Immunology Chapter 11 • Richard L. Myers, Ph.D. • Department of Biology • Southwest Missouri State • Temple Hall 227 • Telephone: 417-836-5307 • Email: [email protected]
Dec 14, 2015
ImmunologyChapter 11
• Richard L. Myers, Ph.D.
• Department of Biology
• Southwest Missouri State
• Temple Hall 227
• Telephone: 417-836-5307
• Email: [email protected]
T cell receptor
• Nature of the T cell receptor (TCR) recently discovered
• T cell receptor is a cell-surface molecule
• TCR is not specific for antigen alone, but rather antigen in association with an MHC
• TCR studied with monoclonal antibodies and nucleic acid probes
Functional assays for TCR
• TH cells can be assayed by
– proliferation of TH cells
– secretion of various cytokines
– ability to activate TC or B cells
• TC cells can be assayed by
– lysis of target cells– secretion of cytokines
Structure of T cell receptor
• Experimental approaches assumed that there should be a significant difference in the TCR from clone to clone
• Kappler and Marrack – used clonotypic monoclonal antibodies– identified and isolated the TCR
• These researchers and others showed the molecule is composed of an and chain
• TCR is a heterodimer• Contains and chains• Constant and variable
regions• Identified and chains
– 2 - 5% of all T cells
• Very similar to antibody• Variation in amino
terminal end
Organization and rearrangement of TCR genes
• The and TCRs are expressed only in T cells
• The genes for these are very similar to the multigene organization of the Ig genes
• Separate V, D, and J gene segments rearrange during T cell maturation
• Genes composed of introns and exons
• Rearrangements produce more antigenic specificities than antibodies
T cell receptor complex• The TCR associates with CD3
– forms a TCR-CD3 membrane complex
• The CD3 (accessory molecule) is involved in signal transduction after seeing antigen
• CD3 is a complex of 5 invariant chains that form heterodimers– gamma and epsilon chains ()– delta and epsilon chains ()– two zeta chains ()– zeta and eta chains ()
• TCR heterodimer determines binding specificity
• The CD3 dimers are required for– expression of the
TCR
– signal transduction
• The and are members of Ig superfamily
• Both and are different
T cell accessory membrane molecules
• Recognition of an antigen-MHC complex is mediated by the TCR-CD3 complex
• A variety of accessory membrane molecules play a role in recognition and activation– many are adhesion molecules– strengthen the interaction between the two cells– transduce signals through the membrane– some are members of the Ig superfamily
• T cells possess several molecules– CD2
– LFA
– others
• These bind to ligands on APCs or target cells
• Strengthen the association between these cells
CD4 and CD8 coreceptors
• Both CD4 and CD8 play an dual function– adhesion molecules– co-signaling receptors
• CD4+ T cells recognize antigen with class II MHC molecules
• CD8+ T cells recognize antigen with class I MCH molecules
• CD4 is a 55 kDa monomeric membrane glycoprotein– has 4 extracellular domains
• CD8 is a disulfide-linked heterodimer– both are small glycoproteins of approximately
30 - 38 kDa
• CD4 binds to the 2 domain of class II
• CD8 binds to the of a class I
• They react with the same MHC molecule that reacts with the TCR