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It is a medically recognized fact that people with the same immune characteristics do not exist, in other words, everyone's body will have an immune rejection response to other people's cells.
This conclusion has already been recognized.
But think about it, it seems that no institution has conducted enough experiments to verify it.
This is also normal.
Generally, contact with other people's cells is accomplished through blood transfusions or organ transplants; with the same blood type, the immune rejection response to the transfusion is not significant, and even if cases of no immune rejection reaction exist, without detailed testing, it would not be known.
Organ transplants are even less common, and even if subsequent immune rejection reactions are very mild, they are mostly attributed to the effects of drugs or the strong recovery capabilities of the patients.