Immunology chapter 6 lecture 1
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Immunology Chapter 6, Lecture 1. Richard L. Myers, Ph.D. Department of Biology Southwest Missouri State Temple Hall 227 Telephone: 417-836-5307 Email: [email protected] Homepage: http://creative.smsu.edu/biology/myersr/index.html TopClass: http://creative.smsu.edu.

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Immunology Chapter 6, Lecture 1

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Immunology chapter 6 lecture 1

ImmunologyChapter 6, Lecture 1

  • Richard L. Myers, Ph.D.

  • Department of Biology

  • Southwest Missouri State

  • Temple Hall 227

  • Telephone: 417-836-5307

  • Email: [email protected]

  • Homepage: http://creative.smsu.edu/biology/myersr/index.html

  • TopClass: http://creative.smsu.edu


Antigen antibody interactions

Antigen-Antibody interactions

  • Similar to enzyme-substrate reactions

  • Involves noncovalent interactions

    • between epitope and CDRs of antibody

    • the reaction is very specific

      • used in diagnosing disease

      • monitoring level of the humoral response

      • identifying certain molecules

  • Ag-Ab reactions differ and speed and sensitivity


Strength of ag ab reactions

Strength of Ag-Ab reactions

  • Involves noncovalent interactions

    • hydrogen bonds

    • ionic bonds

    • hydrophobic interactions

    • van der Waals interactions

  • Requires many of these interactions

    • operating over a small distance (1 angstrom)

  • Therefore, depends upon a very close fit


Antibody affinity

Antibody affinity

  • Defined as the strength of the sum total of noncovalent interactions

  • Low-affinity antibodies bind antigen weakly

  • High-affinity bind more tightly

  • Ag-Ab association can be determined by equilibrium dialysis


Antibody avidity

Antibody avidity

  • Defined as the strength of multiple interactions between multivalent antibody and antigen

  • IgM has a low affinity compared to IgG, but has a high avidity


Cross reactivity

Cross-reactivity

  • Ag-Ab reactions are highly specific, but

    • Ab may cross-react with an unrelated Ag

    • affinity is usually less

  • An example of a cross-reacting Ab is the ABO blood-group antigens

    • originally elicited by microbial antigens

    • will cross-react with similar antigens on RBCs


Precipitin reactions

Precipitin reactions

  • Results when antigen and antibody interact

  • Forms a lattice that becomes visible

    • antibody must be bivalent

    • called precipitins

  • Reaction may take place in fluids

    • dilute the antibody, hold antigen constant

    • used as a rapid test for presence of Ag or Ab

      • the interfacial or ring test is very useful


Precipitin reactions cont

Precipitin reactions (cont)

  • Reactions may occur in gels

    • produces a visible line of precipitation

    • called immunodiffusion

      • used to determine relative concentration of Ag or Ab

      • used to compare antigens

      • or determine relative purity of an antigen

  • Mancini method (radial diffusion)

    • antigen placed in a well

    • diluted antibody placed into agar


Precipitin reactions cont1

Precipitin reactions (cont)

  • Ouchterlony method

    • double diffusion in agar

    • antigen and antibody diffuse toward each other

    • form visible precipitation line where they meet

    • show relationships between different systems

      • identity

      • nonidentity

      • partial identity


Precipitin reactions cont2

Precipitin reactions(cont)

  • Immunoelectrophoresis

    • seperation of proteins with electrophoresis

    • followed by double diffusion in gel

    • can detect concentrations of 3 - 20 mg/ml

    • rocket electrophoresis is similar but can detect level of protein as low as 0.2 mg/ml

  • 2-D immunoelectrophoresis

    • electrophoresis followed by overlay with gel with antiserum


Assignment

Assignment

  • Read Chapter 6, Antigen-Antibody Interactions

  • Review question 6 (pg 163)


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