Lec6 Antigen recognition Flashcards
1
Q
Features of antibodies
A
- recognize: macromolecules, small chemicals, conformational and linear epitopes - diversity: each clone has unique specificity - antigen recognition mediated by: V regions of heavy and light chains [CDRs] - signal function mediated by: proteins [Iga and IgB] associated with membrane Ig - effector function mediated by constant C region of secreted Ig - get changes in constant region in secretion and in class-switching - fast on-rate, variable off-rate - higher affinity for antigen than TCR
2
Q
Features of T cell receptors
A
- recognize: linear epitopes, peptides displayed by MHC molecule on APCs - diversity: each clone has unique specificity [more diverse than Ig] - antigen recognition mediated by: variable regions [CDRs] of a and B chains - signal function mediated by: proteins [CD3] associated with TCR - no effector function - no changes in constant region - no change in affinity for antigen in immune response - slow on-rate, slow off-rate
3
Q
B cell receptor structure
A
- B cell receptor = membrane bound Ig - 2 heavy chains, 2 light chains attached into monomer with 2 binding sites - 2 types of light chains exist but never mixed on same antibody - can bind antibody molec in their native conformation
4
Q
Complementary determining region [CDR] [function, where is it location]
A
- 3 In each of light and heavy V domains of antibody and in each of Va and Vb in TCR - hypervariable domains - function like fingers to interact with antigens
5
Q
T cell receptor structure
A
- one variable domain, one constant domain - one B and one a chain - binds linear protein epitope presented on MHC
6
Q
T and B cell maturation
A
- common lymphoid progenitor - pre B or T cell expresses one chain of antigen receptor - immature cell expresses complete antigen receptor - then undergoes positive selection for receptors with weak antigen recognition [negative for those with high affinity] to get mature cell
7
Q
Somatic recombination
A
- responsible for generation diversity in both B and T cells - V-D-J joining - Heavy and light [or alpha and Beta in T cells] BOTH rearrange to get diversity
8
Q
Junctional diversity
A
- often gene segments to not align properly - gaps filled by terminal deoxyribonucleotidyl transferase [TDT] - nucleotides also may be gained or lost in other ways - occurs in by B and T receptors
9
Q
Sequence of rearrangement for Ig?
A
- D-J in heavy chain rearranged, then V - if successful: light chain rearranges - if both succesful: other chromosome rerrangement prevented
10
Q
Processes for diversity generation
A
- combinatorial diversity [somatic recombination[ - junctional diversity - any heavy chain can associated with any light chain
11
Q
IgA [function]
A
mucosal immunity
12
Q
IgD function
A
on naive b cells no effector function
13
Q
IgE function
A
- mast cell activation [immediate hypersensitivity] 2. defense against helminthic parasites
14
Q
IgG Function
A
- opsonization 2. complement activation 3. antibody-dependent cell mediated cytotoxicity 4. neonatal immunity 5. feedback inhibition of B cells
15
Q
IgM function
A
- naive b cell antigen receptor 2. complement activation
