Immune System

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Immune System
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Defense system
Nonspecific Immunity Specific Immunity
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First line of defense Surface membrane barriers

• Skin and mucous membrane
• Layered epidermis and shedding of epithelial
  cells
• Sebum inhibits growth of bacteria and fungi
• Mucous traps microbes, dust and pollutants.
• Lacrimal apparatus
• Saliva
• Vaginal secretions
• Flow of urine
• Defecation and vomiting
• Gastric juices destroy bacteria and their toxins

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Text Table 21.2
Oral Cavity Antimicrobial enzymes in saliva (e.g. lysozyme and lactoperoxidase) inhibit microbes, Resident flora
Skin pH (3-5), sebum
Respiratory Cavity Hairs, cilia, mucociliary escalator, Sticky mucus (lysozyme) traps dust and microbes.
GI Tract low pH and digestive enzymes, flushing action
Eyes Tears, (lysozyme). flushing action
Vagina pH, flushing action, resident flora
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Second line of defense chemical and cellular
defenses

• Antimicrobial proteins
• Interferon
• Complement
• Transferrins
• Natural killer cells
• Phagocytes
• Neutrophils
• Dendritic cells
• Macrophages
• Wandering
• Fixed
• Eosinophils

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Interferons

• Produced by lymphocytes, macrophages and
  fibroblasts.
• Interfere with translation of viral proteins
• Degrade viral RNA
• Activate macrophages and NK cells
• Interferon Animation

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Complement
Complement Cascade Animation
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Phagocytosis
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Phagocyte Mobilization
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Fever

• Regulated my hypothalamus
• Due to pyrogens secreted my leukocytes
  macrophages
• Causes liver and spleen to sequester zinc and
  iron
• Increases metabolic rate (repair)

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Inflammatory response

• Stages Inflammation Animation
• Release of Chemical Alarms
• Vasodilatation Permeability of BV
• Emigration of phagocytes Dispose cellular debris
  pathogens
• Sets the stage for repair
• Prevent spread of damaging chemicals pathogens
• Signs of inflammation
• Redness
• Heat
• Swelling
• Pain
• Impairment of function

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Comparison of Immune Cells
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Adaptive Resistance

• Specificityrecognition of particular antigens
• Memoryremembers previously encountered antigens
• Systemicimmunity is not restricted to the
  initial infection site
• Immune responses
• Antibody-mediated or humoral immune responses
  (late 1800s)
• Cell-mediated immune responses (mid 1900s)

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T Lymphocytes

• CD4 T cell - also known as a T Helper (Th) cell
• CD8 T cell - also known as a Cytotoxic T (Tc)
  cell

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Antigens and antigen receptors

• Antigens can be entire microbes, parts of
  microbes or chemical components of pollen, egg
  white, blood cells,.

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Self antigens MHC proteins

• Antigens on our own cells are self-antigens
• MHC proteins are glycoproteins that mark the cell
  as self.
• Class I MHC proteins are on all body cells.
  Receptors on TC
• Class II MHC proteins are only on certain cells
  that act in the immune response. Receptors on TH
• Antigen Processing

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Immunocompetence

• T and B cells that have not been exposed to an
  antigen are naïve.
• Binding with an antigen completes differentiation
  into functional B and T cells.
• B cells mature in the bone marrow.
• T cells mature in the thymus.

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Antigen receptors

• Genes determine what foreign substance will be
  recognized.
• An antigen determines which T or B cells will be
  activated.
• Lymphocytes make over a billion different
  receptors.
• Gene segments of a few hundred bits are
  reshuffled and combined--somatic recombination.
• The newly assembled gene is expressed as a
  receptor on the cell surface.

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Humoral immune response

• Antigen challengethe meeting between a naïve
  immunocompetent lymphocyte and an invading
  antigen.
• Occurs in lymphoid tissue such as spleen or lymph
  node.
• If antigen challenge is presented to a B cell
  then the humoral immune response is provoked.

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Clonal SelectionMonoclonal Antibody
Production
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Antibodiesimmunoglobulins
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Immunoglobulin classes

• IgD is attached to B-cell plasma membrane
• IgM is released during primary response.
  Indicates current infection.
• IgG is the most aboundant. Can cross placenta
  blood vessel walls.
• IgA found in body secretions prevents attachment
  to body surfaces.
• IgE causes release of histamine (allergies) by
  attaching to mast cells basophils.

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Immunological memory

• Primary immune response
• Secondary immune response

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Antibody defense PLANe

• Precipitation
• Lysis Complement fixation and activation
• Agglutination
• Neutralization
• Enhancing phagocytosis

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Cell-mediated immunity

• Antibodies can only inactivate an antigen and NOT
  destroy it.
• Antibodies prepare an organism for destruction by
  innate defenses.
• T cells can only recognize and respond to
  processed fragments of protein.
• T cells are suited for cell to cell interaction
  and target body cells infected by virus, bacteria
  and abnormal or cancerous body cells or cells
  that are transplanted or infused.

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Cell-mediated immunity T-cells

• Activation of T cellsT cell receptors bind to
  antigen presented by the antigen-MHC complex.
• CD4 and CD8 proteins interact with antigen and
  help maintain MHC-antigen coupling.
• Types of T-cells
• Helper T cells (CD4)
• Cytotoxic T cells (CD8)
• Memory T-cells

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Activated T cell

• Activation leads to enlargement, differentiation
  and proliferation of T cells.
• T cells that are reproduced are clones of
  originally activated T cell.
• Activation, differentiation and proliferation
  occurs in secondary lymph organs and tissue.
• Activation leads to release of inflammatory
  cytokines.

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Homeostatic imbalances Immunodeficiencies

• Abnormally behaving immune cells
• Severe combined immunodeficiency (SCID) syndromes
• Congenital conditions
• Acquired immune deficiency syndromes
• Hodgkins Disease
• HIV
• AIDS

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Homeostatic imbalances Autoimmune disease

• Tend to be more prevalent in women
• Type I diabetesdestroys pancreatic beta cells
• Multiple sclerosisdestroys myelin sheaths
• Myasthenia gravisimpairs communication between
  nerve and muscle
• Lupus erythematosussystemic disease of skin,
  kidneys, heart, and lungs
• Rheumatoid arthritisdestruction of joints

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Organ transplants

• Autograftsgrafts from the same person to another
  body site
• Isograftsgrafts between genetically identical
  individuals
• Allograftsgrafts among the same species
• Xenograftsgrafts taken from another animal
  species

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HypersensitivitiesHypersensitivity Reactions in
the Skin
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Hypersensitivities
Acute Subacute
Subacute Delayed
Immediate cytotoxic
Immune complex
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Type I Hypersensitivity
Type I Hypersensitivity Animation Type II
Hypersensitivity
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Type III Hypersensitivity
Type III Hypersensitivity
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Animations

• Flash animation of a NK cell interacting with a
  normal body cell.
• Flash animation of a NK cell interacting with a
  virus-infected cell or tumor cell not expressing
  MHC-I molecules.
• Flash animation of apoptosis by NK cells.
• HIV Replication

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Resources

• Components of the Immune System Animation