(Kidney) Transplant question

[anbuitachi]

Since in organ transplantations [kidney] the MHC class II are on APCs and since those APCs die, and in the immune system, reactions happen mostly toward class IIs. since those APCs are dead after a while, why is there still so much reaction of host attacking the graft? For HLA typing they check MHC class II. Why do so if MHC class II willl just disappear after a few months?

Mainly concerned about organ transplants, not BM, or blood. Thanks!!!

---

Members don't see this ad.

 

[Jamiu22]

Hi, just a question about transplanting. If ie a kidney is transplanted, and since donor cells are no longer produced and eventually die after like few months [dendritic cell etc]. Why is the donor organ still attacking host and vice versa for rest of pts life? [more confused about donor attacking host] Thanks!

I'm think I understand your question - so let me take a stab at it.

First you have to identify correctly the donor and the recipient organ and how it interplays with immune system. We can receive different of organs (doesn't have it's own immune function), or on the other hand receive a bone marrow transplant (has it's own immune function)...

So the only time a donor transplant will attack a host is when you have bone marrow transplant, and now the WBCs from the donor confers immunity of the person it was donated from.... and the recipient in this case would be seen as foreign... and as you recall, the WBCs do this by looking at the HLA (human leukocyte antigen) on the cells its surveying to identify it as self or non-self. So if your receive blood cells that's not urs, then every organ will now be denoted as foreign and attacked....

Now to get back to your question.... since you are receiving a foreign organ... your immune system (WBCs) will see the kidney as foreign and then try to attack it (the degree of attack on that kidney would depend heavily on how much your HLA matches)... the closer the match, the less rejection your immune system would have for that received organ. All cells have antigens, and until the kidney cells die off completely and is removed from your body, you'll always reject it.

 

[anbuitachi]

I'm think I understand your question - so let me take a stab at it.

First you have to identify correctly the donor and the recipient organ and how it interplays with immune system. We can receive different of organs (doesn't have it's own immune function), or on the other hand receive a bone marrow transplant (has it's own immune function)...

So the only time a donor transplant will attack a host is when you have bone marrow transplant, and now the WBCs from the donor confers immunity of the person it was donated from.... and the recipient in this case would be seen as foreign... and as you recall, the WBCs do this by looking at the HLA (human leukocyte antigen) on the cells its surveying to identify it as self or non-self. So if your receive blood cells that's not urs, then every organ will now be denoted as foreign and attacked....

Now to get back to your question.... since you are receiving a foreign organ... your immune system (WBCs) will see the kidney as foreign and then try to attack it (the degree of attack on that kidney would depend heavily on how much your HLA matches)... the closer the match, the less rejection your immune system would have for that received organ. All cells have antigens, and until the kidney cells die off completely and is removed from your body, you'll always reject it.

Oh so only BM transplants attack the host?

 

[madchemist89]

Oh so only BM transplants attack the host?

It is my understanding that any transplant containing T cells can attack the host. However, in most circumstances the host's immune response against the transplanted tissue and cells is far greater than anything that the few T cells in the transplant can mount against the host. In this situation, transplant rejection is of concern because the host is immunocompetent.

Bone marrow transplants are a special case because the host's bone marrow has been irradiated, killing off any host immune cells that could mount a response against the graft. Because the host is left defenseless, any T cells remaining in the graft can mount a response against the host.

 

[withrye]

It is my understanding that any transplant containing T cells can attack the host. However, in most circumstances the host's immune response against the transplanted tissue and cells is far greater than anything that the few T cells in the transplant can mount against the host. In this situation, transplant rejection is of concern because the host is immunocompetent.

Bone marrow transplants are a special case because the host's bone marrow has been irradiated, killing off any host immune cells that could mount a response against the graft. Because the host is left defenseless, any T cells remaining in the graft can mount a response against the host.

In addition, liver and non-irradiated blood transfusions can also hold a sizable reservoir of T cells. As such, any immunocompromised host receiving BM, liver, or blood transfusion is at risk for GVH.

You tend to see transplant rejection in the donating organ itself, whereas GVH manifests itself in the liver, on the skin, or in the GI tract of the host.

 

[anbuitachi]

Ok so I got info that teh question is actually supposed to be:

Since in organ transplantations [kidney] the MHC class II are on APCs and since those APCs die, and in the immune system, reactions happen mostly toward class IIs. since those APCs are dead after a while, why is there still so much reaction of host attacking the graft? For HLA typing they check MHC class II. Why do so if MHC class II willl just disappear after a few months?

 

[withrye]

Ok so I got info that teh question is actually supposed to be:

Since in organ transplantations [kidney] the MHC class II are on APCs and since those APCs die, and in the immune system, reactions happen mostly toward class IIs. since those APCs are dead after a while, why is there still so much reaction of host attacking the graft? For HLA typing they check MHC class II. Why do so if MHC class II willl just disappear after a few months?

MHC-I needs to be matched as well. Every nucleated cell presents MHC-I, so if a donated organ doesn't present matching MHC-I, the T cells will attack that as well.

 

[preDoGuy24]

Ok so I got info that teh question is actually supposed to be:

Since in organ transplantations [kidney] the MHC class II are on APCs and since those APCs die, and in the immune system, reactions happen mostly toward class IIs. since those APCs are dead after a while, why is there still so much reaction of host attacking the graft? For HLA typing they check MHC class II. Why do so if MHC class II willl just disappear after a few months?

Reactions do not occur "mostly toward class IIs" in the immune system. Class I is very important in graft rejection, I suggest going back and reading hyperacute, acute, and chronic graft rejection.

Hyperacute= preformed antibodies, immediate reaction
Acute= Type II and IV hypersensitivity, host against graft-days to weeks to develop
chronic=irreversible, think fibrosis and blood vessel damage.

You are mixing concepts, Graft versus host and graft rejection are not the same thing.

 

[anbuitachi]

oh thanks everyone! i'll do more reading

 

[tiedyeddog]

MHC-I needs to be matched as well. Every nucleated cell presents MHC-I, so if a donated organ doesn't present matching MHC-I, the T cells will attack that as well.

This is my understanding, too.