The importance of dendrittic cells in activating T-cells

[strikken]

Hi!

 

I'm currently studying immunology and am quite confused about how our body can eliminate an viral infection.

As far as I've heard, the dendritic cells are important in this because they can present extracellular patogens as MHC class I and thereby activate CD8-T-cells.

But how could that eliminate the intracellular viruses when the dendrittic cells reacted on an extracellular patogen in the first place?

 

Or is the explanation that the extracellular fragment could be a viral particle?

 

Furthermore, how could MHC class I activate B-cells to undergo differentiaton to plasma B-cells? Is it so that we don't have antibodies against virus, and that they are primarly killed by Natural Killer cells?

 

I asked my professor, and he mentioned that B-cells can present viruses as MHC-class II, so that the B-cell could be activated by an CD4-T-helper cell. But how can a CD4-T-helper cell be complementary to this B-cell when CD4-T-cells are activated from MHCII presenting cells presenting MHCII only after taking up a extracellular patogen?

 

Happy for all help,

 

friendly regards

"Strikken"

Edited May 24, 2012 by strikken

[edsonrao]

Hi!

 

I'm currently studying immunology and am quite confused about how our body can eliminate an viral infection.

As far as I've heard, the dendritic cells are important in this because they can present extracellular patogens as MHC class I and thereby activate CD8-T-cells.

But how could that eliminate the intracellular viruses when the dendrittic cells reacted on an extracellular patogen in the first place?

 

Or is the explanation that the extracellular fragment could be a viral particle?

 

Furthermore, how could MHC class I activate B-cells to undergo differentiaton to plasma B-cells? Is it so that we don't have antibodies against virus, and that they are primarly killed by Natural Killer cells?

 

I asked my professor, and he mentioned that B-cells can present viruses as MHC-class II, so that the B-cell could be activated by an CD4-T-helper cell. But how can a CD4-T-helper cell be complementary to this B-cell when CD4-T-cells are activated from MHCII presenting cells presenting MHCII only after taking up a extracellular patogen?

 

Happy for all help,

 

friendly regards

"Strikken"

 

A very basic explanation could be:

 

Dendritic cells (DC), as other APCs (antigen presenting cell), are specialized in presenting antigens, what promptly brings to our mind the class II MHC context. Apart from this, like all other nucleated cell, they also can be infected by pathogens and present their epitopes in a class I MHC context. What make these cells so cool, is that they are usually located in strategic points of our body in a way to be the first ones to fight a pathogen. A DC can be killed by a citotoxic TCD8 cell, but it's more probable that a DC, that has seen a pathogen, encounter a TCD4 (is more often in our blood stream). At this point the DC will present epitopes of the pathogen to the limphocyte TCD4 via class II MHC context leading to diferentiation of this naive T cell into a helper T cell making a bridge with the adaptive immunity.

 

The B cell is able to take up a full virus particle, process and produce antibodies against its parts, but the "cream de la cream" of the humoral response happens when a T helper CD4 cell encounter a B cell presenting viral epitopes via MHCII that is recognized by the T cell. A couple of other co-stimulation is needed as CD40-CD40L and then the B cell is iduced to diferentiate in plasma cells when they will secret a great amount of antibody with high avidity to that epitope.

 

Hope it could have helped.

 

Regards.