T-cells, Effector Functions and MHC Flashcards
What are the X2 main types of T-cell?
What do each type do?
CD4 = can differentiate into different effector T-cell types
CD8 = are cytotoxic cells that kill target cells
What molecule is used by antigen presenting cells to present small fragment peptides of antigens on their surface?
What is the name of the complex formed by these two molecules?
Major histocompatability complex
Peptide-MHC complex
What are the X2 types of MHC molecule?
How do these differ?
MHC 1 = single chain = found on all cells
MHC 2 = alpha/beta heterodimer = found on entire presenting cells only
What is the area at the top of the MHC which the antigen peptide fragment sits in called?
Peptide binding groove
Where do the peptides displayed on the MHC moelcuels come from in:
A) MHC class 1 molecules B) MHC class 2 molecules
A) MHC class 1 molecules = peptides displayed are derived from proteins that cell is currently synthesising (so if a virus hijacks the cell machinery to synthesis it’s own proteins for reproduction, these will be displayed)
B) MHC class 2 molecules = peptides displayed are derived from antigens that the cell has phagocytosed and broken down.
Where is the gene located which encodes for the MHC classes?
What is this region called?
On the P arm of chromosome 6
The human leukocyte antigen region
What are the X3 possible HLA 1 genes (code for MCH 1)?
HLA A
HLA B
HLA C
What are the X3 possible HLA 2 genes (code for MCH 2)?
HLA DP
HLA DQ
HLA DR
What defines a T-cell?
Having a T-cell receptor!
What joins the X2 chains of a T-cell?
Disulphide bonds
Do T-cells undergo affinity maturation?
No, only B-cells.
They both however undergo gene rearrangement.
What class of MHC presented peptides do CD8 (cytotoxic) T-cells interact with?
Their CD8 receptor interacts with the conserved (non-peptide binding region) of MHC 1 molecules.
What class of MHC presented peptides do CD4 (T-helper) T-cells interact with?
Their CD4 receptor interacts with the conserved (non-peptide binding region) of MHC 2 molecules.
How many signals are needed to activate T-cells?
X2
1) MHC-peptide complex
2) co-stimulators signal
Give X2 examples of second signals / co-stimulators signals displayed by antigen presenting cells?
CD80
CD86
What do second signals such as CD80 or CD86 bind to on the T-cell which (when they have both bound together) sends a signal to the T-cell to activate it?
A molecule called CD28
How do CD8 T-cells work?
They are cytotoxic T-cells therefore they bind to antigen presenting cells and release cytotoxic cytokines to kill it.
What different kinds of effector T-cells can CD4 (T-helper) cells differentiate into once activated?
What cytokines do each secrete?
Th1 = secrete IFN gamma, IL2 Th2 = IL2, 4, 5, 13 Th17 = IL 17, 21, 22 Treg = IL10, TGF beta
What do activated Th1 T-helper cells do?
They secrete:
INF gamma = promote macrophage activation and direction to sites of infection
IL2 = helps CD8 cytotoxic T-cell differentiation
What do activated Th2 T-helper cells do?
They secrete IL2, 4, 5 and 13 which helps B-cells to divide/class switch/affinity mature/differentiate into plasma cells.
What do activated Th17 T-helper cells do?
They secrete IL17, 21 and 22 which attract neutrophils to the site of infection via chemotaxis.
What do activated T-reg cells do?
They secrete IL10 and TGF beta (but also work via cell to cell contact) which mainly SUPPRESSES the antigen presenting cell activity therefore mediates the inflammatory response.
