Medical Intervention Chapter 7 Immunology

• the immune system is designed to defend the body against foreign or dangerous substances that invade it
• foreign or dangerous substances include

  • microorganisms (microbes)
  • parasites
  • cancer cells
  • transplanted organs & tissues
• microbes: germ such as bacteria, viruses, fungi, and parasites
• antigens: substances that stimulate an immune response in the body
• antigens may be contained within or on:

  • bacteria
  • viruses
  • microorganisms
  • cancer cells
• some antigens may exist on their own as food molecules or pollen
• foreign: a substance that is not recognized as belonging to the body
• a normal immune response consists of:

  • recognizing foreign antigen; the immune system has to recognize self versus non-self
  • mobilizing forces to defend against it; having an army of cells and components that will fight the foreign substance
  • attacking it; attacking means to fight off the infection
• autoimmune disorder: a malfunction of the body's immune system that causes the body to attack its own tissue; an immune response against itself
• examples of autoimmune disorder:

  • ulcerative colitis (treatable but long-term)
  • chron's disease (treatable but long-term)
  • bullous pemphigoid (treatable)
  • lupus (deadly)
  • type 1 diabetes (treatable but long-term)
• immunodeficiency disorders: a malfunction of the immune system resulting in infections that develop and occur more frequently, are more severe, and last longer than usual
• examples of immunodeficiency disorders:

  • HIV
  • AIDS
• allergic reactions or hypersensitivity reactions: an inappropriate response to a normal, harmless substance
• anaphylaxis: a severe allergy
• first line of defense of the immune system:

  • skin
  • cornea of the eye
  • membranes lining the respiratory, digestive, urinary, & reproductive tracts
• second line of defense of the immune system:

  • involves white blood cells that travel through the blood stream & into tissues which search and attacks microbes and other foreign invaders
  • this defense has 2 parts: nonspecific (innate) immunity & specific (adaptive) immunity
  • both interact with each other directly or through substances that attract or activate other cells of the immune system
• nonspecific (innate) immunity: involves several types of white blood cells that usually act on their own to destroy foreign invaders; they can directly attack any foreign substance on its own
• specific (adaptive) immunity: involves white blood cells and components that work together to destroy foreign invaders; it takes time for the attack, it learns how to be effective, and sometimes requires assistance
• substances that attract or activate other cells of the immune system:

  • cytokines: messengers of the immune system
  • antibodies: immunoglobulins (proteins)
  • complement proteins: proteins that act in a sequence (domino effect) to destroy foreign pathogens
• to be able to destroy invaders, the immune system must first recognize them
• must be able to distinguish what is nonself (foreign) from what is self
• foreign: a cell with molecules on its surface that are not identical to those on the body's own cells
• every person has a unique HLA
• the immune system can make this distinction because all cells have identification molecules on their surfaces
• in people, identification molecules are called human leukocyte antigens (HLA), or the major histocompatibility complex (MHC) and they produce an immune response
• microbes are recognized because they have unique, foreign identification molecules on their surface
• HLA recognizes antigens and MHC presents antigens
• some white blood cells (B lymphocytes) recognize invaders directly
• others (T lymphocytes) need help from other cells of the immune system called antigen presenting cells
• bone marrow: a soft, fatty, substance in the cavities of bones in which blood cells are produced
• the human thymus becomes much smaller at the approach of puberty
• "b" in b lymphocytes means "bursa of fabriscus" or bird bone marrow
• thymus: a lymphoid organ situated in the neck of vertebrates that produces T cells for the immune system
• lymph: a clear, watery, sometimes yellowish fluid derived from the body tissues. it contains white blood cells and circulates throughout the lymphatic system
• b lymphocyte:

  • lymphocyte derived from the bone marrow
  • remains in bone marrow until it matures
  • provides humoral immunity
  • spreads through the body, but concentrate in the lymph nodes, spleen, & liver
  • circulates between blood and lymph
  • specific to one antigen
• humoral immunity: a component of the immune system that involves antibodies which are secreted by B cells and circulate a soluble proteins in blood plasma and lymph
• lymphatic system: an interconnected system of vessels between the body tissues and organs by which lymph circulates throughout the body
• b cells only make one type of antibody molecule
• one specific antibody for one specific antigen
• two major types of b lymphocytes:

  • plasma cells: b cells that reproduce antibodies which are released into the blood, lymph, lining of the lungs and gut, and are released at several one thousand per second
  • memory b cells: b cells that have the ability to realize foreign antigens that were previously encountered