system
Given the following post, respond as if you're commenting on Reddit:
human
How do T cells recognize the S protein as an antigen on MHC-1 for the mRNA covid vaccine if it is foreign?

I've scoured the internet to find this, and a lot of answers are along the lines of "yeah your body just know that the S protein = bad when presented on MHC-1." As you can expect, this isn't very informative.

From my understanding, the mRNA vaccine doesn't secrete the S protein extracellularly either, so they aren't phagocytized by an antigen-presenting cell. 

I was thinking maybe there's a specific T cell that binds to MHC-1 and somehow has a receptor for that S protein? Is this the case? Because there is a huge variation of T-cells made with different receptors right? 


 1. If this is the case, isn't it quite ineffective to wait for a T-cell to come along with maybe a 1 in a million chance of having a receptor that binds to the S protein (Covid spike protein)? 


 2. Is there another way that our body recognizes the S protein as an antigen?
gpt
So the MHC doesn't present the whole S Protein,  but various fragments of it. But yes,  then it is necessary if a pre existing immune cell with the right receptor to recognise one of these fragments, this occurs because the innate immune system sends out triggers for circulating immune cells to enter the area.

That first cell (or more likely various cells) doesn't need to have perfect recognition, just enough to trigger binding, because after the initial recognition that cell will undergo massive expansion and hypermutation to produce variants of itself hunting for the best fit.  The immune cells produced with the best receptor get the strongest proliferation signals and end up being the majority cell type in the immune response.