Lec6 Antigen recognition Flashcards Preview

Immunology > Lec6 Antigen recognition > Flashcards

Flashcards in Lec6 Antigen recognition Deck (27):

Features of antibodies

- 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


Features of T cell receptors

- 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


B cell receptor structure

- 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


Complementary determining region [CDR] [function, where is it location]

- 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


T cell receptor structure

- one variable domain, one constant domain - one B and one a chain - binds linear protein epitope presented on MHC


T and B cell maturation

- 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


Somatic recombination

- 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


Junctional diversity

- 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


Sequence of rearrangement for Ig?

- D-J in heavy chain rearranged, then V - if successful: light chain rearranges - if both succesful: other chromosome rerrangement prevented


Processes for diversity generation

- combinatorial diversity [somatic recombination[ - junctional diversity - any heavy chain can associated with any light chain


IgA [function]

mucosal immunity


IgD function

on naive b cells no effector function


IgE function

1. mast cell activation [immediate hypersensitivity] 2. defense against helminthic parasites


IgG Function

1. opsonization 2. complement activation 3. antibody-dependent cell mediated cytotoxicity 4. neonatal immunity 5. feedback inhibition of B cells


IgM function

1. naive b cell antigen receptor 2. complement activation


Are there more types of b cells or t cells?

T cells


Does pre-B/T cell express antigen receptor?

yes - one chain of antigen receptor


Does immature B/T cells express antigen receptor?

yes - complete receptor


Does immunoglobulin or TCR get change in constant region?

- Ig does: get heavy chain class switching from membrane to secretory Ig - TCR does not


Does Ig or TCR have higher affinity

Ig higher affinity Ig affinity increases during immune rxn TCR has no change


Which MHC does CD4 recognize?

class II MHC


Which T cell recognizes MHC 1?



What is order of recombination [in V,D,J]

- D-J in heavy chain rearranges first - Then V in heavy chain rearranges - Then light chain rearranges


Heavy chain has which things ?

VDJ Part of variable region of Ig


beta chain has which things?

VDJ Part of variable region of TCR


light chain has which things? What two kinds of light chain?

has VJ lambda and kappa light chains Part of variable region of Ig


alpha chain has which things?

VJ Part of variable region of TCR