune adherence and phagocytosis of the pathogens or foreign cells by the phagocytes
• How does cell mediated immunity work?

  Works through the T Lymphocytes End results are effected by

  • effector T cells (cytotoxic T cells and lymphokine producing T cells)
  • macrophages which are recruited and activated by T cell lymphokines
• What is cell mediated immunity involved in?

  1: Resistance to infections

  2: Tumour rejection

  3: Delayed hypersensitivity states

  4: Regulation of the immune system
• How do T cells regulate the immune system?

  • helper/suppressor cells
  • Form immune regulating system for both cellular and humoral (extracellular) immunity
• What do stimulates T cells differentiate to become?Activated/effector T cells Either:

  a) Lymphokine producing T cells

  b) Cytotoxic T cells (kill cells expressing antigen on their surface membrane)
• What can Lymphokines do?

  • attract & activate phagocytes
  • kill cells (lymphotoxin)
  • activate fibroblasts and other cells (e.g. natural killer cells)
  • Lymphokines and cytotoxic T cells also damage tissues, promote inflammation
• What are Lymphokines?

  • Non-immunoglobulin polypeptide substance
  • Synthesised by T lymphocytes
  • Enhance / suppress an immune response
  • Lymphokines may facilitate cell proliferation, growth, and differentiation
  • Regulate cell function
  • Lymphokines either: Paracrine effect (Local effect acting on cells) Autocrine effect (An action on the same cell that synthesised it)
• What are the function of inflammatory cells?

  • attracted from bloodstream to site of inflammation
  • arrested and stimulated to accelerate phagocytosis and degradation of pathogens
  • macrophages phagocytosed pathogen
  • lysosomal enzymes released to digest pathogens, cause substantial cell damage when released extracellularly, eg rheumatoid arthritis
• Is rheumatoid arthritis a systemic disease with a relationship to periodontal disease?

  yes
• alternative pathway is complex, but its end result is the same as that of the classical pathway and the two mechanisms often function together
• function of polymorphonuclear leukocytes:

  • phagocytosis
  • releases lysozomes
• function of macrophages:

  • phagocytosis
  • release of lysosomes
  • releases powerful regulatory proteins that signal immune system to send additional phagocyte cells to the site of infection
• function of B-Lymphocytes/plasma cells?

  production of immunoglobulins
• t-lymphocytes function?


  further stimulates immune response
• Immunoglobins IgG, IgM, IgA, IgD, IgE?

  • neutalise bacteria or bacterial toxins
  • coat bacteria to facilitate phagocytosis
  • activates compliment system
• complement system function?

  • lysis of cell membrane of certain bacteria
  • phagocytosis
  • recruitment of additional phagocytic cells to the infection site and clearance of immune complexes from circulation