T cell effector functions and the MHC Flashcards Preview

Theme 7 - Infection, Immunity and Inflammation > T cell effector functions and the MHC > Flashcards

Flashcards in T cell effector functions and the MHC Deck (22):

Which T cells are depleted in HIV/AIDS?

CD4+ T cells


Define MHC restriction.

T cells recognise pathogens by recognising pathogenic peptide fragments on MHC molecules. They can not recognise whole antigen, only a combination of antigen peptide with MHC.


Describe the structure of MHC molecules.

MHC molecules are transmembrane proteins that contain a specific peptide binding groove to which the pathogenic peptide is held in for presentation to T cells.

MHC class I is expressed on all nucleated cells.

MHC class I consists of 3 alpha subunits and 1 Beta-2 microglobulin.

MHC class II is expressed on APCs such as Monocytes/Macrophages, Dendritic cells and B cells.

MHC class II consists of 2 alpha subunits and 2 beta subunits Disulphide bonds


Give an example of a human body cell that does not express MHC Class I.

Erythrocytes - Lack a nucleus


Where are the genes that encode both classes of MHC found?

On the short arm of chromosome 6.


How many polymorphic genes are involved in encoding an MHC class I molecule?

There are 3 HLA genes:



Describe the structure of the TCR.

Heterodimer of either alpha-beta or gamma-delta subtypes.

Consist of variable and constant domains

V-alpha, C-alpha, V-beta, C-beta


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How many different genes make up the light chain of the TCR?

V, J and C

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How many different genes make up the heavy chain of the TCR?

V, D, J and C

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True or False: Interaction of peptide-MHC with TCR is sufficient to activate a naive T cell

False - 2 signals are required

TCR -> Peptide-MHC interaction only provides signal 1.

Signal 2 comes from co-stimulation by T cell CD28 and APC CD86 interaction.


What two events cause upregulation of co-stimulatory molecules like APC CD86 and T cell CD28?

Infection and Inflammation.


MHC class I presents peptide to what cell?

CD8+ T cell


MHC class II presents peptide to what cell?

CD4+ T cell


Describe the killing mechanisms of CD8+ cytotoxic T cells.

  1. CD8+ FasL binds to the infected cell's Fas receptor, which activates caspases and the apoptotic cascade.
  2. Release of TNF-alpha that binds to receptors on the infected cell to initiate apoptosis
  3. Release of Perforins which allow granzymes to invade the infect cell and induce apoptosis.


How are Th1 cells produced?

Exposure of naive T cells to IL-12


 How are Th2 cells produced and under what circumstances are they present in high levels?

Exposure of naive T cells to IL-4

In allergy and asthma


How are Th17 cells produced?

Exposure of naive T cells to TGF-ß and IL-2


How are Treg cells produced and what key process are they involved in?

Exposure of naive T cells to TGF-ß and IL-10

Crucial in Immune Tolerance


How do Th1 cells help other immune cells?

Release of IL-2 and IFN-gamma to stimulate CD8+ T cells to proliferate, differentiate and become activated.


Release of IFN-gamma also activates Macrophages


How do Th2 cells help B cells?

Produce cytokines: IL-2, IL-4, IL-5 and IL-13

These cytokines stimulate class switching to IgG, affinity maturation, antibody production, proliferation and differentiation.


How do Th17 cells fight extracellular pathogens?

Release of IL-17 and Il-22 cytokines, which stimulate Epithelial cells and Fibroblasts to produce anti-microbial peptides, improe wound healing and upregulate chemotaxis to recruit neutrophils.




What is the function of Treg cells?

Production of anti-inflammatory cytokines - TGF-ß,IL-10 and through cell-cell contact, suppress activation of APCs, antibody and cytokine production, as well as control of the function of NK and CD8+ T cells.