pre-IC2 Antibodies Vs T cell receptor Flashcards
Cellular & humoural components of innate Vs adaptive immunity
Innate:
Cellular - phagocytes (macrophages, neutrophils), dendritic cells, NK cells & mast cells
Humoural - complement proteins & cytokines
Adaptive:
Cellular - B & T cells
Humoural - cytokines & antibodies
Structure of Ab
- Label heavy & light chains
- Label constant & variable regions
Check eL slide
Which region has CDR?
Fab region
Which region has CDR?
Fab region
How many CDRs per Ab?
3 CDRs found within each light and heavy chain of variable region of Fab -> total 12 CDRs found per Ab
Significance of CDR
- Responsible for diversity of antigen specificities of Ab produced by mature B cells
- For each Fab arm, aa within variable domain of both light & heavy chains are non-consecutively arranged to form 3 CDRs
- CDRs bind to epitope of antigen
What forms a paratope?
1 Vh + 1 Vl -> 6 CDRs
Binding of Fab vs Fc regions of Ab?
- Fab binds to antigen of pathogen
- Fc region binds to effector cells e.g. neutrophils, NK cells & macrophages + complement proteins
Structure of TCR + label
Check eL slide
Significance of CD3 proteins
CD3 proteins facilitate signal transduction for T cell activation
What are the various CD3 proteins?
CD3e, CD3z, CD3s, CD3y
What does ITAM stand for?
Immunoreceptor tyrosine-based activation motif
How many ITAMs do each CD3 possess?
CD3e, CD3s & CD3y: 1 ITAM each
CD3z: 3 ITAMs
How many ITAMs per TCR complex?
CD3zz: 6 ITAMs; CD3ey: 2 ITAMs; CD3es: 2 ITAMs
10 ITAMs per TCR
How does ITAM lead to T cell activation?
When antigen binds to T cell receptor, tyrosine residues in ITAM gets phosphorylated (i.e. post-translational modification) → initiates a series of downstream T cell signalling events → T cell activation
What gives rise to TCR diversity?
Genetic recombination of DNA segments in genes encoding variable regions of alpha & beta chains → Va chain undergoes VJ recombination & Vb undergoes DJ, then VDJ recombination
TCR vs Ab
- TCR = half of Ab (one Fab arm) = 6 CDRs
- Variable domains in both TCR & Fab domain of Ab are antigen-binding sites
Where do T cells originate and travel to for development into T lymphocytes?
Originated from bone marrow, travel to thymus (primary lymphoid tissue)
Where do T cells originate and travel to for development into T lymphocytes?
Originated from bone marrow, travel to thymus (primary lymphoid tissue)
Where are T cells localised?
Secondary peripheral lymphoid tissue (lymph nodes, spleen)
Effector vs Memory T cells
Effector T cells die after combating with pathogen while memory T cells do not
Where did B cells originate, and where is it circulated?
Originated from bone marrow
Circulates through the blood & secondary peripheral lymphoid tissue
How are different B cell clones formed?
Progenitor B cells rearrange Ig genes resulting in immature B cells possessing a different aa sequence in the variable regions of surface Ig
What happens when B cells encounter pathogens?
Naive/ virgin B cells gets activated and becomes mature B cells which secrete IgM
What other processes are B cells involved in?
- Class switching: Genetic rearrangement of constant regions of Fc domain in IgM → Mature B cells now produce IgG
- Gene rearrangement of variable regions of Fab domain of IgG genes → Each B cell clones ends up a different hypervariable CDR
Antigen affinity vs Antibody specificity. What happens with low Ab specificity?
- Antigen affinity: strength of intx btw antigen & paratope
- Ab specificity: Goodness of fit btw antigen & paratope → Low Ab specificity: Ab binds to more than 1 epitope AKA cross-reactivity
Affinity vs avidity
- Affinity: Strength of intx btw paratope & antigen @ 1 antigenic site
- Avidity: Strength with which Ab binds to its target (target has multiple antigenic sites)
