Immunology 3- Pathogenicity and the host reponse Flashcards
What is adaptive humoral immunity?
The form of adaptive immunity that is mediated by B lymphocytes.
B cells can produce 5 different antibody isotypes, what are they?
IgM, IgD, IgG, IgE and IgA.
different isotypes have different constant regions of their heavy chains
B cells SWITCH ISOTYPES after interactions with t helper cells.
B cells also have 2 different types of light chain, lambda and kappa
Whats the function of IgD?
Function obscure, in mice that lack IgD, they have no apparent phenotype
Is really only found on the receptor of naive B cells.
We find very little IgD in the serum (not secreted)
What is the function and structure of IgM?
Igm–> first antibody you detect after infection
- it forms pentamers, hexamers very rare
A protein called the J chain, holds 5 different IgM anitbodies together in this pentamers
- IgM receptors of naive B cells
-Low affinity, high avidity, fixes complement.
Which B cell isotypes has two subclasses?
IgA (IgA 1 and IgA 2)
what is the first antibody to be secreted in the adaptive immune response?
IgM
Which B cell isotype has 4 subclasses and plays a role in neonatal immunity?
IgG
Which B cell isotype(s) can activate complement ?
IgM and IgG (classical pathway)
Which B cell isotype causes allergy?
IgE
What does antibody IgE interact with and do?
Interacts with mast cells, eosinophils and basophils. IgE is specialised to fight helminths
Phases of the humoral immune response
- If no T cell help, which antibody isotype is produced?
- With T cell help, which antibody isotypes can this (the above) antibody isotype switch to?
- Under what circumstances and which antibody isotypes does affinity maturation occur?
- IgM is produced if no T cell help
- IgG, IgA and IgE produced with T cell help
- Affinity maturation usually occurs in IgG, IgA, IgE and it needs T cell help.
What drives isotype switching?
T cell cytokines
What is the default isotype?
IgM (without T cell help and cytokines, B cells will produce IgM)
Which cytokines drives isotype switching to IgG?
IFN-gamma
Which cytokine drives isotype switching to IgE
IL-4
Which cytokine drives IgA differentiation
TNF-beta
How does herpes simplex virus (HSV) interfere with antigen processing process?
- Inhibition of antigen presentation, HSV interferes with TAP transporter. so it interferes with the transport of peptides from the cytoplasm to ER.
How does the Epstein-Barr virus (EBV) interfere with antigen presentation process ?
- Inhibition of proteasomal activity
How does cytomegalovirus (CMV) inhibit antigen processing and presentation?
- inhibits proteasomal activity
- removes MHC class I molecules from the ER.
CTLs generally require help from TH1 cells
what do TH1 cells do
Okay, we know TH1 cells secrete IFN-gamma, makes macrophages superb phagocytes.
The TH1 cytokines IFN-gamma and IL-12 promote CTL differentiation. - important for maturation of cytotoxic T cells, they help turn a CD8 T cell into a cytotoxic T cell
CTLs will also secrete IFN-gamma which in turn promotes TH1
TH1 cytokines promote IgG isotype (opsonisation) switching.
In the mucosa which isotype antibody is important?
IgA
In the blood, which isotype is important?
IgG
Which bacteria multiply within macrophages
Mycobacterium leprae, mycobaterium tuberculosis, listeria monocytogenes
Which bacteria are non-invasive (extracellular) and multiply in the bodies’ fluids?
Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa.
Which bacteria cause disease almost exclusively by the release of toxins?
Vibrio cholerae, Corynebacterium diptheriae, Bordetella pertussis, Bacillus anthracis
Can antibodies penetrate cell membranes?
NO, ANTIBODIES CAN’T PENETRATE CELLS MEMBRANES (humoral immunity tends to be irrelveant for obligate intraacellular organisms)
TH1 AND CTL CELLS
