TRANSES 16

• Immunology


  The scientific study of the immune system and responses
• Immunology


  • Considered as the third line of specific host defense mechanism
  • Involves complex interactions among many different types of body cells and cellular secretions
• Immunologists


  Scientists who study various aspects of the immune system
• Antigens


  Molecules that stimulate the immune system to produce antibodies

  
• Antibodies


  • Proteins produced by the immune system in response to antigens
  • Differentiate between "self" and "nonself" (something foreign)
  • Destroy that which is "nonself"

  
• Humoral Immunity (Antibody-Mediated Immunity "AMI")


  • Always involve the production of antibodies in response to antigens
  • A person is immune to a particular pathogen because of the presence of specific protective antibodies that are effective against that pathogen
  • Antibodies play a major role

  
• Cell-Mediated Immunity (CMI)


  • Involves various types of cells, with antibodies playing only a minor role
  • Involves many different cell types, including macrophages, T helper cells, cytotoxic T cells, delayed hypersensitivity T cells, natural killer cells, killer cells, and granulocytes

  
• Immunity


  The condition of being immune
• Acquired Immunity


  Immunity that results from the active production or receipt of protective antibodies during one's lifetime

  
• Active Acquired Immunity


  • Immunity is acquired in response to the entry of a live pathogen into the body
  • Immunity that results from receipt of a vaccine

  
• Passive Acquired Immunity


  • Antibodies formed in one person are transferred to another to protect the latter from infection
  • Person receives antibodies rather than producing them
  • Immunity is temporary, lasting only 3-6 weeks

  
• Major cell types that participate in immune responses


  • T lymphocytes (T cells)
  • B lymphocytes (B cells)
  • NK cells (a category of lymphocytes)
  • Macrophages

  
• Helper T Cells (T-Helper cells, TH cells, CD4+ cells)


  • The primary function is secretion of cytokines
  • TH1 -support cell-mediated immune responses, involving macrophages, cytotoxic T cells, and NK cells
  • TH2 -support humoral immune responses by inducing B-cell activation and differentiation of activated B cells into plasma cells

  
• Cytotoxic T Cells (T-cytotoxic cells, TC cells, CD8+ cells)


  The primary function is to destroy virally infected host cells, foreign cells, and tumor cells

  
• Regulatory T Cells


  • Serve as a brake on the immune response to infection
  • Include more than one cell type and have multiple functions, including the downregulation of the immune response once an infection has been contained

  
• Where immune responses occur


  • Spleen, lymph nodes, tonsils, and adenoids
  • Lymphatic system is central to immune activity, with the spleen and lymph nodes serving as key sites
  • Mucosal surfaces, like the respiratory and digestive tracts, activate immune responses in associated lymphoid tissues such as tonsils and Peyer's patches
  • Various immune cells collaborate in these sites to generate immune responses

  
• Humoral Immunity


  • Special glycoproteins called antibodies are produced by B cells in response to antigens
  • Antibodies are capable of recognizing, binding to, and inactivating or destroying specific pathogens

  
• Antigens


  • Foreign organic substances that are large enough to stimulate the production of antibodies
  • Antigenic determinants (epitopes) are individual molecules that stimulate the production of antibodies
  • Haptens are small molecules that may act as antigens only if they are coupled with a large carrier molecule such as a protein
  • Most antigens must be foreign materials that the human body does not recognize as self antigens

  
• Processing of antigens in the body

  
• Antibodies


  Glycoproteins produced by B cells in response to antigens

  
• Antibodies


  • Capable of recognizing, binding to, and inactivating or destroying specific pathogens

  
• Antigen


  Foreign organic substance that is large enough to stimulate the production of antibodies

  
• Antigenic substances are capable of stimulating the production of antibodies

  
• Antigenic determinants (epitopes)


  Individual molecules that stimulate the production of antibodies

  
• Hapten


  Small molecules that may act as antigens only if they are coupled with a large carrier molecule such as a protein

  
• Most antigens must be foreign materials that the human body does not recognize as self antigens
• Processing of antigens in the body

  Macrophages, DC's, T cells, and B cells are often involved in a cooperative effort

  
• 1. dependent antigens


  Processing requires the participation of helper T cells, as well as macrophages and B cells

  
• 1. independent antigens


  Helper T cells are not involved, only B-cells

  
• Plasma cells


  Cells derived from B-cells which secrete the antibodies

  
• Primary response


  The initial immune response to a particular antigen, takes about 10 to 14 days for antibodies to be produced

  
• Secondary response (anamnestic response/ memory response)


  The increased production of antibodies after the second exposure to an antigen, occurs more rapidly and with higher antibody concentrations than the primary response

  
• Memory B cells and memory T cells


  Play key roles in immunologic memory
• Antibodies


  Proteins produced by lymphocytes in response to the presence of an antigen, usually very specific, binding only with the antigenic determinant that stimulated their production

  
• Immunoglobulins


  Globular glycoproteins in the blood that participate in immune reactions, including antibodies

  
• Humoral or circulating antibodies

  Found in the blood

  
• Antibody structure


  • Y shaped structure composed of two identical light polypeptide chains, two identical heavy polypeptide chains, and an FC region at the base, with two antigen-binding sites that bind specifically to antigens

  
• Antigen-antibody complex (Ag-Ab complex or immune complex)


  The combination of antibody and an antigen

  
• Antigen–antibody complexes are capable of activating the complement cascade, resulting in effects like activation of leukocytes, lysis of bacterial cells, and increased phagocytosis as a result of opsonization

  
• Antitoxins


  • Antibodies that recognize and bind to toxin molecules, neutralizing their harmful effects