Based on my research on how mRNA vaccines (specifically for COVID-19) work:

An mRNA sequence, that contains the sequence of the coronavirus spike protein, is absorbed by some cells. These cells now produce foreign coronavirus spike protein. These cells then present some of the produced foreign spike protein on their surface via MHC I complexes so that they can activate a cytotoxic T cell and cause it to produce lots of copies of itself (cell-mediated immune response). Some of the foreign spike proteins are also released from the transfected cells which allow for B cells to activate a humoral immune response and for professional antigen-presenting cells to present the foreign spike protein on MHC II complexes to activate helper T cells.

My Question:

As far as I understand it, once a cytotoxic T cell encounters a cell that has a foreign protein presented on an MHC I complex, the T cell kills the cell that has presented the foreign protein before it leaves. This means the cells transfected with mRNA through the COVID-19 vaccine (even though a coronavirus hasn't actually hijacked them) will eventually be killed by cytotoxic T cells that encounter them since they are presenting foreign spike proteins on their surface. Is this not toxic for the body since it is killing your own cells? Or does the fact that the mRNA sequences are not self-replicating contain these cell deaths to only the transfected cells and only a few cells die in this process so that the vaccine is not toxic overall?

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    $\begingroup$ If you can cite some sources for your answer edit you can feel free to make that into a self-answer, nothing wrong with self-answers on StackExchange. $\endgroup$ – Bryan Krause Nov 22 at 18:24

According to the person who made this video's response to my comment asking this question, the transfected cells are killed by cytotoxic T cells, but the amount of transfected cells dying is not enough to cause irreparable harm since the cells regenerate themselves fairly quickly through division. Plus, the acquired cell-mediated in addition to humoral immunity is well worth the risk of an mRNA vaccine over a standard protein vaccine (which only leads to humoral immunity). If anyone has a better answer than this please let me know.

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