Proteins that tag pathogens for destruction by immune cells are called a. antibodies. b. antigens. c. histamines. d. interferons.

Antigen

The antigen are proteins in the cells of the body.Out of over 100 different antigens that have been identified, there are six that have been shown to be the most important in organ transplantation. Of these six antigens, we inherit three from each parent. It is rare to get a six-antigen match between two people, especially if they are unrelated. HLA(human leucocyte antigen) typing is done before the transplant to ensure high probability of success.

A person can make antibodies against another person’s HLA antigens.  If a recipient has strong antibodies against a donor’s HLA, the risk of rejection is high and a donor would be declined for that recipient. so the type of antigens are tested for the compatibility before a transplant to ensure high probability of success and lower the rate of rejection.

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the answer is d (apex) good luck : ))