L3. Recognition of antigen Flashcards
where do b cells and t cells differentiate
both originate in bone marrow
- B cells diff in bone marrow
- T cells diff in thymus
what are BCRs and TCRs
the receptors on surface - recognise foreign moelcules
2 main functions of antibodies
bind foregin antigens
mediate effector functions to neurtralise/eliminate foreign invaders
what enzyme can cleave the disulphide bond linking the heavy chains
papain
Fab
Fragment antigen binding
Fc
fragment crystalizable
what does hinge region allow for
slight shape change
what does the antibody recognise
antigenic epitope
what is hypervariable region on antibody also known as
complementary determining region
2 types of epitopes
linear and conformational
conformational more commone
what type of forces involved in antigen antibody binding
non-covalent
affinity def
strength of bidning between epitope and antibody antigen binding site
avidity def
overall stergnth of antibody antigen complex eg if its using both bidning sites
Fc portion of antibody
Fc portions is responsible for its biological activity
e.g. the effector stuff
4 main effector functions of ABs
neutralisation
opsonisation
activation of complement
ADCCn
neutralisation
- antibodies prevent pathogen from binding target
- important in viruses: prevents them getting into cell
- many vaccines elicit this response
opsonisation
ABs target the pathogen for phagocytosis
- Fc domain on AB binds to Fc receptor on antigen
Complement activation
the AB activates the complement system:
- formation of pores in bacterium
- or induce phagocytosis again
ADCC
Antibody dependent cell mediated cytotoxicity
- so cells express viral proteins in membrane after being infected, and ABs bind to this
- mediates extracellular killing of the cell
what Fc receptor is on NK cells
FcyRIIIa
what do antibody classes depend on
C region used by heavy chain
diff antibody classes
IgG
IgM
IgD
IgA1
IgE
IgG
most abundant
4 types
IgG1 most common
IgM
earliest antibody made after Ag contact
pentamer
up to 10 bidning sites
