Antigen-Antibody, B-Cell Receptors of B lymphocytes in adaptive immunity Flashcards
(20 cards)
What is considered humoral and what is considered cell-mediated in adaptive immunity?
B- Humoral
T- Cell mediated
How does adaptive immunity recognize foreign substances?
B and T cells generate receptors (BCR, TCR) which bind to foreign
What does BCR contain? What does TCR contain?
BCR - antibody of defined specificity
TCR - specific for PEPTIDES from APC degraded on MHC molecules
What is membrane bound form of an antibody?
Ig(alpha) + Ig(beta) next to a cytosolic segment + hydroPHOBIC segment + spacer
What chains does a BCR contain? How does this affect the specificity?
Quarternary protein
2 identical heavy, 2 identical light
The interaction of heavy + light determines the specificity for antigents
What do Iga and IgB do in BCR?
Transduce signals via ITAMS
What are the two TCR types? What are they structurally similar to?
αB and γδ
Structurally similar to immunoglobulin domains
What two regions does αB contain? what does it bind?
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
Where are peptide sources from?
Endo/exo processed antigens
What is a ligand? What does it cause?
Receptor binding that causes change (dimer or multimer) -> lipid rafts-> cascade
What starts the signaling intracellularly? Why?
Tyrosine phosphorylation
Serves as a docking spot for adaptor molecules
What are phopshorylated on ITAMS?
CD3 (T cells) and Igα/B (B cells)
What is the immune system activated by in a pathogen?
Carbohydrate -> polysaccharides of bacterial cell wall
Lipids -> glycolipids
Nucleic acids -> autoimmune disease
Proteins -> complex
What are the three requirements for immunogenicity?
Foreign
Size > MW of 6000 daltons
Complex
Time of exposure
How do small molecules interact with big molecules?
Small molecules attach to big, which are the carrier proteins
Small molecules are the antigenic determinants on carrier molecule
What is the structure of a typical antibody molecule?
2 light, 2 heavy held by DISULPHIDE BONDS w/ domains
H chains held by interchain disulphide bonds in proline HINGE region
What are the two light chains? The 5 heavy chains? What determines the group?
Light- Kappa / Lambda
Heavy - Mu/Gamma/Alpha/Delta/Epsilon
*Grouped depending on what H chain is used
What are the constrain domains? The variable?
Variable: VL, VH
Constant: CL, CH1, CH2, CH3 *the heavy base doesn’t change, just the variable L/H at the top)
What is the structure of a typical antibody molecule IgG?
N terminal (Antigen binding site) FAB C terminal (Fc =crystalisation) mediates effector
What do antigens bind to?
FAB fragment
anti- the antigen
