Immunity

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Immunity

• Anatomy Physiology
• Tony Serino, Ph.D.
• Biology Department
• Misericordia Univ.

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Immune System

• Provide defense of the body against infectious
  agents, toxins, foreign bodies, and cancers
• Two types of defenses
• General (Non-specific or Innate) Defense
• Barriers
• Normal Flora and Fauna
• Fever
• Surveillance
• Inflammation
• Non-specific Phagocytic WBCs and NK cells
• Protective Chemicals
• Specific (Adaptive) Defense --Lymphocytes

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Barriers

• Prevent infectious agents from penetrating
  internal environment
• Epithelium ( thickness, tight junctions,
  keratin)-especially the skin
• Cilia and mucus
• Watery secretions (tears, saliva)
• Acidity (stomach, urine, vaginal secretions)
• Normal Flora and Fauna resident bacteria prevent
  infectious agents from growing on body surfaces

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Fever

• Rise in Body Temperature
• Inhibits invading cell growth increase body
  metabolism to increase defense/repair cell
  activity
• Produced by release of pyrogens from leukocytes
• Low grade fever is beneficial in fighting
  infection, high sustained fever may be life
  threatening

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Surveillance

• Number of cells and organs to detect invading
  agents
• Langerhans cells of skin, Mast cells, Dendritic
  cells, and organs like Tonsils, GALT cells
• Gather antigens and present them to lymphocytes

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Inflammation

• Allows more blood defenses into damaged areas
• Triggered by release of paracrines from damaged
  tissues (PG), attacking WBCs (cytokines), mast
  cells (heparin and histamine), and activation of
  blood protective chemicals (complement and
  bradykinins)
• Increases
• blood flow through vasodilation (hyperemia)
• capillary permeability
• Both lead to local edema
• If prolonged or systemic, can become life
  threatening

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Inflammatory Response
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Phagocytic WBC and NK cells

• WBCs can distinguish the sugars in mammalian
  cells and those found on bacteria or other
  parasites
• PMNs, macrophage, and mast cells can injure or
  destroy cells that do not display normal sugars
• NK cells related to T-cells but attack any cell
  not displaying MHC I proteins
• Kill by secreting perforins and other chemicals

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Phagocytosis
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Protective Chemicals

• Chemicals that aid in destroying or retarding
  infectious agents
• Interferon cytokine released when cell attacked
  by virus warns other cells in area
• Lysozyme antibacterial enzyme present in tears
  and saliva
• Complement blood proteins which can detect and
  destroy bacteria

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Interferon
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Complement
MAC membrane attack complex (C3-C9)
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Specific (Adaptive) Immunity

• Individual targets are selected for attack by the
  lymphocytes that can bind that target (antigen)
• Antigens (Ag) any large substance not normally
  found in the body these illicit an immune
  response (immunogenic and immuno-reactive)
• Haptens are small molecules that can trigger an
  immune response only if bound to larger molecules
  (like pollen, some cosmetics, detergent
  fragrances, poison ivy animal dander and drugs)
  they are immuno-reactive but not immunogenic by
  themselves

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Antigenic Determinants
Large macromolecules illicit immune response
because they have many sites to which immune
molecules will attach proteins have the most of
any molecule
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Identifying Self from Non-self

• T-cells migrate to thymus, B-cells remain in bone
  marrow (the primary lymphoid tissues)
• Become immunocompetent -selected for their
  ability to produce a surface receptor against an
  antigen and to tolerate self antigens
• Those that bind weakly to self-antigens are
  selected, the others are eliminated
• The strongest self-antigens are the MHC proteins
• Once competent, the cells are released to move
  through the blood and aggregate in the secondary
  lymphoid tissues

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Thymic Selection
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Movement of Lymphocytes
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Cells Involved in Specific Immunity

• Lymphocytes (B and T cells) -attack antigen
  bearing agents either chemically (humoral
  immunity the B-cells) or physically (cellular
  immunity the T-cells)
• T and B-cell activation to an antigen works best
  when they are presented with the antigen by
  another cell
• APCs (Antigen Presenting Cells) (macrophage,
  surveillance cells, B-cells, infected cells)
  display foreign antigenic determinants on their
  MHC II cell surface proteins to activate the
  lymphocytes

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Memory T cell
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B-cell Clonal Expansion
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Antibody Structure
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Antibody Actions
Opsonization Ag-Ab complex makes ID for
phagocytosis easier
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Humoral Response
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Control of Lymphocyte Response

• B-cells can be activated by the antigen alone,
  but it is more effective if they are presented
  the antigen by APCs or stimulated by T-helper
  cells
• Activation of T-helper cells stimulates complete
  lymphocyte response

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MHC I found on all bodys cells except RBCs
Surface proteins usually bound to pieces of
intracellular proteins, but when infected they
present fragments of the infectious agent
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MHC II found on APCs
-bound to phagocytized outer coat molecules of
immuno-agent
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T-cell Types
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Helper T-cells
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Clonal Selection of T-cell
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Cytotoxic T-cell Attack
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Primary Immune Response
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Vaccine Production
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Types of Acquired Immunity
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Acute Allergic Reaction
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Pathologies

• AIDS HIV invades T-helper cells, diminishing
  effectiveness of immune response may have as
  long as 8 year incubation time, 100 fatal
• Autoimmune Diseases Immune system targets
  naturally occurring compounds of the body
  (usually sequestered proteins) MS, rheumatoid
  arthritis, Diabetes mellitus (I), etc.
• Cancer cancers cells spontaneously form during
  life, but the immune system keeps them in check
  failure results in tumors and metastasis