Autoimmune Diseases

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Autoimmune Diseases

• Occasionally the immune system loses the ability
  to recognize the bodys own cells. The immune
  system then begins destroying the bodys own
  organs or tissues. This is called and autoimmune
  disease.
• It is not clear why this happens in all cases. 4
  types of autoimmune diseases
• 1. Autoimmunity
• Antibodies made by the body that attack body
  tissues or organs.
• May be due to antibodies made in response to
  foreign antigens, on microorganisms, with a
  similar sequence to the body cells proteins. The
  immune system is unable to distinguish between
  the two proteins because they are so similar.

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• 2. Cytotoxic
• Mistaken antibody reactions to cell-surface
  proteins.
• Myasthenia gravis muscles become progressively
  weaker due to antibodies that bind to
  acetylcholine receptors on nerves that reach the
  muscles
• Eventually muscles fail because do not receive
  the proper chemical signals.
• Usually results in respiratory arrest and death
• It is not known why the body makes antibodies to
  a chemical receptor like this.
• 3. Immune Complex
• Just like with the hypersensitive immune complex
  disease, this type of autoimmune disease is
  caused by clusters of antibody/antigen deposited
  in the body.
• Rheumatoid arthritis immune complexes deposited
  in joints.
• Causes chronic inflammation and leads to severe
  damage to cartilage and joint due to the immune
  systems efforts to get rid of the immune complex
  deposits.

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• 4. Cell-mediated
• Insulin-dependent mellitus immunological
  destruction of insulin-secreting cells of the
  pancreas.
• T cell dysfunction is implicated in disease.

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Diagnosing Infections
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Phenotypic Methods manifest characteristics.

• Microscopic Examination
• Gram Stain, Acid Fast Stain, Fluorescence
  Antibody Test, and Antigen Testing are all quick
  ways to diagnose common infections.
• Cultivation
• Selective media and Differential media
• Motility, Oxygen requirements, cultural appearance

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• Biochemical Testing
• Carbohydrate fermentation (lactose, sucrose,
  glucose, etc.)
• Enzymes produced (catalase, oxidase, bile
  esculin, etc.)

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Genotypic Methods what the genes say.

• DNA Analysis
• Hybridization small fragments of DNA (probes)
  of known sequence attach to unknown DNA. When
  they attach, the organisms is identified!
• rRNA Analysis
• Sequence of bases in ribosomes.
• PCR
• Used to sequence a known gene for a particular
  organism. If the gene is replicated then that
  organism is known to be present in the sample.
• GC base content
• Each genus has differing amounts of A/T to C/G
  ratios within DNA. This technique is more useful
  in determining ancestral relationships rather
  than identifying a microorgansim.

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Immunological Methods

• Antigen-Antibody Rxns
• Agglutination and Precipitation Rxns
• Whole cell of the sample organism combined with
  Ab for a suspected organism. This test is
  conducted on a slide. If the Antibody (Ab)
  matches the organism in the sample, the
  antibodies will bind to the organism and visible
  clumps will form in the solution.
• Ag with Ab (saline agar plate). This is the same
  concept as the one above however it is conducted
  on an agar plate and the antigen/antibody
  reaction is seen within the agar.
• Western Blot
• Used for HIV confirmation
• The western blot is a combination of gel
  electrophoresis, to separate specific proteins in
  a sample, and an antigen/antibody reaction.
• Once the proteins (possible HIV antibodies) are
  separated on the gel, HIV antigens are added to
  see if they will bind to any of the protein bands
  from the gel. If any of the antigens bind, then
  that sample is positive for antibodies for HIV.

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• ELISA (Enzyme-Linked Immunosorbent Assay) Used
  for HIV screen tests.
• See Figure 17.16
• 1. The known antigen, anti-HIV, is adsorbed to
  the well.
• 2. The serum samples from the patient are then
  place in the well.
• If the serum contains antibodies for HIV, they
  will bind to the antigen.
• 3. An indicator molecule is put into the well
  that will bind to the HIV antibody if it is still
  present.
• When it binds to the antibody it catalizes a
  reaction that releases a dye.

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• I didnt go into a lot of detail on most of these
  techniques because I felt that most of them were
  pretty self explanatory.
• If you more help understanding them please email
  me or talk to me about it in class on Friday.