When does da antigen present on MHC-1 groove? is it always or only when abnormal

[sylhet]

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we all know that only peptide fragments can be loaded on the groove of a MHC molecule. I am stucked at some point understanding when they present the peptide fragments on that groove of MHC-1 molecule.

Does a normal functioning nucleated cell always presents it self antigen fragment to the MHC-1 so that T-cells do not recognize it as a non-self and not kill it??

OR

only when the cell is infected (suppose intracellular pathogen, virus), or the cell altered as in case of tumor cells , the self MHC-1 presents the abnormal antigen fragment on its groove so that now the T cells can recognize the antigen fragment as non-self and kill it????😕😕

 

[ProtossCarrier]

always,but i could be wrong.

 

[Mr hawkings]

always,but i could be wrong.

You're right.

 

[unsung]

we all know that only peptide fragments can be loaded on the groove of a MHC molecule. I am stucked at some point understanding when they present the peptide fragments on that groove of MHC-1 molecule.

Does a normal functioning nucleated cell always presents it self antigen fragment to the MHC-1 so that T-cells do not recognize it as a non-self and not kill it??

OR

only when the cell is infected (suppose intracellular pathogen, virus), or the cell altered as in case of tumor cells , the self MHC-1 presents the abnormal antigen fragment on its groove so that now the T cells can recognize the antigen fragment as non-self and kill it????😕😕

Always, 'cuz when it's a tumor cell there's decreased MHC-1 presentation, which signals NK cells to kill it. So if it didn't always present, there wouldn't be such a thing as decreased presentation. I think.

 

[FutureInternist]

Always, 'cuz when it's a tumor cell there's decreased MHC-1 presentation, which signals NK cells to kill it. So if it didn't always present, there wouldn't be such a thing as decreased presentation. I think.

All antigens (self or foreign) that are derived from the cell's nuclear apparatus end up on the MHC I molecule. So normally only self antigens will show up on MHC I and the T8 cell will let it be. If however you have an infected cell and the nucleus has been "invaded" then the cell starts making self and non-self antigens that all end up on MHC I. Now when a T8 cell sees a non-self antigen on an MHC I, it knows it's too late and kills it.

 

[bbydoc]

we all know that only peptide fragments can be loaded on the groove of a MHC molecule. I am stucked at some point understanding when they present the peptide fragments on that groove of MHC-1 molecule.

Does a normal functioning nucleated cell always presents it self antigen fragment to the MHC-1 so that T-cells do not recognize it as a non-self and not kill it??

OR

only when the cell is infected (suppose intracellular pathogen, virus), or the cell altered as in case of tumor cells , the self MHC-1 presents the abnormal antigen fragment on its groove so that now the T cells can recognize the antigen fragment as non-self and kill it????😕😕

that's correct although the last bit is not necessary, CD8 wont do anything even if the MHC-I groove is empty. only if there are foreign fragments in the groove or there is a decrease in MHC-I will the immune system react.
So why do we express our own antigen-fragments in the MHC-I groove anyway if thats not necessary???
It is necessary in the thymus to educate your CD8 cells not to go rambo on your own cells in the periphery.

In addition some clever viruses and cancer cells try to evade the immunesystem just by inhibiting MHC-I synthesis so that CD8 cells won't disturb them. --> But NK-cells are clever and recognize the decrease in number of MHC-Is and kill those cells.
But there are some viruses and cancer cells that are even cleverer than that and not only inhibit MHC-I synthesis but also produce recoil molecules that resemble MHC-I to fool NK-cells as well as CD8 cells.
But a competent immune system outsmarts even this mechanism of immune-evasion by recognizing the recoil molecules and producing IgG aginst it. and NK-cells have receptors for IgG (which gives NK-cells some specificiy) so get those bastards anyhow 🙂

 

[sylhet]

thanks a lot for ur answer. THANks very much to everyone for ur concern. it really helped me. now i got it correct. thanks everyone again

 

[Bob101]

that's correct although the last bit is not necessary, CD8 wont do anything even if the MHC-I groove is empty. only if there are foreign fragments in the groove or there is a decrease in MHC-I will the immune system react.
So why do we express our own antigen-fragments in the MHC-I groove anyway if thats not necessary???
It is necessary in the thymus to educate your CD8 cells not to go rambo on your own cells in the periphery.

In addition some clever viruses and cancer cells try to evade the immunesystem just by inhibiting MHC-I synthesis so that CD8 cells won't disturb them. --> But NK-cells are clever and recognize the decrease in number of MHC-Is and kill those cells.
But there are some viruses and cancer cells that are even cleverer than that and not only inhibit MHC-I synthesis but also produce recoil molecules that resemble MHC-I to fool NK-cells as well as CD8 cells.
But a competent immune system outsmarts even this mechanism of immune-evasion by recognizing the recoil molecules and producing IgG aginst it. and NK-cells have receptors for IgG (which gives NK-cells some specificiy) so get those bastards anyhow 🙂

I think the NK cell is a pretty cool guy. eh kills invadrs and doesnt afraid of anything.