Which (if any) of the following statements about the major histocompatibility complex (MHC) is not correct?
If all of the statements are correct choose the last answer.
a. all human cells, including red blood cells, possess MHC I
b. each person has a unique MHC (except for identical twins).
c. in order for organ transplantation to be successful, the organ donot and the recipient must have a similar MHC
d. the MHC allows the immune cells to differentiate the host cells from "foreign" cells
e. all of the above statements about the MHC are correct.

MHC is a group of genes involved in the immunological recognition of self (cells of the organism) and nonself (exogenous agents), it's found un all nucleated cells of the body, this means it can't be found in red blood cells because they lack a nucleus.

MHC genes are highly polymorphic, this means different alleles exist in different individuals except for identical twins that share the same genetic profile.

When transplantation happens, the organ donor and receiver need to have similar MHC, otherwise, the receptor's dendritic cells will recognize the new organ as non-self molecules. Since MHC are highly polymorphic, choosing a sibling as a donor increases the chances to find a match since the receptor shares genetic information with the donor.

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