Antigen-Antibody, B-Cell Receptors of B lymphocytes in adaptive immunity

Question 1

What is considered humoral and what is considered cell-mediated in adaptive immunity?

Answer 1

B- Humoral

T- Cell mediated

Question 2

How does adaptive immunity recognize foreign substances?

Answer 2

B and T cells generate receptors (BCR, TCR) which bind to foreign

Question 3

What does BCR contain? What does TCR contain?

Answer 3

BCR - antibody of defined specificity

TCR - specific for PEPTIDES from APC degraded on MHC molecules

Question 4

What is membrane bound form of an antibody?

Answer 4

Ig(alpha) + Ig(beta) next to a cytosolic segment + hydroPHOBIC segment + spacer

Question 5

What chains does a BCR contain? How does this affect the specificity?

Answer 5

Quarternary protein
2 identical heavy, 2 identical light

The interaction of heavy + light determines the specificity for antigents

Question 6

What do Iga and IgB do in BCR?

Answer 6

Transduce signals via ITAMS

Question 7

What are the two TCR types? What are they structurally similar to?

Answer 7

αB and γδ

Structurally similar to immunoglobulin domains

Question 8

What two regions does αB contain? what does it bind?

Answer 8

Variable + constant regions

Variable = 3 CDRs forming peptide specific binding sites
Constant = contain transmembrane regions

Binds boh antigen derived peptide and MHC, which is peptide bound

Question 9

Where are peptide sources from?

Answer 9

Endo/exo processed antigens

Question 10

What is a ligand? What does it cause?

Answer 10

Receptor binding that causes change (dimer or multimer) -> lipid rafts-> cascade

Question 11

What starts the signaling intracellularly? Why?

Answer 11

Tyrosine phosphorylation

Serves as a docking spot for adaptor molecules

Question 12

What are phopshorylated on ITAMS?

Answer 12

CD3 (T cells) and Igα/B (B cells)

Question 13

What is the immune system activated by in a pathogen?

Answer 13

Carbohydrate -> polysaccharides of bacterial cell wall
Lipids -> glycolipids
Nucleic acids -> autoimmune disease
Proteins -> complex

Question 14

What are the three requirements for immunogenicity?

Answer 14

Foreign
Size > MW of 6000 daltons
Complex
Time of exposure

Question 15

How do small molecules interact with big molecules?

Answer 15

Small molecules attach to big, which are the carrier proteins

Small molecules are the antigenic determinants on carrier molecule

Question 16

What is the structure of a typical antibody molecule?

Answer 16

2 light, 2 heavy held by DISULPHIDE BONDS w/ domains

H chains held by interchain disulphide bonds in proline HINGE region

Question 17

What are the two light chains? The 5 heavy chains? What determines the group?

Answer 17

Light- Kappa / Lambda

Heavy - Mu/Gamma/Alpha/Delta/Epsilon

*Grouped depending on what H chain is used

Question 18

What are the constrain domains? The variable?

Answer 18

Variable: VL, VH
Constant: CL, CH1, CH2, CH3 *the heavy base doesn’t change, just the variable L/H at the top)

Question 19

What is the structure of a typical antibody molecule IgG?

Answer 19

N terminal (Antigen binding site) FAB
C terminal (Fc =crystalisation) mediates effector

Question 20

What do antigens bind to?

Answer 20

FAB fragment

anti- the antigen