Immunology Chapter 4
Adaptive Immune System Learning Objectives
1. How do the recognition capabilities of B and T lymphocytest differ?
 B lymphocytes are able to recognize the conformations of proteins, lipids, carbohydrates, and
nucleic acids, all in their native form
 T cell receptors (TCRs) only recognize peptides displayed by APCs (MHC restriction)
2. Where is the greatest variability concentrated in antibodies and TCRs?
 The CDR regions have the greatest variability (aka. hypervariable/compentarity-determining)
 Of these, the CDR3 region at the junction of the variable and constant region has the most
variability. Don’t confuse this with one of the proteins that mediates signaling in the cell
3. What’s another name for antibodies?
 Ig (immunoglobin)
4. What are immunoglobins/antibodies named after?
 Igs are named after their heavy chains (α, δ, ε, γ, or μ)
5. When secreted from a B cell, which antibodies exist as monomers?
 IgE and IgG are monomers, IgA is a dimer, and IgM is a pentamer
Think: EGg MONOzygotic
AM unique
6.
Do antibodies need to exactly match their antigen?
 No, cross reaction can occur with similar epitopes (recognizable chunks)
7.
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What is the structure of TCRs? What molecules allow them to signal binding?
TCRs have one beta and one alpha chain, connected by sulfide linkages
Proteins CD3 and ζ in combination with the T Cell Receptor form the TCR complex, which can
exert intracellular effects
i. In addition, CD4 or CD8 molecules also transmit activating signals
8. Positive and negative selection
 k
9. Where are joining and diversity gene segments located? What happens to them?
 Joining (J) and Diversity (D) segments are located between Variable (V) gene segments
 They are recombined by VDJ recombinase, which is composed of RAG proteins 1&2
(Combinational diversity)
10. How is Junctional diversity produced?
 Removal of random nucleotides from V, D, and J segments (by exonuclease)
 Addition of random nucleotides (by terminal deoxyribonucleotidyl transferase)
 Overhanging DNA sequences can be generated (filled in by “P-nucleotides”)
11. What are the two checkpoints for the maturation of B cells?
 1st: assembly of μ chain and surrogate light chain with Igα and Igβ signalling molecules

2nd: formation of complete IgM antigen receptor (light chain production)
12. What is the process of allelic exclusion?
 Allelic exclusion helps to make sure that each cell expresses only a single type of receptor
 The first expression of μ chains during antibody construction shuts off recombination of Ig
heavy chain genes on the second chromosome; same for light chains
 Likewise both α chain and β chain formation supress recombination of the second
chromosome TCR α/β chain locus
13. Which antigens does a mature B cell display?
 Mature B cells display both IgM and IgD
think: M.D.
14. What is the first two checkpoints for maturation in T cells? Any more?
 Formation of β chain as part of the future TCR receptor
 Formation of α chain
 The last stage is positive/negative selection/“death by neglect”
Boobs Ass and Pussy are Never Dishonest
IL-7