1. Difficulties often occur when tissues or organs are
    transplanted from one person to another because the
    (1) transplanted structures cannot produce new cells
    (
    2)
    rate of mitosis differs between the two people
    involved
    (3) introduction of a foreign substance causes the
    formation of antibodies
    (4) two people often have the same blood type

Verified Answer :

Final answer:

The rejection of transplanted organs is primarily due to the immune system's response to foreign tissues, particularly related to different MHC I molecules between donors and recipients.


Explanation:

Different MHC I molecules between donor and recipient cells can lead to rejection of a transplanted organ or tissue due to the recipient's immune system recognizing the donor tissue as foreign and triggering an immune response. This rejection process involves major histocompatibility complex markers MHC I and MHC II, specifically human leukocyte antigens (HLAs), playing a critical role.


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