3/04 Flashcards
Which types of B cells can we obtain after the maturation process? Which antibodies present on their surface?
B1 cells: IgMhigh and IgDnull
Marginal zone B cells: IgMhigh and IgDnull
Follicular B2 cells: IgMhigh and IgDhigh
What’s the role of marginal zone B cells?
These B cells are activated by the interaction between the notch signal and the delta ligand, they express CD1 that bind glycolipidic antigens and present them to invariant NKT cells and the complement receptor
What’s the SMAC?
It’s the supra molecular activation cluster: the close contact between the T cells and the APC thanks to integrins and addition molecules
Which signals can induce the activation of T cells
Increase in intracellular concnetration of calcium
PKC activation -> NfkB activation
G proteins that activate the MAP kinase
Which type of co-stimulatory signals are necessary to fully activate a T cell?
Ig-superfamily’s molecules able to bind CD28 and CTLA4,
TNF-superfamily’s molecules
Describe how Ig-superfamily’s molecules activate and regulate T cells
The CD28 (part of the Ig superfamily) on the T cells bind the B7 on APC.
This is expecially required by CD4 and regulatory T cells in comparison to CD8 and it’s not necessary for memory T cells.
This interaction (plus the MHC-TCR interaction) stimulate the expression of CD40
How long does it take to activate a T cell?
20-30 hours
Which mechanisms are involved in the shutdown of the immune response?
CTLA4 expression
Fas receptor
expansion of regulatory cells
elimination of tryptophan
secretion of anti-inflammatory cytokines
When is CTLA4 released? What does it do?
It’s released after the binding between TCR and HLA, it induce the expression of molecules with the ITIM motif that, when phosphorilated, cause the inibition of activator signals
What’s a superantigen?
These are antigen able to activate 5-20% of lymphocytes, they’re present in case of a persistent infection
