Immunology: Specific Immunity

1
Immunology Specific Immunity

• Immunity not being susceptible to disease
• Types of immunity
• Innate you have it from birth.
• Species as humans, immune to diseases of many
  other creatures
• Genetic presence/absence of receptors
• Non-specific host defenses Macrophages, etc.
• Acquired after exposure, your body remembers
  specific invader.

2
Other views of immunity

• 2 x 2 matrix Immunity is either active or
  passive either natural or artificial.
• Active means that host is making his own
  antibodies passive means the antibodies came
  from someone else.
• Natural means the antibodies
• were acquired by the host thru
• natural means artificial means
• they were injected.

Active Artificial Active natural
Passive Artificial Passivenatural
3
Nature of antigens

• The immune system recognizes, responds to, and
  remembers molecules that are antigens.
• An antigen
• Is foreign
• Is large
• Is molecularly complex.
• A molecule that is too small to be an antigen
  without piggy-backing onto another is a hapten
• The specific part of an antigen recognized by an
  antibody or receptor is called an epitope.

4
Dual Nature of the immune system

• Humoral and cell mediated
• Humoral refers to body fluids, specifically that
  this branch of the immune system uses antibodies
  which are protein molecules dissolved in blood,
  body fluids, and secretions.
• B lymphocytes are the source of antibodies
• Cell mediated refers to the direct involvement of
  cells to attack an infection
• T lymphocytes either kill cells directly or
  recruit macrophages to kill cells directly

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Basics of antibodies

• Protein molecules produced by activated B cells.
  
• Belong to class of proteins called
  immunoglobulins (Ig), subclass of globulins.
• Y-shaped molecule with hinges
• Ends include variable regions where antigen
  binding occurs.
• Antibodies made by a single B cell are all the
  same, differ from those made by another in
  variable region.

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Basic Antibody structure

• Molecule undergoes shape change upon binding to
  antigen.
• Classic lock key like an enzyme.

Fc end binds to host cells.
7
The Antibodies

• IgG most abundant in blood and body fluids
  single Y shaped molecule, remains in circulation
  for long time.
• IgM 5 Y-shaped units linked together, first type
  of antibody made in an immune response.

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The Antibodies

• IgA present in large quantities in body
  secretions a dimer (2 Y-shaped units, tail to
  tail), helps protect mucous membranes.
• IgE single Y shaped unit, in small quantities,
  found bound to mast cells attached by Fc end,
  involved in allergies (mast cells release
  histamine).
• IgD The receptor for antigen normally found on
  the surface of B cells if it is shed into
  bloodstream, looks a lot like an IgG antibody.
  In very small amounts.

9
Memory and antibody titer
Upon first exposure to antigen, accumulation of
antibody is slow. Memory cells make for a
quicker, larger response afterwards.
This is the basis for booster shots.
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The Immune response

• An immune response is what the immune system does
  when confronted by an antigen.
• An immune response is an elaborate interplay
  between antigen, non-specific defenses, and B and
  T lymphocytes.
• The process involves direct contact (cells,
  molecules bind to receptors on cell surfaces) and
  cytokines (messenger molecules) that also bind to
  receptors on cell surfaces.

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Take Immunology to learn the details of how an
immune response happens

• Now for more on antibodies, vaccines, and
  hypersensitivities.

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How DO antibodies help?

• Antibodies attach to antigens. Period. But
• Because there are at least 2 binding sites,
  cross-bridges form, linking antigens together in
  clumps.
• Attaching covers up critical sites on the
  antigens.
• Agglutination Aby links cells, viruses together
  to make clumps that attract macrophages.
• Precipitation toxin molecules come out of
  solution, can be cleared out.
• Neutralization toxins, viruses no longer active.

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How DO antibodies help?-2

• Opsonization an opsonin is something that
  promotes phagocytosis.
• By making antigens into clumps.
• By providing a handle (Fc end of antibody).
• Complement fixation
• Antibody binds to antigen, antibody changes shape
• Shape change activates complement
• Activated complement leads to increased
  inflammation, opsonization, and cell lysis.

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Vaccines

• From vaccus, Latin for cow, from Ed Jenner
  using cowpox to immunize.
• Live attenuated vaccine
• Pathogen grown to make it weak, used alive.
• Killed/inactivated vaccine
• Destroyed with formalin, weaker immune response
• Subunit/conjugate/engineered
• A portion of pathogen used, often combined with
  another molecule for effectiveness antigen may
  be produced through genetic engineering.

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Hypersensitivities-1

• Inappropriate immune responses
• Type II are cytotoxic reactions like the Rh
  factor problem and bad blood transfusions.
• Rh is one of many blood groups, like ABO
• An Rh fetus in an Rh- mother means she gets
  immunized by babys blood cells, makes Aby.
• Second pregnancy, fetal RBCs are attacked.
• Solution give Rho-gam during 1st pregnancy.
• Type III are immune complex disorders, where too
  many agn-aby clumps cause inflammation.

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Hypersensitivities-2Allergies

• Type I are immediate type, in which antigen binds
  to IgE on mast cells, histamine released.
• Histamine smooth muscle contraction,
  vasodilation.
• Results in asthma, diarrhea, shock depending on
  where antigen enters body. Ex. Bee sting.
• Type IV are delayed type, T cell produces various
  cytokines which affect macrophages.
• The bar fight scenario come, stay, get angry.
• Angry macrophages cause much tissue damage.
• Ex. Poison ivy urushiol-coated cells killed.