We all know that if normal cell contains virus inside it, normal cell has mechanism inside it that can detect that it has abnormality inside(virus) and what it will do is present the virus's protein(antigen) with MHC I on its surface, so T-cytoxic cells can kill it.

But cancer cells don't have virus inside. They still look healthy. I mean the cell itself has different proteins(derived from mutation), but cell itself thinks that it's healthy. So would it put anything on its surface with the MHC I ?

  • If the answer is no, then we got a problem, as it would never, ever be recognized by T-cell to kill it.

  • If the answer is yes, I guess, it would just put its modified protein, though, in that case, that means that every cell(in our body, even normal ones), they all put their protein representations on their surface. Because if cancer cell(which thinks it's healthy put it, then every cell which is also healthy should put it, seems logical)

Maybe my question should be: What is MHC I exactly ?

In case of normal cells(healthy ones), only MHC I is put on the surface and MHC I is proteins taken from within the cell.

In case of the cell that contains the virus, MHC I is the proteins from within the cell that aren't part of the virus protein. So here on the surface, it puts MHC I and virus protein(antigen) separately(MHC I + antigen).

In case of cancer cell, what is put on the surface ? just MHC I (which are modified proteins within the cell) or we also have somehow MHC I + antigen, but I don't understand how we would have MHC I + antigen combination as the cell doesn't know that it has antigen(thinks it's normal).

What do you think ? I'd appreciate the clear explanation.

  • 2
    $\begingroup$ This is a really big field. I think that there is a lot of complexity in how the immune system recognizes cancer cells. Yeah there are specific epitopes that get displayed, but I'd suggest just googling "how does the immune system recognize cancer cells", and you will get lots of helpful results like this. $\endgroup$ Nov 21, 2022 at 21:08
  • $\begingroup$ I'm voting to close this as "Needs more focus." @MaximilianPress is correct, this is a huge field, and even a simplified answer would need to be textbook chapter-length in order to be complete. $\endgroup$
    – MattDMo
    Nov 22, 2022 at 15:07


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