Antigen and Rh

Antigen noun - Any substance (as a toxin or enzyme) that stimulates an immune response in the body (especially the production of antibodies).

Rh and antigen are semantically related. In some cases you can replace term "Rh" with "Antigen", this nouns are similar.

Rh noun - A blood group antigen possessed by Rh-positive people; if an Rh-negative person receives a blood transfusion from an Rh-positive person it can result in hemolysis and anemia.

Antigen and rh are semantically related. You can use "Antigen" instead a noun "Rh".