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Immunology Chapter 5, Lecture 2

Immunology Chapter 5, Lecture 2. Richard L. Myers, Ph.D. Department of Biology Southwest Missouri State Temple Hall 227 Telephone: 417-836-5307 Email: rlm967f@mail.smsu.edu Homepage: http://creative.smsu.edu/biology/myersr/index.html TopClass: http://creative.smsu.edu.

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Immunology Chapter 5, Lecture 2

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  1. ImmunologyChapter 5, Lecture 2 • Richard L. Myers, Ph.D. • Department of Biology • Southwest Missouri State • Temple Hall 227 • Telephone: 417-836-5307 • Email: rlm967f@mail.smsu.edu • Homepage: http://creative.smsu.edu/biology/myersr/index.html • TopClass: http://creative.smsu.edu

  2. Immunoglobulin receptor • Membrane-bound antibody (mIg) on B cell determines B cell specificity • Secreted antibody (sIg) differs in the carboxyl-terminal domain • mIg has three additional regions • extracellular hydrophilic sequence • hydrophobic transmembrane sequence • short cytoplasmic sequence Ig

  3. mIg • All five Ig classes can be expressed as mIg • occurs at different developmental stages • immature cell expresses only sIgM • mIgD appears later in maturation • memory cells express a variety of isotypes • Genetic mechanisms are responsible for expression of a particular mIg • B cell receptor indicated by BCR

  4. BCR • The tail of the BCR is too short to signal • through tyrosine kinases and G proteins • Recently shown that BCR has other parts • a heterodimer called Ig-a/Ig-b • two molecules associate with one mIg • both Ig-a and Ig-b have long cytoplasmic tails • both contain tyrosine residues that can be phosphorylated by tyrosine kinases

  5. Antigenic determinants on Ig • Antibodies are glycoproteins • Therefore, will serve as immunogens • Epitopes on the Ig fall into three categories: • isotypic • allotypic • idiotypic • Epitopes located in characteristic positions

  6. Immunoglobulin isotypes • IgG • most abundant type • IgM • pentamer • IgA • secretory Ig • IgE • causes hypersensitivity • IgD

  7. Immunoglobulin superfamily • Heavy and light chains share characteristics • Common evolutionary ancestry possible? • all have the immunoglobulin-fold domain • perhaps the genes encoding them arose from a common primordial gene • Many membrane proteins have structures similar; did they come from the same gene? • Classified as immunoglobulin superfamily

  8. Members of the superfamily • Part of the BCR • Poly-Ig receptor (for secretion) • T-cell receptor • CD2, CD4, CD8, CD 28 and part of CD3 • Class I and II molecules • Cell-adhesion molecules • Others

  9. Monoclonal antibodies • Produced by fusing an antibody-producing plasma cell with a myeloma cell • produces a hybridoma • possess immortal character of the myeloma • and the antibody-synthesizing capacity of the B cell

  10. Assignment • Read Chapter 6, Antigen-Antibody Interactions • Review question 6 (pg 163)

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