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</span>Most cells of the body have self markers on the surface of their cell called the major histocompatibility complex (MHC). The MHC allows cells of the immune system to recognize the cell as part of our self.<span>system to recognize the cell as part of ourself.</span>
It would be Newton's "3rd" Law that explains why my hands hurt when I clap loudly, since this states that every action as an equal and opposite reaction.
