1. 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

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

5. 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

6. 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-  /Ig-  –two molecules associate with one mIg –both Ig-  and Ig-  have long cytoplasmic tails –both contain tyrosine residues that can be phosphorylated by tyrosine kinases

8. 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

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

19. 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

20. 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

21. 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

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