IMMUNITY

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IMMUNITY

• BIO 1112

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SPECIFIC IMMUNITY

• Antigen - foreign substance that elicits an
  immune response such as bacteria, viruses, mold
  dust
• Antibodies - proteins produced against antigen
• Vaccination - induced immunity/harmless small
  pox, chicken pox, polio measles
• Active Immunity - antibodies against antigen
• Passive Immunity - antibodies given to individual
  that lasts a few weeks or months

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LYMPHOCYTES

• Originate from stem cells (bone marrow)
• Produce both B-lymphocytes (B cells) and
• T-lymphocytes (T cells)
• Upon maturation (presence of antigen receptors) B
  cells and T cells travel to lymph nodes, spleen,
  etc.

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LYMPHOCYTES
BONE MARROW

• Two kinds of lymphocytes carry out the immune
  response
• B cells secrete antibodies that attack antigens
• T cells attack cells infected with pathogens

Stem cell
THYMUS
Viablood
Immaturelymphocytes
Antigenreceptors
T cell
B cell
CELL-MEDIATEDIMMUNITY
HUMORALIMMUNITY
Viablood
Lymph nodes,spleen, and otherlymphatic organs
Final maturation of B and T cellsin lymphatic
organ
OTHER PARTSOF THELYMPHATICSYSTEM
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ANTIGENIC DETERMINANT
Antibody Amolecules

• Antigens bind to antibodies at specific antigenic
  determinants
• Antigens may have more than one antigenic
  determinant

Antigen-bindingsites
Antigenicdeterminants
Antigen
Antibody Bmolecule
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• An antibody molecule has antigen-binding sites
  specific to the antigenic determinants that
  elicited its secretion

Antigen-binding sites
Light chain
Heavy chain
Figure 24.10B
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ANTIBODY

• Four polypeptide chains both chains have a
  constant and variable regions
• 2 Heavy Chains
• 2 Light Chains
• Variable region recognizes antigen
• Two Major Functions
• Recognize antigen
• Neutralizing antigen

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ANTIBODY

• Weak bonds form between antigen and
  antigen-binding sites on antibody
• Effector Mechanisms
• Neutralization
• Agglutination
• Precipitation
• Activation of complement protein

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Binding of antibodies to antigens inactivates
antigens by
Neutralization (blocks viral binding sites
coats bacterial toxins)
Agglutination of microbes
Precipitation of dissolved antigens
Activation of complement
Complement molecule
Bacteria
Virus
Antigen molecules
Bacterium
Foreign cell
Hole
Enhances
Leads to
Phagocytosis
Cell lysis
Macrophage
Figure 24.11
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CLONAL SELECTION

• Immune System has preexisting B lymphocytes
  that has different antigen receptors
• When an antigen enters the body, it activates
  only lymphocytes with complementary receptors
• B cells multiply into clones of specialized
  effector cells that defend against the triggering
  antigen
• Subsequently B lymphocytes or will produce more
  of the same kind of cell with enlarged ER to
  produce antibodies
• Clone of effector cells have been generated
• T cells may also form a clone of effector cells
  to help humoral immunity

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Antigen molecules
Variety ofB cells in a lymph node
Antigen receptor(antibody oncell surface)
Cell growth division, and differentiation
Clone of manyeffector cellssecretingantibodies
Endoplasmicreticulum
Antibodymolecules
Figure 24.7
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IMMUNE RESPONSE

• Primary Immune Response antigen causes
  production of antibodies in about 2 weeks
• Memory Cells produced and may last for decades
• Second Immune Response production of antibodies
  within a week lasts longer

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T-CELLS

• Battles pathogens that have already invaded body
  cells
• Two types
• Helper T cells activate cytotoxic T cells
  and/or B cells
• Cytotoxic T cells kill other cells
• Bind to infected cells by the antigen-protein
  complex
• Releases perforin that kills infected cells
• Also recognizes cancer cells as foreign intruders
  and kill cancer cells

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• Cell-mediated immunity

• An antigen-presenting cell (APC) first displays a
  foreign antigen and one of the bodys own self
  proteins to a helper T cell

Microbe
Macrophage (will become APC)
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Antigen from microbe(nonself molecule)
Self protein
Self protein displaying antigen
T cell receptor
Bindingsite for self protein
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2
Helper T cell
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Binding site for antigen
APC
Figure 24.13A
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• The helper T cells receptors recognize the
  self-nonself complexes on the APC

• The interaction activates the helper T cells
• The helper T cell can then activate cytotoxic T
  cells with the same receptors

Self protein displaying an antigen
Cell-mediated immunity (attack on infected cells)
Cytotoxic T cell
Interleukin-2 stimulates cell division
T cell receptor
Interleukin-2 activates other T cells and B cells
HelperT cell
APC
Humoral immunity (secretion of antibodies
by plasma cells)
B cell
Interleukin-1 activateshelper T cell
Figure 24.13B
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• Cytotoxic T cells bind to infected body cells and
  destroy them

1
2
Cytotoxic T cell bindsto infected cell
Perforin makes holesin infected cells membrane
3
Infected cell is destroyed
Holeforming
Foreignantigen
INFECTED CELL
CytotoxicT cell
Perforinmolecule
Figure 24.13C
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• Cytotoxic T cells may attack cancer cells
• The surface molecules of cancer cells are altered
  by the disease

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REVIEW

• B cell/T cell
• Antibody heavy/light chain
• Antigenic determinants
• Effector cells
• Clonal selection
• Memory cells
• Humoral immunity
• Cell-mediated immunity

• Active/passive immunity
• Antigen
• Thymus/bone marrow
• 1o vs 2o response
• Function of Antibody
• Perforin
• Interleukin 1 2
• Self/nonself proteins