4/04 Flashcards
How can we fully activate a CD8 cell?
1- the APC contact the T helper and the CD8
2- helper and APC release IL2 for proliferation, IL12 and interferon for the granules enzymes, IL7 for survival and IL21 for generation of memory
What can a completely active CD8 cell do?
It can express T-bet and eomesodermin causing the production of interferon gamma, perforin and granzyme B to kill the pathogen or perform the kiss of death
What’s the kiss of death?
thanks to FAS ligand-FAS interaction or TNF α-TNF receptors interaction there’s a lose contact between the lymphocyte and the target and the latter will die because of the release of perforin and granzyme
Why a T lymphocyte do not undergo apoptosis in presence of apoptotic molecules?
Because lymphocytes membrane is protected by cathepsin
Against which kind of pathogen are CD8 lymphocytes particularly active?
virus and intracellular bacteria
Starting from a Th0 CD4+, how can we obtain a Th1 or a Th2 T cell?
INF-gamma -> block of GATA3 -> Th1
IL4, IL5, IL13 -> block of T-bet -> Th2
Which are the effects of the activation of a Th1 cell?
Th1 secrete INF gamma, INFalfa and IL2 causing the activation of pro-inflammatory macrophages, the expression of MHCclassII, the stimulation of NK and CD8 cells.
This happens expecially against bacteria
Which is the target of Th2 cells and why?
They target worms and parasites secreting IL4, IL5, IL9, IL13 causing a IgE and IgA response, anti-inflammatory macrophages activation and stimulation of eosinophils
Which is the main target of Th17 cells?
They mostly act against fungi or extracellular bacteria
How can we obtain a Tfh cell starting from a Th0?
APC secret IL6 and ICOS-Ligand, The T cells express the ICOS receptor and this binding cause the expression of CCR7 or CXCR6
What’s the role of follicular T cells?
Follicular T cell are necessary for the collaboration between B and T cells in the lymphatic organ: they may express CCR7 and be attracted in the T cell area, or they may express CXCR6 and move towards the B cell area. In both cases they follow cytokines’ gradients.
When a follicular T cell enter the B cell area, it can contact B cells (thanks to ICOS ligands) and activate them.
TFh also release IL21, necessary for the proliferation of B cells.
What are the microfold cells?
M cells are cells present in between enterocytes, intestinal cells and mucosa cells. They allow the antigen to enter without any damage to the anatomical barrier (transcytosis)
How happens the T dependent B cells activation?
Which B cell affect?
T helper express CD40ligans which binds CD40 (receptor) present on B cells. This bound cause the expression of the AID enzyme (activation-induced deaminase) that then:
- Induces the survival signals to the B cell
- Induces all the germinal centre reaction
- Allow the production of different kind of antibodies
- Induces the affinity maturation of the BCR: increases the variable portion of the BCR
- Induces the differentiation and the survival of memory B cells
T dependent B cells activation: type of cell affected, type of antigen used, antibodies produced and type of plasma cells obtained?
B2 follicular cells
protein antigen
IgE, A, G
long live plasma cells
T independent B cells activation: type of cell affected, type of antigen used, antibodies produced and type of plasma cells obtained?
B1 cells or marginal zone B2 cells
polysaccharide or lipidic antiged
IgM
Short live plasma cells