Rhesus (noun)

1. A substance that is found on the surface of red blood cells in some people and can cause a reaction when it comes into contact with the blood of someone who does not have it.
2. A type of antigen found on the surface of red blood cells that can trigger an immune response if it is introduced into the bloodstream of an individual who lacks it.

Origin:

Named after the rhesus monkey, which was used in the early studies that identified the presence of this antigen on the surface of red blood cells.

Examples:

1. The rhesus antigen can cause a dangerous condition known as hemolytic disease of the newborn.
2. The rhesus blood group is one of the most important blood groups in transfusion medicine.
3. The rhesus factor is inherited from one's parents.
4. The rhesus negative blood is needed for certain medical treatments.
5. The rhesus incompatibility can cause complications during pregnancy.