Session 7 - adaptive immunity part 2 Flashcards
Impaired thymus development will affect the function of which lymphocytes?
T-cells and B-cells
B-cells are activated by T cells
What is the TCR made up of?
- T Cell Receptor: 2 chains (alpha and beta)
- CD3 complex co-receptor
(4 chains) - accessory molecule CD4/8
What are the three signals which fully activate the naïve T lymphocyte?
1) TCR binding antigen in MHC
2) CD28 binding B7 on APC
3) cytokines from APC
Following activation, the naïve T cell differentiates into 1 of 4 types of T helper cell.
Name the types
Which one has an inhibitory effect on another?
TH1
TH2
TH17
T reg
T reg inhibits TH1 and TH2 to help regulate the immune system
Which T helper cell is most useful against intracellular pathogens?
What does it do?
TH1
- stimulates CD8+ cytotoxic cell differentiation
- produces cytokines which activate and recruit macrophages
- Induces class switching to IgG or IgA
What does TH17 do?
recruits and activates neutrophils
Which cytokine drives development of TH1 ?
Il-12
What kind of immunity is TH2 involved in?
Why?
Humoral immunity against extracellular pathogens
Major effect is on B-lymphocyte, inducing class switch to IgE
What does IgE do?
- Opsonises helminths and parasites
- stimulates mast cell degranulation
Which antibody is present in hypersensitivity reactions?
IgE (mast cell degranulation to release histamine)
What is cross presentation?
Ability of APC’s to present antigen/peptide on MHC 1 and MHC 2, thus activating naïve CD8+ and CD4+ T lymphocytes
How do TH1 lymphocytes stimulate the differentiation of cytotoxic T cells?
- TH1 releases cytokines which causes differentiation of the CD8+ effector cell into CTL (cytotoxic lymphocyte)
Naïve CD8+ cells are activated by?
What do they differentiate into?
Recognition of MHC
Effector CD8+ cells* /
Memory CD8+ cells
*(can become CTL)
What makes up the variable region of the BCR?
distal ends of the heavy and light chains
What limits the amount of antigens we can recognise and mount immune response against?
Our determined set of MHC molecules
bc the combinatorial diversity of TCR’s and BCR’s is very high
Which 3 signals activate the B- cell?
1) BCR activation by antigen
2) T cell binding
(TCR/ MHC) and (CD28/ B7)
3) Cytokines and CD40 activation
How does a T-cell bind a B-cell?
(B cell presents antigen in MHC 2 complex)
- TCR binds MHC
- CD28 on T cell binds B7 on B cell
- CD40 ligand on the T cell activates CD40 on B-cell.
Which membrane protein is upregulated following BCR activation? (binding antigen)
B7 on the B cell
binds CD28 on T cell
What does CD40 activation induce?
Which cell facilitates this binding?
Heavy chain class switching from IgM
T helper cell (has CD40 ligand)
Which antibodies produced by B cells are thymus independent?
Only IgM
Other antibodies are generated by class switching stimulated by CD40 activation. T helper cells activate CD40
What is affinity maturation of the B-cell antibody response?
What does IgM look like?
Repeated exposure to the antigen can enhance the antibody’s affinity for it
Star shaped pentamer of antibodies
Benefits of the IgG response vs primary IgM?
Faster
Stronger
Lasts longer (antibodies stay in blood)
Higher affinity
What is IgA useful for?
IgM role?
Mucosal immunity
Activates complement
