https://padlet.com/ho_phui_san2/A231P5 en-us 2021-05-17 09:50:53 UTC 2021-05-25 03:14:04 UTC hello@padlet.com https://padlet.com/ho_phui_san2/A231P5/wish/1556012515 Activation of T cells involve in TCR present on the T cell surfaces recognizing antigen that is presented on MHC by phagocytes.

2 classes of MHC
MHC class 1 present on other cells
MHC class 2 present on phagocytes]]> 2021-05-25 02:24:08 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556012515 https://padlet.com/ho_phui_san2/A231P5/wish/1556012750 1) CD4+ is helper T cell while CD8+ is cytotoxic T cell. 
2) Dendritic cells activate Naive T cells ]]> 2021-05-25 02:24:14 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556012750 https://padlet.com/ho_phui_san2/A231P5/wish/1556012772 glycoproteins
CD4- Th cell ->Th1, Th2, Tfh, Treg, memory Th Cell
CD8- Tc cell-> memory Tc cell, effector Tc cells
(TCR:alpha & beta subunits/ gamma delta subunits)

Co-stimulation
CD28 -APCs to B7-1/B7-2 - resting Tcell

MHC
-CLASS I -(3 alpha and 1 beta) endogenous, ER (all nucleated cell)
-CLASS II - (2 alpha and 2 beta) exogenous, specialised vesicular compartment]]> 2021-05-25 02:24:14 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556012772 https://padlet.com/ho_phui_san2/A231P5/wish/1556012893 1.Antigen-presenting cells goes through Antigen Processing and Presentation to Naive T-Cells to activate them

2. T-Cell receptors and CD4 in a CD4+ T-Cells binds to the presented antigen fragment to start the activation of T-Cells]]> 2021-05-25 02:24:17 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556012893 200192281 https://padlet.com/ho_phui_san2/A231P5/wish/1556012974 T cell activation is a 2 signal process 
1. Recognition and binding by TCR and CD4+ generated the first signal of T cell activation 
2. Costimulation which enhances the 1st signal. Without costimulation, T cells which recognised the antigen remain in prolonged state of inactivity 
Costimulators include cytokines and pair of plasma membrane molecules. An example is B7(found on APC) and CD28 (found on T cell) 

2 types of MHC 
- MHC 2 present to CD4
-MHC 1 present to CS8]]> 2021-05-25 02:24:19 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556012974 ngfae123 https://padlet.com/ho_phui_san2/A231P5/wish/1556013053 2 signals are required to fully activate T cells.

1) TCR recognizes and binds the antigen & CD4+ receptor and binds to MHC II molecule which generates the first signal.

2) T-cell costimulation
- cytokines
- pair of plasma molecules

Without 2nd signal, T cells that previously recognize antigen will remain inactive.

For CD8+, it binds to MHC I molecule.]]> 2021-05-25 02:24:21 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013053 https://padlet.com/ho_phui_san2/A231P5/wish/1556013107 T cells can differentiate into Helper or Killer T cells]]> 2021-05-25 02:24:22 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013107 https://padlet.com/ho_phui_san2/A231P5/wish/1556013128 The structure of T cell receptor structure (alpha and Beta chains) : Made up of 2 polypeptide chains that will compose on antigen binding site together.
 and it undergoes activation ]]> 2021-05-25 02:24:22 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013128 https://padlet.com/ho_phui_san2/A231P5/wish/1556013195 T-cell activation requires 2 signals. 
1st signal: recognition and binding of TCR to the antigen presented
2nd signal: co-stimulation  (B7---- CD28)]]> 2021-05-25 02:24:24 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013195 https://padlet.com/ho_phui_san2/A231P5/wish/1556013254 T cells undergoes activation and differentiation and they are CD4+ and CD8+ 

The activation of naïve T cells requires 2 signals. The first signal is when the TCR recognizes and binds to the MHC 2 molecule (CD4+) or the MHC 1 molecule (CD8+) 
The second signal is co-stimulation, and some common ones are CD28 and CD45 ]]> 2021-05-25 02:24:25 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013254 https://padlet.com/ho_phui_san2/A231P5/wish/1556013326 Two subsets of T cells: CD4+ & CD8+ 
Two signal required for activation of T cells : TCR and costimulation
Antigen presenting cell(APC) such as dendritic cells, macrophages & B cells present peptide antigen on MHC to naive T cells at lymph nodes

