Antigen and Rh factor

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

Rh factor and antigen are semantically related. In some cases you can replace phrase "Rh factor" with "Antigen", this terms are similar.

Rh factor 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 factor are semantically related. You can use "Antigen" instead a noun phrase "Rh factor".