CH 5: Antigen Recognition by T Cells

Question 1

Never have T cell activation w/o?

Answer 1

Antigen Presenting Cells

Question 2

Professional APCs

Answer 2

• DCs
• Macrophages
• B cells
• MHC II

Question 3

MHC II

Answer 3

Helper T cell activation
- secrete cytokines

Question 4

MHC I

Answer 4

Cytotoxic T cell after viral infection

Question 5

CD4 + _____

Answer 5

MHC II

Question 6

CD8 + _____

Answer 6

MHC I

Question 7

TCR binds to?

Answer 7

MHC (I/II) & Peptide

Question 8

Signal 1

Answer 8

TCR + Peptide + MHC (I/II) + CD4/CD8 co-receptor

Question 9

Signal 2

Answer 9

CD28 interaction with B7

Question 10

T cells vs B cells: Similarities

Answer 10

TCR and Immunoglobulins similar structure, gene rearrangement, very diverse, specific for one antigen

Question 11

T cells vs B cells: Differences

Answer 11

• Igs - bind epitopes on intact molecules present on microbe surface; TCRs - recognize peptide antigens from pathogen + MHC on cell surface
• Ig mem-bound or secreted; TCRS always mem-bound
• Ig - somatic hypermutation of antigen-binding site and isotype switching; TCRs - no change after antigen binding
• Ig - recognize antigen + mediate effector functions; TCR - only recognize antigen

Question 12

TCR looks like?

Answer 12

Single fab fragment of IgG

Question 13

2 polypeptide chains

Answer 13

TCRalpha & TCRbeta
- each has V region, C region, transmembrane region and cytoplasmic tail
- each has amino-terminal V domain, C domain, and mem-anchoring domain
- antigen-recognition site formed by V alpha and V beta domains
— sequence variation in 3 regions of hypervariability/CDRs

Question 14

Alpha-chain locus

Answer 14

chrom 14

Question 15

Beta-chain locus

Answer 15

chrom 7

Question 16

Gene segments like that of Immunoglobulin

Answer 16

• 1 C alpha gene, 2 C beta genes
• rearrangement in thymus
• gene segments flanked by RSSs
• RAG complex and DNA-modifying enzymes
• P and N nucleotides inserted

Question 17

V(D)J recombination

Answer 17

Mechanism of gene rearrangement in B and T cells
- results in clonal diversity in antigen receptors
- RAG recombinase - made only in lymphocytes
— specific to adaptive immunity
- RAG genes lack introns - likely developed early in evolution of adaptive immunity

Question 18

TCR expression: Final alpha-chain and beta-chain genes have exons encoding?

Answer 18

• leader peptide
• V region
• C region
• Membrane-spanning region

Question 19

Alpha and beta chains enter _____ to form ______?

Answer 19

ER and pair to form alpha:beta TCR