]]> 2021-05-25 02:24:27 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013326 https://padlet.com/ho_phui_san2/A231P5/wish/1556013591 After DCs process the pathogen, they will present the antigen on its MHC, for recognition by T cells. 
There are two types of MHC Classes: MHC Class I and MHC Class II
Two main types of T cells: 
(Killer) Cytotoxic T cells and Helper T cells]]> 2021-05-25 02:24:33 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013591 20033646_2 https://padlet.com/ho_phui_san2/A231P5/wish/1556013857 T cell receptors is used for antigen binding. T cells can be divided into helper T cells (CD4) and cytotoxic T cell (CD8). 

]]> 2021-05-25 02:24:40 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556013857 https://padlet.com/ho_phui_san2/A231P5/wish/1556014134 Helper T cells and cytotoxic t-cells.
Co-receptors are
CD-4 for helper 
CD-8 for cytotoxic
They are activated by processed antigens presented on Antigen Presenting Cells.

]]> 2021-05-25 02:24:46 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556014134 https://padlet.com/ho_phui_san2/A231P5/wish/1556014236 Dendritic cells activate naïve T cells through presenting the pathogen to the lymph nodes. There are two types of T cells, cytotoxic and helper. Each of it has an effector and memory. ]]> 2021-05-25 02:24:49 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556014236 https://padlet.com/ho_phui_san2/A231P5/wish/1556014340 There are 2 signal process requires for T cell activation. First is the recognition and binding by TCR and CD4. Second is co-stimulation includes cytokines and other co-stimulator. The most important pair are B7 and CD28. The 2 signals activate T cells in which T cells synthesize and secretes cytokines IL-2.]]> 2021-05-25 02:24:51 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556014340 https://padlet.com/ho_phui_san2/A231P5/wish/1556014412 Peptide fragments present on the MHC complex of the antigen presenting cell will bind to the T cell receptor of the naive T cell and helper T cell and effector T cell, causing the activation of these T cells.MHC II helps to activate CD8 cells while MHC I helps to activate CD4 cells]]> 2021-05-25 02:24:53 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556014412 Pengiunieee https://padlet.com/ho_phui_san2/A231P5/wish/1556014597 2 classes of MHC (class I and II) 
class I is found in all cell except RBC
class II is found in antigen presenting cells

 ]]> 2021-05-25 02:24:57 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556014597 200042541 https://padlet.com/ho_phui_san2/A231P5/wish/1556014691 t cells have t cell receptors on cell membranes, which is used for antigen binding. t cells can be divited to 2 classes, CD4 and CD8]]> 2021-05-25 02:24:59 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556014691 20026204_2 https://padlet.com/ho_phui_san2/A231P5/wish/1556016262 2 different types of naive T cells
--> CD4+ and CD8+
each of these 2 T cells have different signals for activation]]> 2021-05-25 02:25:33 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556016262 https://padlet.com/ho_phui_san2/A231P5/wish/1556016400 T cells are activated when presented with MHC class molecules. Once T cells are activated they release cytokines]]> 2021-05-25 02:25:36 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556016400 https://padlet.com/ho_phui_san2/A231P5/wish/1556016614 T cell is activated depends on: 
Class I MHC (bound by TCR on CD8+)
Class II MHC (bound by TCR on CD4+ T cells)]]> 2021-05-25 02:25:41 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556016614 https://padlet.com/ho_phui_san2/A231P5/wish/1556017857 TC kills infected cells (or tumour cells) through secretion of perforin and granzymes or activation of death receptor. Requires participation of TH and cytokines to generate large pool of memory TC]]> 2021-05-25 02:26:08 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556017857 https://padlet.com/ho_phui_san2/A231P5/wish/1556019295 T-cells require activation to carry out their function effectively. 
e.g. activation of naive CD4+ T cell by antigen presenting cell]]> 2021-05-25 02:26:39 UTC https://padlet.com/ho_phui_san2/A231P5/wish/1556019295