HIV and CD4/CD8 T cells

[shigella123]

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I don't understand this clearly:

Cytotoxic CD 8 T cells are the one mainly responsible for killing viruses, but then the HIV attacks CD 4. So, HIV attacks CD 4 and then CD 8 comes to kill the infected cell?

 

[Handinhand]

Well, first HIV is going to infect your dendritic cells (epithelial antigen presenting cells), which are then going to migrate to their closest lymph node and "present" the virus to the CD4 cells, when in reality they'll become infected.

Once that happens, you might get some cytotoxicity from CD8 cells, but not a great response because HIV becomes a chronic infection so you're obviously not removing the virus well enough.

 

[dyspareunia]

I don't understand this clearly:

Cytotoxic CD 8 T cells are the one mainly responsible for killing viruses, but then the HIV attacks CD 4. So, HIV attacks CD 4 and then CD 8 comes to kill the infected cell?

HIV can downregulate MHC-1 expression, so NK cells end up being of primary importance.

 

[H Y F R]

I echo everything here. Also, don't forget that the virus requires the CCR5/CXCR4 chemokine receptor to invade host cells. These receptors are found only on APCs and CD4+ cells, which explains why these cells are the predominant mediators of the disease. And, as stated above, HIV (and most viruses) down-regulate MHC-1 receptors, rendering targeting by NK-cells ineffective.

 

[tantacles]

I echo everything here. Also, don't forget that the virus requires the CCR5/CXCR4 chemokine receptor to invade host cells. These receptors are found only on APCs and CD4+ cells, which explains why these cells are the predominant mediators of the disease. And, as stated above, HIV (and most viruses) down-regulate MHC-1 receptors, rendering targeting by NK-cells ineffective.

Downregulating MGC makes NK cells work BETTER than other types because NK cells don't need specific activation. The whole point of NK cells is that they attack anything with downregulated MHC-1. Downregulating MHC-1 WOULD make cytotoxic cells less effective, but certainly wouldn't have the same effect on NK cells.

 

[H Y F R]

Downregulating MGC makes NK cells work BETTER than other types because NK cells don't need specific activation. The whole point of NK cells is that they attack anything with downregulated MHC-1. Downregulating MHC-1 WOULD make cytotoxic cells less effective, but certainly wouldn't have the same effect on NK cells.

My bad on that. You're right. Went off the cuff there.

 

[tantacles]

My bad on that. You're right. Went off the cuff there.

It's all good. This happens to me just about every day. This is the one time out of 100 that I'm right.

 

[notbobtrustme]

Downregulating MGC makes NK cells work BETTER than other types because NK cells don't need specific activation. The whole point of NK cells is that they attack anything with downregulated MHC-1. Downregulating MHC-1 WOULD make cytotoxic cells less effective, but certainly wouldn't have the same effect on NK cells.

viruses get around this by putting up dummy MHC-I that fools CD8s and NK cells.