UW immuno q

[MudPhud20XX]

Could we discuss this q?

A 45 yr old male with fulminant viral hepatitis receives a liver transplant. One week after his surgery, the patient develops a desquamating skin rash and bloody diarrhea. Imaging studies reveal multiple ulcerations of the intestinal mucosa. Which of the following is the most likely cause of this pt's current condition?

A. prerformed antiboides against graft ABO antigens
B. host B-cell sensitization against graft MHC antigens
C. host T-cell sensitization against graft MHC antigens
D. graft B-cell sensitization against host MHC antigens
E. graft T-cell sensitization against host MHC antigens

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[TheNsg300]

I wud go wit E,,GVHD following liver transplantation,,triad of rash, jaundice and diarrhea,,because of targeting of sites of inflammation in the host following cytotoxic drugs, infections,,to suppress immunity prior to grafting,,
N.B. GVHD not only after Bone Marrow transplantation,,some immune cells also reside in RES(liver, spleen)

 

[worldbeater]

I think it's C. I've seen this question on UWorld, I don't remember the answer off hand but this is how I would approach it.

The antigen is going to be from a foreign substance, so that would make it a graft antigen. Knock out D & E.

Then, we are talking about a immune response, which has two arms, humoral (bacterial/b-cell) mediated or cell mediated (t-cell). Humoral is used in the blood for destruction against bacteria. Cell mediated is used for tissue against non bacteria. It's a liver transplant, so it's tissue, making it cell mediated.

Cell mediated immunity means T-cell, so knock out B, we are left with A & C. C has the nicest fit, "host t-cell sensitization against graft MHC antigens"

 

[seminoma]

I think it's C. I've seen this question on UWorld, I don't remember the answer off hand but this is how I would approach it.

The antigen is going to be from a foreign substance, so that would make it a graft antigen. Knock out D & E.

Then, we are talking about a immune response, which has two arms, humoral (bacterial/b-cell) mediated or cell mediated (t-cell). Humoral is used in the blood for destruction against bacteria. Cell mediated is used for tissue against non bacteria. It's a liver transplant, so it's tissue, making it cell mediated.

Cell mediated immunity means T-cell, so knock out B, we are left with A & C. C has the nicest fit, "host t-cell sensitization against graft MHC antigens"

It's E. This is GVHD.

Also humoral and cell-mediated can be against both bacteria and host tissue.

 

[worldbeater]

It's E. This is GVHD.

Also humoral and cell-mediated can be against both bacteria and host tissue.

k, I'll take you at your word.

It can be, but 90% of the time, the two types of immunity breakdown how I mentioned it above. This is probably one of the questions that falls out of that description.

 

[seminoma]

k, I'll take you at your word.

It can be, but 90% of the time, the two types of immunity breakdown how I mentioned it above. This is probably one of the questions that falls out of that description.

I think you might need to review your immunology.

The most general distinction between humoral and cell-mediated is the location of the antigen. Intracellular = cell-mediated. Extracellular = humoral. The type/source of antigen doesn't make much of a difference.

And in regard to OP's question, if this was a host-mediated reaction (i.e. recipient T cells), then the patient would more likely be presenting with signs of liver failure rather than rash, bloody diarrhea, and intestinal ulcerations. Classically GVHD involves skin and intestine (i.e. rash and diarrhea) and presents within a week or two. Of course there's also the pattern recognition aspect of this question. Any liver or BM transplant should bring GVHD into your differential. If they wanted to test acute vs chronic rejection they would give you a different solid organ and they would have histologic descriptions of the transplanted organ. And finally, acute transplant rejection has both humoral and cell-mediated components. So the distinction would be Tcells or Bcells, and not humoral and cell-mediated.

 

[worldbeater]

I think you might need to review your immunology.

The most general distinction between humoral and cell-mediated is the location of the antigen. Intracellular = cell-mediated. Extracellular = humoral. The type/source of antigen doesn't make much of a difference.

Right I agree with you, in terms of location.

Humoral -> extracellular -> out of the cell -> meaning the blood

Cell mediated -> intracellular -> meaning within the cell

Yeah, regarding the source antigen, I need to look it up again, I don't have that down 100%.